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4427424

10.1038/NATURE03647

Aerodynamics of the hovering hummingbird

Despite profound musculoskeletal differences, hummingbirds (Trochilidae) are widely thought to employ aerodynamic mechanisms similar to those used by insects. The kinematic symmetry of the hummingbird upstroke and downstroke has led to the assumption that these halves of the wingbeat cycle contribute equally to weight support during hovering, as exhibited by insects of similar size. This assumption has been applied, either explicitly or implicitly, in widely used aerodynamic models and in a variety of empirical tests. Here we provide measurements of the wake of hovering rufous hummingbirds (Selasphorus rufus) obtained with digital particle image velocimetry that show force asymmetry: hummingbirds produce 75% of their weight support during the downstroke and only 25% during the upstroke. Some of this asymmetry is probably due to inversion of their cambered wings during upstroke. The wake of hummingbird wings also reveals evidence of leading-edge vortices created during the downstroke, indicating that they may operate at Reynolds numbers sufficiently low to exploit a key mechanism typical of insect hovering. Hummingbird hovering approaches that of insects, yet remains distinct because of effects resulting from an inherently dissimilar—avian—body plan.

Nature

8885017

10.1093/ICB/ICR016

The tubercles on humpback whales' flippers: application of bio-inspired technology.

The humpback whale (Megaptera novaeangliae) is exceptional among the large baleen whales in its ability to undertake aquabatic maneuvers to catch prey. Humpback whales utilize extremely mobile, wing-like flippers for banking and turning. Large rounded tubercles along the leading edge of the flipper are morphological structures that are unique in nature. The tubercles on the leading edge act as passive-flow control devices that improve performance and maneuverability of the flipper. Experimental analysis of finite wing models has demonstrated that the presence of tubercles produces a delay in the angle of attack until stall, thereby increasing maximum lift and decreasing drag. Possible fluid-dynamic mechanisms for improved performance include delay of stall through generation of a vortex and modification of the boundary layer, and increase in effective span by reduction of both spanwise flow and strength of the tip vortex. The tubercles provide a bio-inspired design that has commercial viability for wing-like structures. Control of passive flow has the advantages of eliminating complex, costly, high-maintenance, and heavy control mechanisms, while improving performance for lifting bodies in air and water. The tubercles on the leading edge can be applied to the design of watercraft, aircraft, ventilation fans, and windmills.

Integrative and Comparative Biology

8024771

10.4161/PSB.4.9.9426

Biomechanics of climbing palms and how they climb

Climbing plants have fascinated botanists since the pioneering works of Darwin and his contemporaries in the 19th century. Diverse plants have evolved different ways of climbing and a wide range of attachment devices and stem biomechanics to cope with the particular physical demands of life as a climber. We investigated the biomechanics of attachment in a range of climbing palms, including true rattans from Southeast Asia and the genus Desmoncus from South America. We found that hook strength and orientation is coordinated with rachis geometry and rigidity. These findings support the notion of a ratchet-type attachment mechanism and partly explain why these spiny plants are so catchy and efficient at attaching to supports.

Plant Signaling & Behavior

84733920

10.4319/LO.1977.22.6.1067

Mechanical adaptations of a giant kelp

Unusually high extensibility of the kelp Nereocystis luetkeana minimizes breakage by waves and tidal currents. Cellulose fibrils in cortical cell walls have a preferred angle of 60° to the stipe axis; this may be the structural basis of stipe extensibility. Although undamaged plants can sustain drag due to most waves and tides, breakage of single plants occurs most often at flaws in the stipes caused by sea urchin grazing or by abrasion.

Limnology and Oceanography

86255591

10.1016/0022-0981(91)90254-T

Intertidal “trees”: consequences of aggregation on the mechanical and photosynthetic properties of sea-palms Postelsia palmaeformis Ruprecht

Sea-palms Postelsia palmaeformis Ruprecht are annual brown algae that grow on wave-swept rocky shores, oRen forming dense stands. Unlike most macroalgae, Postelsia stands upright in air- like trees. The stipe flexibility that permits Postelsia to withstand waves is provided by the low elastic modulus (5-10 MPa) of stipe tissue; in spite of the weakness (low breaking stress, ~ 1 MPa) of this tissue, a large amount of energy ( ~ 100 kJ/m 3) is required to break a stipe because they can be extended by 20-25 % before breaking. Although made of such easily deformed tissue, Postelsia can stand upright in air due to the width (high second moment of area) and resilience of their stipes, but the brittleness (low work of fracture, 400-900 J/m 2) that accompanies this resilience renders them susceptible to bre~age if they sustain deep scratches. Although wave-induced stresses experienced by individuals in aggregations are not lower than those experienced by isolated sea-palms, photon flux densities of photosynthetically active radiation within these dense groves are less than 10% of those above Postelsia canopies. A number of morphological features differ between canopy, understory, and isolated individuals. Canopy plants in dense aggregations are taller than isolated individuals and may exceed limiting proportions for elastic stability. Postelsia shows photo- synthetic characteristics of"shade-adapted" plants, understory individuals being especially effective at using low light. Despite this, blade growth rates of understory plants are lower than those of either canopy or isolated individuals.

Journal of Experimental Marine Biology and Ecology

46098494

10.1016/J.ANBEHAV.2015.09.004

Are chickadees good listeners? Antipredator responses to raptor vocalizations

Many animals gather information about predators with a variety of cues, such as visual, acoustic, and olfactory. Several species of birds, including chickadees, are good at discriminating between species of raptors using visual cues, and they can encode information about the threat level in their alarm calls. Much less is known about how birds discriminate between the calls of different species of predators. We played back the calls of three species of raptors to black-capped chickadees, Poecile atricapillus, mountain chickadees, Poecile gambeli, and chestnut-backed chickadees, Poecile rufescens, to determine whether they can discriminate between them using acoustic cues. We played the calls of two species of small, high-threat raptors, northern pygmy-owl, Glaucidium gnoma, and sharp-shinned hawk, Accipiter striatus, which have very different hunting strategies (mainly sit-and-wait ambush predator versus very fast surprise attack flights). We also played a larger, lower-threat northern goshawk, Accipiter gentilis. Black-capped and mountain chickadees responded much more to the calls of the two small, more dangerous raptors than to the northern goshawk; they also responded very differently to the calls of the two small raptors. Chestnut-backed chickadees did not respond differently to the calls of the three raptors. These results indicate that black-capped and mountain chickadees can make specific discriminations between the calls of these three raptors and that they encode information in their alarm calls in sophisticated ways.

Animal Behaviour

5877229

10.1126/SCIENCE.193.4252.484

Fog Catchment Sand Trenches Constructed by Tenebrionid Beetles, Lepidochora, from the Namib Desert

Three species of coastal Namib Desert tenebrionid beetles (Lepidochora) build trenches on desert sand dunes. Trenches are constructed perpendicular to fog winds and concentrate moisture during fogs. The beetles return along the ridges of the trenches extracting water from them. The water content of a population of these beetles increased by 13.9 percent during one fog

Science

53704972

10.1016/J.MSEC.2005.08.016

Mechanical properties and structure of Strombus gigas, Tridacna gigas, and Haliotis rufescens sea shells: A comparative study

Sea shells are composed of calcium carbonate crystals interleaved with layers of viscoelastic proteins, having dense, tailored structures that yield excellent mechanical properties. Shells such as conch (Strombus gigas), giant clam (Tridacna gigas), and red abalone (Haliotis rufescens) have hierarchical architectures that differ depending on growth requirements and shell formation of the particular mollusk. Mechanical tests have been carried out on these shells for a comparison of strength with respect to the microstructural architecture and sample orientation. The mechanical response is found to vary significantly from specimen to specimen and requires the application of Weibull statistics in order to be quantitatively evaluated. The complex micro-laminate structure of these biocomposite materials is characterized and related to their mechanical properties. The red abalone has the highest compressive (233–540 MPa) and flexure strengths of the three shells. The giant clam has the lowest strength (87–123 MPa) and the conch has an intermediate value (166–218 MPa) in compression. The high compressive strength observed in the abalone is attributed to an optimization of microstructural architecture in the form of 2-D laminates, enhancing the fracture toughness of this shell material and enabling higher stresses to develop before fracture. D 2005 Elsevier B.V. All rights reserved.

Materials Science and Engineering: C

25489871

10.1128/MMBR.63.4.735-750.1999

Alkaliphiles: Some Applications of Their Products for Biotechnology

SUMMARY The term “alkaliphile” is used for microorganisms that grow optimally or very well at pH values above 9 but cannot grow or grow only slowly at the near-neutral pH value of 6.5. Alkaliphiles include prokaryotes, eukaryotes, and archaea. Many different taxa are represented among the alkaliphiles, and some of these have been proposed as new taxa. Alkaliphiles can be isolated from normal environments such as garden soil, although viable counts of alkaliphiles are higher in samples from alkaline environments. The cell surface may play a key role in keeping the intracellular pH value in the range between 7 and 8.5, allowing alkaliphiles to thrive in alkaline environments, although adaptation mechanisms have not yet been clarified. Alkaliphiles have made a great impact in industrial applications. Biological detergents contain alkaline enzymes, such as alkaline cellulases and/or alkaline proteases, that have been produced from alkaliphiles. The current proportion of total world enzyme production destined for the laundry detergent market exceeds 60%. Another important application is the industrial production of cyclodextrin by alkaline cyclomaltodextrin glucanotransferase. This enzyme has reduced the production cost and paved the way for cyclodextrin use in large quantities in foodstuffs, chemicals, and pharmaceuticals. It has also been reported that alkali-treated wood pulp could be biologically bleached by xylanases produced by alkaliphiles. Other applications of various aspects of alkaliphiles are also discussed.

Microbiology and Molecular Biology Reviews

15178940

10.1007/S00418-011-0904-1

Epithelial sodium channels (ENaC) are uniformly distributed on motile cilia in the oviduct and the respiratory airways

Epithelial sodium channels (ENaCs) are located on the apical surface of cells and funnel Na+ ions from the lumen into the cell. ENaC function also regulates extracellular fluid volume as water flows across membranes accompanying Na+ ions to maintain osmolarity. To examine the sites of expression and intracellular localization of ENaC, we generated polyclonal antibodies against the extracellular domain of human α-ENaC subunit that we expressed in E. coli. Three-dimensional (3D) confocal microscopy of immunofluorescence using these antibodies for the first time revealed that ENaCs are uniformly distributed on the ciliary surface in all epithelial cells with motile cilia lining the bronchus in human lung and female reproductive tract, all along the fimbrial end of the fallopian tube, the ampulla and rare cells in the uterine glands. Quantitative analysis indicated that cilia increase cell surface area >70-fold and the amount of ENaC on cilia is >1,000-fold higher than on non-ciliated cell surface. These findings indicate that ENaC functions as a regulator of the osmolarity of the periciliary fluid bathing the cilia. In contrast to ENaC, cystic fibrosis transmembrane conductance regulator (CFTR) that channels chloride ions from the cytoplasm to the lumen is located mainly on the apical side, but not on cilia. The cilial localization of ENaC requires reevaluation of the mechanisms of action of CFTR and other modulators of ENaC function. ENaC on motile cilia should be essential for diverse functions of motile cilia, such as germ cell transport, fertilization, implantation, clearance of respiratory airways and cell migration.

Histochemistry and Cell Biology

54332729

10.1016/J.PHYSBEH.2006.04.024

Huddling behavior in emperor penguins: Dynamics of huddling

Although huddling was shown to be the key by which emperor penguins (Aptenodytes forsteri) save energy and sustain their breeding fast during the Antarctic winter, the intricacies of this social behavior have been poorly studied. We recorded abiotic variables with data loggers glued to the feathers of eight individually marked emperor penguins to investigate their thermoregulatory behavior and to estimate their "huddling time budget" throughout the breeding season (pairing and incubation period). Contrary to the classic view, huddling episodes were discontinuous and of short and variable duration, lasting 1.6+/-1.7 (S.D.) h on average. Despite heterogeneous huddling groups, birds had equal access to the warmth of the huddles. Throughout the breeding season, males huddled for 38+/-18% (S.D.) of their time, which raised the ambient temperature that birds were exposed to above 0 degrees C (at average external temperatures of -17 degrees C). As a consequence of tight huddles, ambient temperatures were above 20 degrees C during 13+/-12% (S.D.) of their huddling time. Ambient temperatures increased up to 37.5 degrees C, close to birds' body temperature. This complex social behavior therefore enables all breeders to get a regular and equal access to an environment which allows them to save energy and successfully incubate their eggs during the Antarctic winter.

Physiology & Behavior

1922782

10.1038/417241A

Neurology: An ancient sensory organ in crocodilians

Crocodilians hunt at night, waiting half-submerged for land-bound prey to disturb the water surface. Here I show that crocodilians have specialized sensory organs on their faces that can detect small disruptions in the surface of the surrounding water, and which are linked to a dedicated, hypertrophied nerve system. Such 'dome' pressure receptors are also evident in fossils from the Jurassic period, indicating that these semi-aquatic predators solved the problem of combining armour with tactile sensitivity many millions of years ago.

Nature

110895645

10.1098/RSPB.1999.0668

Evolution of the dragonfly head-arresting system

The arrester or fixation system of the head in adult Odonata is unique among arthropods. This system involves the organs of two body segments: the head and the neck. It consists of a skeleton–muscle apparatus that sets the arrester parts in motion. The parts comprise formations covered with complicated microstructures: fields of microtrichia on the rear surface of the head and post–cervical sclerites of the neck. The arrester immobilizes the head during feeding or when the dragonfly is in tandem flight. Thus, it may serve as an adaptation to save the head from violent mechanical disturbance and to stabilize gaze in a variety of behavioural situations. This study shows the evolutionary trend of the arrester in the order Odonata by using scanning electron microscopy and measurements of arrester structures in 227 species from 26 odonate families. The arrester design occurring in the Epiophlebiidae, Gomphidae, Neopetaliidae, Petaluridae and Chlorogomphinae is suggested to be the basic one. Two convergent pathways of head–arrester evolution among Zygoptera and Anisoptera are proposed. The possible functional significance of the arrester system is discussed.

Proceedings of The Royal Society B: Biological Sciences

6035407

10.1016/J.CUB.2010.06.074

Membrane Thickness Cue for Cold Sensing in a Bacterium

Thermosensors are ubiquitous integral membrane proteins found in all kinds of life. They are involved in many physiological roles, including membrane remodeling, chemotaxis, touch, and pain [1-3], but, the mechanism by which their transmembrane (TM) domains transmit temperature signals is largely unknown. The histidine kinase DesK from Bacillus subtilis is the paradigmatic example of a membrane-bound thermosensor suited to remodel membrane fluidity when the temperature drops below approximately 30°C [1, 4] providing, thus, a tractable system for investigating the mechanism of TM-mediated input-output control of thermal adaptation. Here we show that the multimembrane-spanning domain from DesK can be simplified into a chimerical single-membrane-spanning minimal sensor (MS) that fully retains, in vivo and in vitro, the sensing properties of the parental system. The MS N terminus contains three hydrophilic amino acids near the lipid-water interface creating an instability hot spot. Mutational analysis of this boundary-sensitive beacon revealed that membrane thickness controls the signaling state of the sensor by dictating the hydration level of the metastable hydrophilic spot. Guided by these results we biochemically demonstrated that the MS signal transmission activity is sensitive to bilayer thickness. Membrane thickness could be a general cue for sensing temperature in many organisms.

Current Biology

150248914

10.1016/J.CARBPOL.2019.04.059

Strong ultralight foams based on nanocrystalline cellulose for high-performance insulation.

Environmentally friendly, sustainable, and high-performance thermal insulators are in high demand. Petroleum-based insulator foams usually have high thermal conductivity and pose health hazards. Here, we report ultralight composite foams that are highly strong, elastic, and super-insulating. The foams are composed of nanocrystalline cellulose (NCC) (74 wt%), polyvinyl alcohol (7.5 wt%), and a crosslinking agent (18.5 wt%). The fabrication process is simple and uses only water. The composite foams exhibit an elastic strain of ˜13% at a modulus of 250 K Pa and a stress of 73 K Pa at 50% strain (100+ and 18 times, respectively, higher than those of pure NCC foam); both exceed the values of reported nanocellulose-based foams with no reinforcement. The foams exhibit a thermal conductivity of 0.027 Wm-1 K-1, which is superior to those of traditional insulating materials. The structural integrity is also preserved after burning. Our results show that NCC-based materials can be engineered towards high-performance insulation applications.

Carbohydrate Polymers

136855042

10.1016/J.MSEC.2007.12.001

Characterization of the nanocomposite laminate structure occurring in fish scales from Arapaima Gigas

In the present paper, the nanocomposite laminate structure of scales from the Amazonian fish Arapaima Gigas is investigated. The structure and composition of the scales were assessed by means of X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR). The theory of Fickian diffusion is used and discussed in order to rationalize the water absorption and desorption behavior of the scales. Morphology studies and fracture analysis of the native scales were carried out using Transmission Electron Microscopy (TEM), Light Optical Microscopy (LOM) and Scanning Electron Microscopy (SEM). A fibrous layer of collagen and a plywood-like structure were observed. In order to study the mineral phase, the native scales were burned at 600 °C until all the organic components were degraded. The remaining ashes were then observed under the microscope and weighed to determine ratio of organic and inorganic components. The mechanical behavior of dry and wet scales was assessed by tensile tests and the effect of water in mechanical properties is also discussed.

Materials Science and Engineering: C

35373524

10.1136/BJO.84.11.1214

From eye spots to eye shine

In the marginalia of Darwin's On the Origin of Species , the author's spouse wondered if, indeed, an eye could possibly “evolve” since it is so complex. Others, more recently, have asked the same question. Fortunately, similar doubt did not afflict Darwin. A review of the evolutionary evidence reveals ample evidence that eyes can and do evolve. For example, there are creatures that have multiple and very specific eyes, suggesting that eyes are not only rather easy to evolve, but, in some creatures, ocular evolution can be quite rapid. The process of organism photoreception probably started shortly after life began on this planet, stimulated by the sun. Ocular evolution responded to the sun's energy by producing phototaxis leading to crude eye spots, then ascending to the complex and elegant ocular structure of certain birds having two foveae and asymmetric lenses for precise focusing. Fantastic adaptations, often beyond imagination, have occurred and are with us today, including irregularly shaped eyes and special photopigments to view ultraviolet, infrared, and bioluminescence. The extension of the interpretation of electromagnetic waves into realms we cannot understand must create a fantastic panoply of colours and stimulations. And, yet, as ophthalmologists, we rarely consider that any visual system is significantly better than or even that different from our own. This is folly for many species have evolved spectacular and stunning adaptations to the visual imperatives of their world. The crepuscular aerial drama of a swallow on the wing hunting for a small erratic insect illustrates the profoundly complex visual processing necessary to provide identification, tracking, pursuit, and eventual capture in a dimly lit and almost clueless three dimensional environment. Yet, a swallow does this hundreds of times a day. Similarly, a bathypelagic piscine predator, living at a depth of 1500 metres, must face staggering problems merely identifying …

British Journal of Ophthalmology

2282611

10.1098/RSPB.2008.1860

Ants recognize foes and not friends

Discriminating among individuals and rejecting non-group members is essential for the evolution and stability of animal societies. Ants are good models for studying recognition mechanisms, because they are typically very efficient in discriminating ‘friends’ (nest-mates) from ‘foes’ (non-nest-mates). Recognition in ants involves multicomponent cues encoded in cuticular hydrocarbon profiles. Here, we tested whether workers of the carpenter ant Camponotus herculeanus use the presence and/or absence of cuticular hydrocarbons to discriminate between nest-mates and non-nest-mates. We supplemented the cuticular profile with synthetic hydrocarbons mixed to liquid food and then assessed behavioural responses using two different bioassays. Our results show that (i) the presence, but not the absence, of an additional hydrocarbon elicited aggression and that (ii) among the three classes of hydrocarbons tested (unbranched, mono-methylated and dimethylated alkanes; for mono-methylated alkanes, we present a new synthetic pathway), only the dimethylated alkane was effective in eliciting aggression. Our results suggest that carpenter ants use a fundamentally different mechanism for nest-mate recognition than previously thought. They do not specifically recognize nest-mates, but rather recognize and reject non-nest-mates bearing odour cues that are novel to their own colony cuticular hydrocarbon profile. This begs for a reappraisal of the mechanisms underlying recognition systems in social insects.

Proceedings of The Royal Society B: Biological Sciences

72335182

10.1016/J.CELL.2019.01.014

Pollen Cell Wall Patterns Form from Modulated Phases

The ornately geometric walls of pollen grains have inspired scientists for decades. We show that the evolved diversity of these patterns is entirely recapitulated by a biophysical model in which an initially uniform polysaccharide layer in the extracellular space, mechanically coupled to the cell membrane, phase separates to a spatially modulated state. Experiments reveal this process occurring in living cells. We observe that in ∼10% of extant species, this phase separation reaches equilibrium during development such that individual pollen grains are identical and perfectly reproducible. About 90% of species undergo an arrest of this process prior to equilibrium such that individual grains are similar but inexact copies. Equilibrium patterns have appeared multiple times during the evolution of seed plants, but selection does not favor these states. This framework for pattern development provides a route to rationalizing the surface textures of other secreted structures, such as cell walls and insect cuticle.

Cell

1461255

10.1126/SCIENCE.289.5486.1902

Bacterial rhodopsin: evidence for a new type of phototrophy in the sea.

Extremely halophilic archaea contain retinal-binding integral membrane proteins called bacteriorhodopsins that function as light-driven proton pumps. So far, bacteriorhodopsins capable of generating a chemiosmotic membrane potential in response to light have been demonstrated only in halophilic archaea. We describe here a type of rhodopsin derived from bacteria that was discovered through genomic analyses of naturally occuring marine bacterioplankton. The bacterial rhodopsin was encoded in the genome of an uncultivated gamma-proteobacterium and shared highest amino acid sequence similarity with archaeal rhodopsins. The protein was functionally expressed in Escherichia coli and bound retinal to form an active, light-driven proton pump. The new rhodopsin exhibited a photochemical reaction cycle with intermediates and kinetics characteristic of archaeal proton-pumping rhodopsins. Our results demonstrate that archaeal-like rhodopsins are broadly distributed among different taxa, including members of the domain Bacteria. Our data also indicate that a previously unsuspected mode of bacterially mediated light-driven energy generation may commonly occur in oceanic surface waters worldwide.

Science

44637968

10.1016/J.TREE.2005.11.015

Regional and global concerns over wetlands and water quality.

Water quality in many stream catchments and river basins is severely impacted by nutrient enrichment as a result of agriculture. Water-resource managers worldwide are considering the potential role of riparian zones and floodplain wetlands in improving stream-water quality, as there is evidence at the site scale that such wetlands are efficient at removing nutrients from through-flowing water. However, recent studies have highlighted disadvantages of such use of wetlands, including emissions of greenhouse gases and losses of biodiversity that result from prolonged nutrient loading. Here, we discuss the water purification function of wetlands at the site and catchment scale and suggest ways in which these disadvantages could be overcome.

Trends in Ecology and Evolution

59028629

10.1139/Z01-192

Sticking ability in Spix's disk-winged bat, Thyroptera tricolor (Microchiroptera: Thyropteridae)

Roosting Spix's disk-winged bats, Thyroptera tricolor, use disks on their wrists and ankles to cling to smooth leaves. In 584 trials we tested the ability of 31 T. tricolor and 121 other bats lacking disks (461 trials with 18 species from three families) to adhere to (i) medium-grade sandpaper, (ii) Lexan polycarbonate, (iii) solid sheet aluminum, and (iv) porous sheet aluminum. While T. tricolor readily adhered to smooth surfaces, the other species did not. Thyroptera tricolor did not show the same ability to adhere to rough surfaces as the other species that were tested. As was demonstrated by their performance on porous aluminum and sandpaper, the disks of T. tricolor worked by suction and sometimes by wet adhesion. In the course of adapting to adhere to smooth surfaces, T. tricolor appear to have lost some ability to roost on rough ones, although one adult T. tricolor climbed on a screen covering the inside walls of the polycarbonate cage by interlocking its thumb claws with the surface.

Canadian Journal of Zoology

136952669

10.1016/S1672-6529(07)60008-0

Study of the geometry and folding pattern of leaves of Mimosa pudica

Many structural and functional properties possessed by plants have great potentials to stimulate new concepts and innovative ideas in the field of biomimetic engineering. The key inputs from biology can be used for creation of efficient and optimized structures. The study of the geometry and folding pattern of leaves of Mimosa pudica, referred as Sensitive Plant, reveals some of the peculiar characteristics during folding and unfolding. When the leaf is touched, it quickly folds its leaflets and pinnae and droops downward at the petiole attachment. With the help of experiments on simulation model, the variations in angle of leaflets and degree of compaction after folding are investigated.

Journal of Bionic Engineering

15816725

10.1146/ANNUREV.ENTO.42.1.587

Biology of Wolbachia.

Wolbachia are a common and widespread group of bacteria found in reproductive tissues of arthropods. These bacteria are transmitted through the cytoplasm of eggs and have evolved various mechanisms for manipulating reproduction of their hosts, including induction of reproductive incompatibility, parthenogenesis, and feminization. Wolbachia are also transmitted horizontally between arthropod species. Significant recent advances have been made in the study of these interesting microorganisms. In this paper, Wolbachia biology is reviewed, including their phylogeny and distribution, mechanisms of action, population biology and evolution, and biological control implications. Potential directions for future research are also discussed.

Annual Review of Entomology

86902232

10.2307/1366197

TRANSPORT OF WATER BY ADULT SANDGROUSE TO THEIR YOUNG

The Condor

85339536

10.1017/S0025315400037826

Bioluminescence in the benthopelagic holothurian Enypniastes eximia

Enypniastes eximia (Echinodermata: Holothuroidea) is a prominent member of the benthic boundary layer community in deep Caribbean waters. Like most holothurians it feeds on benthic sediments. Feeding is episodic and after collecting food on the bottom it returns to the water column at altitudes within about 50 m of the sea floor. Direct observations from submersibles and laboratory studies of living specimens have shown how bioluminescence is produced. Light production in E. eximia is triggered mechanically, and is produced by hundreds of granular bodies within the gelatinous integument of the animal. Local stimulation yields a localized response which gradually spreads to the entire surface of the animal. Broad impact yields a whole-body luminescent response. The integument of E. eximia is quite fragile, and strong physical contact readily causes the skin to be sloughed off in a glowing cloud. The degree of luminous response is a function of the severity of contact. In the laboratory the skin of E. eximia , along with its luminescent capability, regenerated rapidly. The anti-predatory role of bioluminescence in this species is apparently a ‘burglar alarm’ strategy. In the dark, near-bottom habitat, physical contact by a predator elicits light production which reveals the presence of the attacker to its own visually-cued predators.

Journal of the Marine Biological Association of the United Kingdom

32034417

10.1146/ANNUREV.IMMUNOL.17.1.593

Mechanisms of phagocytosis in macrophages.

Phagocytosis of pathogens by macrophages initiates the innate immune response, which in turn orchestrates the adaptive response. In order to discriminate between infectious agents and self, macrophages have evolved a restricted number of phagocytic receptors, like the mannose receptor, that recognize conserved motifs on pathogens. Pathogens are also phagocytosed by complement receptors after relatively nonspecific opsonization with complement and by Fc receptors after specific opsonization with antibodies. All these receptors induce rearrangements in the actin cytoskeleton that lead to the internalization of the particle. However, important differences in the molecular mechanisms underlying phagocytosis by different receptors are now being appreciated. These include differences in the cytoskeletal elements that mediate ingestion, differences in vacuole maturation, and differences in inflammatory responses. Infectious agents, such as M. tuberculosis, Legionella pneumophila, and Salmonella typhimurium, enter macrophages via heterogeneous pathways and modify vacuolar maturation in a manner that favors their survival. Macrophages also play an important role in the recognition and clearance of apoptotic cells; a notable feature of this process is the absence of an inflammatory response.

Annual Review of Immunology

16188807

10.1016/J.JSB.2011.08.006

Selectivity in biomineralization of barium and strontium.

The desmid green alga Closterium moniliferum belongs to a small number of organisms that form barite (BaSO(4)) or celestite (SrSO(4)) biominerals. The ability to sequester Sr in the presence of an excess of Ca is of considerable interest for the remediation of (90)Sr from the environment and nuclear waste. While most cells dynamically regulate the concentration of the second messenger Ca(2+) in the cytosol and various organelles, transport proteins rarely discriminate strongly between Ca, Sr, and Ba. Herein, we investigate how these ions are trafficked in C. moniliferum and how precipitation of (Ba,Sr)SO(4) crystals occurs in the terminal vacuoles. Towards this goal, we simultaneously visualize intracellular dynamics of multiple elements using X-ray fluorescence microscopy (XFM) of cryo-fixed/freeze-dried samples. We correlate the resulting elemental maps with ultrastructural information gleaned from freeze-fracture cryo-SEM of frozen-hydrated cells and use micro X-ray absorption near edge structure (micro-XANES) to determine sulfur speciation. We find that the kinetics of Sr uptake and efflux depend on external Ca concentrations, and Sr, Ba, and Ca show similar intracellular localization. A highly ion-selective cross-membrane transport step is not evident. Based on elevated levels of sulfate detected in the terminal vacuoles, we propose a "sulfate trap" model, where the presence of dissolved barium leads to preferential precipitation of (Ba,Sr)SO(4) due to its low solubility relative to SrSO(4) and CaSO(4). Engineering the sulfate concentration in the vacuole may thus be the most direct way to increase the Sr sequestered per cell, an important consideration in using desmids for phytoremediation of (90)Sr.

Journal of Structural Biology

14637221

10.1128/EC.00064-07

Proposed Carbon Dioxide Concentrating Mechanism in Chlamydomonas reinhardtii

Aquatic photosynthetic microorganisms account for almost 50% of the world's photosynthesis ([19][1]). These organisms face several challenges in acquiring CO2 from the environment. The first challenge is presented by the properties of ribulose bisphosphate carboxylase-oxygenase (Rubisco). Rubisco is

Eukaryotic Cell

221657180

10.3759/TROPICS.7.93

ニューギニアの着生性アリ植物 Hydnophytum moseleyanum より見出された多様な動物相

Tropics

10275213

10.3389/FNANA.2010.00027

A Comparative Study of Age-Related Hearing Loss in Wild Type and Insulin-Like Growth Factor I Deficient Mice

Insulin-like growth factor-I (IGF-I) belongs to the family of insulin-related peptides that fulfils a key role during the late development of the nervous system. Human IGF1 mutations cause profound deafness, poor growth and mental retardation. Accordingly, Igf1−/− null mice are dwarfs that have low survival rates, cochlear alterations and severe sensorineural deafness. Presbycusis (age-related hearing loss) is a common disorder associated with aging that causes social and cognitive problems. Aging is also associated with a decrease in circulating IGF-I levels and this reduction has been related to cognitive and brain alterations, although there is no information as yet regarding the relationship between presbycusis and IGF-I biodisponibility. Here we present a longitudinal study of wild type Igf1+/+ and null Igf1−/− mice from 2 to 12 months of age comparing the temporal progression of several parameters: hearing, brain morphology, cochlear cytoarchitecture, insulin-related factors and IGF gene expression and IGF-I serum levels. Complementary invasive and non-invasive techniques were used, including auditory brainstem-evoked response (ABR) recordings and in vivo MRI brain imaging. Igf1−/− null mice presented profound deafness at all the ages studied, without any obvious worsening of hearing parameters with aging. Igf1+/+ wild type mice suffered significant age-related hearing loss, their auditory thresholds and peak I latencies augmenting as they aged, in parallel with a decrease in the circulating levels of IGF-I. Accordingly, there was an age-related spiral ganglion degeneration in wild type mice that was not evident in the Igf1 null mice. However, the Igf1−/− null mice in turn developed a prematurely aged stria vascularis reminiscent of the diabetic strial phenotype. Our data indicate that IGF-I is required for the correct development and maintenance of hearing, supporting the idea that IGF-I-based therapies could contribute to prevent or ameliorate age-related hearing loss.

Frontiers in Neuroanatomy

83565702

10.2307/1938550

Surface Temperatures of Cacti‐‐Influences of Environmental and Morphological Factors

An energy budget model predicted the average stem surface temperatures of a Mam- millaria dioica 9.4 cm tail and a Carnegiea gigantea 5.64 m tail within 1?C of the hourly measured temperatures over 24-h periods. For the ranges of various environmental factors considered in a sensitivity analysis, the average surface temperature of the stem was most influenced by air temper? ature. Greater diurnal extremes of stem temperature occurred at lower wind velocities. Asymmetrical heating of the stem by direct solar irradiation was clearly evident in the measurements and the simulations. The model was used to study the effect of changes in spine coverage, apical pubescence, stem absorptance, tissue thermal properties, plant height, and diameter on stem surface temperatures. In the absence of spines the average surface temperature of Mammillaria became 1 to 2?C cooler at night and 2 to 6?C warmer during the day. The effect of spines on the simulated diurnal temperature variation was even greater for the apical meristem, which had the most dense coverage of spines. A mat of pubescence additionally protected the apical meristem of Carnegiea and Ferocactus acan- thodes, substantially reducing diurnal temperature extremes there. Simulated decreases in the di? ameter of Carnegiea increased the daily range of temperatures of the apical meristem, suggesting that some adaptive optimization of plant diameter may have occurred. Simulations for the 3 species under the same environmental conditions showed that the lowest stem and apical temperatures occurred for Carnegiea, consistent with its restriction to lower (presumably warmer) elevations than Ferocactus and Mammillaria.

Ecology

6694070

10.1098/RSIF.2009.0308

Insect tricks: two-phasic foot pad secretion prevents slipping

Many insects cling to vertical and inverted surfaces with pads that adhere by nanometre-thin films of liquid secretion. This fluid is an emulsion, consisting of watery droplets in an oily continuous phase. The detailed function of its two-phasic nature has remained unclear. Here we show that the pad emulsion provides a mechanism that prevents insects from slipping on smooth substrates. We discovered that it is possible to manipulate the adhesive secretion in vivo using smooth polyimide substrates that selectively absorb its watery component. While thick layers of polyimide spin-coated onto glass removed all visible hydrophilic droplets, thin coatings left the emulsion in its typical form. Force measurements of stick insect pads sliding on these substrates demonstrated that the reduction of the watery phase resulted in a significant decrease in friction forces. Artificial control pads made of polydimethylsiloxane showed no difference when tested on the same substrates, confirming that the effect is caused by the insects’ fluid-based adhesive system. Our findings suggest that insect adhesive pads use emulsions with non-Newtonian properties, which may have been optimized by natural selection. Emulsions as adhesive secretions combine the benefits of ‘wet’ adhesion and resistance against shear forces.

Journal of the Royal Society Interface

14188921

10.1371/JOURNAL.PBIO.0060059

A Role for Parasites in Stabilising the Fig-Pollinator Mutualism

Mutualisms are interspecific interactions in which both players benefit. Explaining their maintenance is problematic, because cheaters should outcompete cooperative conspecifics, leading to mutualism instability. Monoecious figs (Ficus) are pollinated by host-specific wasps (Agaonidae), whose larvae gall ovules in their “fruits” (syconia). Female pollinating wasps oviposit directly into Ficus ovules from inside the receptive syconium. Across Ficus species, there is a widely documented segregation of pollinator galls in inner ovules and seeds in outer ovules. This pattern suggests that wasps avoid, or are prevented from ovipositing into, outer ovules, and this results in mutualism stability. However, the mechanisms preventing wasps from exploiting outer ovules remain unknown. We report that in Ficus rubiginosa, offspring in outer ovules are vulnerable to attack by parasitic wasps that oviposit from outside the syconium. Parasitism risk decreases towards the centre of the syconium, where inner ovules provide enemy-free space for pollinator offspring. We suggest that the resulting gradient in offspring viability is likely to contribute to selection on pollinators to avoid outer ovules, and by forcing wasps to focus on a subset of ovules, reduces their galling rates. This previously unidentified mechanism may therefore contribute to mutualism persistence independent of additional factors that invoke plant defences against pollinator oviposition, or physiological constraints on pollinators that prevent oviposition in all available ovules.

PLOS Biology

1052730

10.1098/RSPB.2012.0558

Dermal bone in early tetrapods: a palaeophysiological hypothesis of adaptation for terrestrial acidosis

The dermal bone sculpture of early, basal tetrapods of the Permo-Carboniferous is unlike the bone surface of any living vertebrate, and its function has long been obscure. Drawing from physiological studies of extant tetrapods, where dermal bone or other calcified tissues aid in regulating acid–base balance relating to hypercapnia (excess blood carbon dioxide) and/or lactate acidosis, we propose a similar function for these sculptured dermal bones in early tetrapods. Unlike the condition in modern reptiles, which experience hypercapnia when submerged in water, these animals would have experienced hypercapnia on land, owing to likely inefficient means of eliminating carbon dioxide. The different patterns of dermal bone sculpture in these tetrapods largely correlates with levels of terrestriality: sculpture is reduced or lost in stem amniotes that likely had the more efficient lung ventilation mode of costal aspiration, and in small-sized stem amphibians that would have been able to use the skin for gas exchange.

Proceedings of The Royal Society B: Biological Sciences

211089119

10.1038/S41586-020-1990-9

Evolution-guided discovery of antibiotics that inhibit peptidoglycan remodelling

Addressing the ongoing antibiotic crisis requires the discovery of compounds with novel mechanisms of action that are capable of treating drug-resistant infections 1 . Many antibiotics are sourced from specialized metabolites produced by bacteria, particularly those of the Actinomycetes family 2 . Although actinomycete extracts have traditionally been screened using activity-based platforms, this approach has become unfavourable owing to the frequent rediscovery of known compounds. Genome sequencing of actinomycetes reveals an untapped reservoir of biosynthetic gene clusters, but prioritization is required to predict which gene clusters may yield promising new chemical matter 2 . Here we make use of the phylogeny of biosynthetic genes along with the lack of known resistance determinants to predict divergent members of the glycopeptide family of antibiotics that are likely to possess new biological activities. Using these predictions, we uncovered two members of a new functional class of glycopeptide antibiotics—the known glycopeptide antibiotic complestatin and a newly discovered compound we call corbomycin—that have a novel mode of action. We show that by binding to peptidoglycan, complestatin and corbomycin block the action of autolysins—essential peptidoglycan hydrolases that are required for remodelling of the cell wall during growth. Corbomycin and complestatin have low levels of resistance development and are effective in reducing bacterial burden in a mouse model of skin MRSA infection. The glycopeptide antibiotic-related compounds complestatin and corbomycin function by binding to peptidoglycan and blocking the action of autolysins—peptidoglycan hydrolase enzymes that remodel the cell wall during growth.

Nature

85186972

10.1111/J.1096-3642.2000.TB02198.X

Incidence and mechanical significance of pneumatization in the long bones of birds

The incidence of pneumatization in avian long bones was studied, by direct observation, in a large sample of species. Only proximal bones (humerus and femur) presented pneumatization in the sample studied. The incidence obtained was related to the variation of the maximum cortical thickness and mechanical properties, such as bending strength and flexural Young's modulus. Cortical thickness, bending strength and flexural Young's modulus were significantly lower in pneumatized bones than in marrow-filled bones. Furthermore, some congruence was found between pneumatization and systematic groups when compared. In this sense, Charadriformes was the only order studied with total absence of long bone pneumatization. Results on cortical thickness appear to be in agreement with modelling predictions previously made and with results obtained on other groups of flying vertebrates. The possible selective advantage of reduction in cortical thickness in relation to flying is suggested.

Zoological Journal of the Linnean Society

7308257

10.1529/BIOPHYSJ.106.089144

Design of superior spider silk: from nanostructure to mechanical properties.

Spider dragline silk is of practical interest because of its excellent mechanical properties. However, the structure of this material is still largely unknown. In this article, we report what we believe is a new model of the hierarchical structure of silk based on scanning electron microscope and atomic force microscope images. This hierarchical structure includes beta-sheet, polypeptide chain network, and silk fibril. It turns out that an exceptionally high strength of the spider dragline silk can be obtained by decreasing the size of the crystalline nodes in the polypeptide chain network while increasing the degree of orientation of the crystalline nodes. Based on this understanding, how the reeling speed affects mechanical properties of spider dragline silk can be understood properly. Hopefully, the understanding obtained in this study will shed light on the formation of spider silk, and consequently, on the principles for the design of ultrastrong silk.

Biophysical Journal

205606621

10.1111/J.1469-8137.2009.03166.X

Trap geometry in three giant montane pitcher plant species from Borneo is a function of tree shrew body size.

*Three Bornean pitcher plant species, Nepenthes lowii, N. rajah and N. macrophylla, produce modified pitchers that 'capture' tree shrew faeces for nutritional benefit. Tree shrews (Tupaia montana) feed on exudates produced by glands on the inner surfaces of the pitcher lids and defecate into the pitchers. *Here, we tested the hypothesis that pitcher geometry in these species is related to tree shrew body size by comparing the pitcher characteristics with those of five other 'typical' (arthropod-trapping) Nepenthes species. *We found that only pitchers with large orifices and lids that are concave, elongated and oriented approximately at right angles to the orifice capture faeces. The distance from the tree shrews' food source (that is, the lid nectar glands) to the front of the pitcher orifice precisely matches the head plus body length of T. montana in the faeces-trapping species, and is a function of orifice size and the angle of lid reflexion. *Substantial changes to nutrient acquisition strategies in carnivorous plants may occur through simple modifications to trap geometry. This extraordinary plant-animal interaction adds to a growing body of evidence that Nepenthes represents a candidate model for adaptive radiation with regard to nitrogen sequestration strategies.

New Phytologist

40331169

10.1038/NCHEMBIO0907-537

Cleaving C-Hg bonds: two thiolates are better than one

Organomercurial lyase (MerB) catalyzes the difficult cleavage of C-Hg bonds to hydrocarbon and mercuric dithiol products. Model compounds providing two or three thiolate ligands activate organomercurials toward acidic cleavage under mild conditions, which supports a mechanism in which MerB enzymes use two conserved active-site cysteines to activate the substrate.

Nature Chemical Biology

96726950

10.1021/AR00072A003

Artificial photosynthesis: water cleavage into hydrogen and oxygen by visible light

Accounts of Chemical Research

2575554

10.1146/ANNUREV.MICRO.60.080805.142053

Arsenic and selenium in microbial metabolism.

Arsenic and selenium are readily metabolized by prokaryotes, participating in a full range of metabolic functions including assimilation, methylation, detoxification, and anaerobic respiration. Arsenic speciation and mobility is affected by microbes through oxidation/reduction reactions as part of resistance and respiratory processes. A robust arsenic cycle has been demonstrated in diverse environments. Respiratory arsenate reductases, arsenic methyltransferases, and new components in arsenic resistance have been recently described. The requirement for selenium stems primarily from its incorporation into selenocysteine and its function in selenoenzymes. Selenium oxyanions can serve as an electron acceptor in anaerobic respiration, forming distinct nanoparticles of elemental selenium that may be enriched in (76)Se. The biogenesis of selenoproteins has been elucidated, and selenium methyltransferases and a respiratory selenate reductase have also been described. This review highlights recent advances in ecology, biochemistry, and molecular biology and provides a prelude to the impact of genomics studies.

Annual Review of Microbiology

9267515

10.1007/BF00328814

Leaf dynamics, self-shading and carbon gain in seedlings of a tropical pioneer tree

We examined leaf dynamics and leaf age gradients of photosynthetic capacity and nitrogen concentration in seedlings of the tropical pioneer tree, Heliocarpus appendiculatus, grown in a factorial design under controlled conditions with two levels each of nutrients, ambient light (light levels incident above the canopy), and self-shading (the gradient of light levels from upper to lower leaves on the shoot). Correlations among these parameters were examined in order to determine the influence of self-shading, and the regulation of standing leaf numbers, on leaf longevity and its association with leaf photosynthetic capacity. Leaf longevity and the number of leaves on the main shoot were both reduced in high light, while in the low light environment, they were reduced in the steeper self-shading gradient. In high nutrients, leaf longevity was reduced whereas leaf number increased. Leaf initiation rates were higher in the high nutrient treatment but were not influenced by either light treatment. Maximum-light saturated photosynthetic rate, on an area basis, was greater in the high light and nutrient treatments, while the decline in photosynthetic capacity in realtion to leaf position on the shoot was more rapid in high light and in low nutrients. Leaf longevity was negatively correlated among treatments with initial photosynthetic capacity. The leaf position at which photosynthetic capacity was predicted to reach zero was positively correlated with the number of leaves on the shoot, supporting the hypothesis that leaf numbers are regulated by patterns of self-shading. The negative association of longevity and initial photosynthetic capacity apparently arises from different associations among gradients of photosynthetic capacity, leaf numbers and leaf initiation rates in relation to light and nutrient availability. The simultaneous consideration of age and position of leaves illuminates the role of self-shading as an important factor influencing leaf senescence and canopy structure and dynamics.

Oecologia

1688247

10.1126/SCIENCE.1067797

Bile Acid Secreted by Male Sea Lamprey That Acts as a Sex Pheromone

We show that reproductively mature male sea lampreys release a bile acid that acts as a potent sex pheromone, inducing preference and searching behavior in ovulated female lampreys. The secreted bile acid 7α,12α,24-trihydroxy-5α-cholan-3-one 24-sulfate was released in much higher amounts relative to known vertebrate steroid pheromones and may be secreted through the gills. Hence, the male of this fish species signals both its reproductive status and location to females by secreting a pheromone that can act over long distances.

Science

40235608

10.1017/S0033583506004458

The structure of aquaporins

1. Introduction 362 1.1 The elusive water pores 362 1.2 CHIP28 362 2. Studies on AQP-1 363 2.1 Expression of AQP1 cDNA in Xenopus oocytes 363 2.2 Reconstitution of purified AQP1 into artificial lipid bilayers 364 2.3 Structural information deduced from the primary sequence 365 2.4 Evolution and mammalian AQPs 365 3. Chronological overview over AQP structures 368 3.1 AQP1 – the red blood cell water pore 368 3.2 GlpF – the E. coli glycerol facilitator 371 3.3 AQPZ – the E. coli water pore 372 3.4 AQP0 – the lens-specific aquaporin 373 3.5 AQP4 – the main aquaporin in brain 377 3.6 SoPiP2;1 – a plant aquaporin 379 3.7 AQPM – an archaeabacterial aquaporin 379 4. Proton exclusion 380 5. Substrate selectivity 382 6. Pore regulation 385 6.1 Hormonal regulation of AQP trafficking 385 6.2 Influence of pH on AQP water conduction 386 6.3 Regulation of AQP pore conductance by protein binding 387 6.4 Pore closure by conformational changes in the AQP0 pore 388 7. Unresolved questions 390 8. Acknowledgments 390 9. References 391 The ubiquitous members of the aquaporin (AQP) family form transmembrane pores that are either exclusive for water (aquaporins) or are also permeable for other small neutral solutes such as glycerol (aquaglyceroporins). The purpose of this review is to provide an overview of our current knowledge of AQP structures and to describe the structural features that define the function of these membrane pores. The review will discuss the mechanisms governing water conduction, proton exclusion and substrate specificity, and how the pore permeability is regulated in different members of the AQP family.

Quarterly Reviews of Biophysics

3167149

10.4319/LO.2003.48.2.0795

Sea urchin spawning in benthic boundary layers: Are eggs fertilized before advecting away from females?

Past work on fertilization in echinoids and other egg-broadcasting, free-spawning invertebrates suggests that these organisms might be extremely sperm limited in the field unless individuals spawn in close proximity and under nearly ideal flow conditions. However, virtually all previous experiments have used one or more techniques (surrogates for males and females, and short sampling duration) that bypassed two potentially important aspects of echinoid reproductive biology: the release of gametes in viscous fluids that cling to tests and spines, and extended longevity of eggs and undiluted sperm. We hypothesized that these attributes might interact with some flow regimes to facilitate time-integrated fertilization. Consequently, we explored fertilization processes in sea urchins induced to spawn in a benthic boundary layer in a flow-through flume, with a male 0.5 m upstream of a female. Our observations and data suggest that at free‐stream flow velocities of 2.5 and 8.5 cm s 21 , gametes were slowly and continually advected from the aboral surfaces of spawning animals. Eggs on the surface of the aboral mass were often fertilized before they ablated from the surface; many advected eggs were fertilized after being trapped in the vortex downstream of the female. Gamete advection and fertilization continued for several hours, with the actual time course depending on flow velocity. Fertilization levels declined only slightly with increasing flow velocity. These results suggest that fertilization in echinoderms and other free-spawners with viscous, long-lived gametes could be much less sperm-limited than currently envisioned and have additional implications for population dynamics and selection on gamete characteristics.

Limnology and Oceanography

59404890

10.2307/1447748

Acclimation or Innate Protection of Anemonefishes from Sea Anemones

Studies have shown that anemonefishes can acquire protection from the stinging tentacles of their host anemones through a behavioral process called "acclimation." However, some investigators have suggested that anemonefishes are innately protected from all species of host anemones. To definitively test whether anemonefishes are innately protected from anemones, we forced "naive" anemonefishes, bred and raised in complete isolation from anemones, to contact the tentacles of Macrodactyla doreensis, Heteractis crispa, and Stichodactyla haddoni. Individuals of Amphiprion clarkii were protected when forced to contact the tentacles of all three anemone species. However, individuals of A. ocellaris and A. perideraion were stung by some anemones. All fishes went through acclimation behavior after the initial forced contact with anemones. Thus, anemonefishes are innately protected from some anemone species but must acclimate to live with others.

Copeia

137181141

10.1080/00218460902782279

In Situ Imaging of Barnacle (Balanus amphitrite) Cyprid Cement Using Confocal Raman Microscopy

Barnacles are a model for research on permanent underwater adhesion and the wider process of marine biofouling. A detailed understanding of the permanent adhesive secreted by the cypris larva for permanent settlement, the so-called cyprid cement, has potential to lead to novel antifouling solutions. There is a need for micro-analytical chemical in situ methods to gain more insight into the process of adhesion and the chemical composition of the cement. In this study, the applicability of confocal Raman microscopy for imaging the cyprid cement beneath permanently attached juvenile barnacles (Balanus amphitrite) was explored. Based on acquired area scans Raman images for characteristic chemical functional groups were obtained. In addition to showing the morphology of the attachment apparatus, the images provided information on chemical composition, in particular the hydration state of the cement, and demonstrated the potential of this method for in situ studies of adhesion at the micro-scale.

Journal of Adhesion

6080571

10.1242/JEB.070268

Avoidance and tolerance of freezing in ectothermic vertebrates

Summary Ectothermic vertebrates have colonized regions that are seasonally or perpetually cold, and some species, particularly terrestrial hibernators, must cope with temperatures that fall substantially below 0°C. Survival of such excursions depends on either freeze avoidance through supercooling or freeze tolerance. Supercooling, a metastable state in which body fluids remain liquid below the equilibrium freezing/melting point, is promoted by physiological responses that protect against chilling injury and by anatomical and behavioral traits that limit risk of inoculative freezing by environmental ice and ice-nucleating agents. Freeze tolerance evolved from responses to fundamental stresses to permit survival of the freezing of a substantial amount of body water under thermal and temporal conditions of ecological relevance. Survival of freezing is promoted by a complex suite of molecular, biochemical and physiological responses that limit cell death from excessive shrinkage, damage to macromolecules and membranes, metabolic perturbation and oxidative stress. Although freeze avoidance and freeze tolerance generally are mutually exclusive strategies, a few species can switch between them, the mode used in a particular instance of chilling depending on prevailing physiological and environmental conditions.

The Journal of Experimental Biology

10224540

10.1016/S1095-6433(02)00143-5

Tendon elasticity and muscle function.

Vertebrate animals exploit the elastic properties of their tendons in several different ways. Firstly, metabolic energy can be saved in locomotion if tendons stretch and then recoil, storing and returning elastic strain energy, as the animal loses and regains kinetic energy. Leg tendons save energy in this way when birds and mammals run, and an aponeurosis in the back is also important in galloping mammals. Tendons may have similar energy-saving roles in other modes of locomotion, for example in cetacean swimming. Secondly, tendons can recoil elastically much faster than muscles can shorten, enabling animals to jump further than they otherwise could. Thirdly, tendon elasticity affects the control of muscles, enhancing force control at the expense of position control.

Comparative Biochemistry and Physiology A-molecular & Integrative Physiology

6744760

10.1146/ANNUREV.ECOLSYS.27.1.365

NATURAL FREEZING SURVIVAL IN ANIMALS

Natural freeze-tolerance supports the winter survival of many animals including numerous terrestrial insects, many intertidal marine invertebrates, and selected species of terrestrially hibernating amphibians and reptiles. Freeze-tolerant animals typically endure the conversion of 50% or more of total body water into extracellular ice and employ a suite of adaptations that counter the negative consequences of freezing. Specific adaptations control the sites and rate of ice formation to prevent physical damage by ice. Other adaptations regulate cell-volume change: Colligative cryoprotectants minimize cell shrinkage during extracellular ice formation; other protectants stabilize membrane structure; and a high density of membrane transporter proteins ensure rapid cryoprotectant distribution. Cell survival during freezing is also potentiated by anoxia tolerance, mechanisms of metabolic rate depression, and antioxidant defenses. The net result of these protective mechanisms is the ability to reactivate vital functions after days or weeks of continuous freezing. Magnetic resonance imaging has allowed visual examinations of the mode of ice penetration through the body of freeze-tolerant frogs and turtles, and cryomicroscopy has illustrated the effects of freezing on the cellular and microvasculature structure of tissues. Various metabolic adaptations for freezing survival appear to have evolved out of pre-existing physiological capacities of animals, including desiccation-resistance and anoxia-tolerance.

Annual Review of Ecology, Evolution, and Systematics

16616906

10.4319/LO.2006.51.3.1485

Spawning events in small and large populations of the green sea urchin Strongylocentrotus droebachiensis as recorded using fertilization assays

During the winter and spring of 2002 and 2003, we used time-integrated fertilization assays to monitor sperm availability in three populations of the green sea urchin Strongylocentrotus droebachiensis in Maine: a naturally occurring population of >40,000 urchins and two smaller groups (<1,000) of transplanted urchins isolated from other aggregations. Episodes of sperm release coincided in two populations 10 km apart, suggesting that urchins were responding to a widespread environmental signal. We observed significant lunar periodicity in sperm release events for both of these populations. However, extensive spawning as shown by fertilization rates near 100% and a dramatic drop in gonad mass only occurred in the large natural population around the onset of thermal stratification and the spring phytoplankton bloom. By contrast, in the two small populations we observed low fertilization rates and little or no change in gonad mass. We speculate that a subset of males in these populations responded to a common external spawning signal, but that mass spawning is more likely to occur in large, dense populations where sperm concentrations reach high enough levels to trigger spawning in less responsive urchins.

Limnology and Oceanography

16337987

10.1093/JXB/ERF109

Partial purification of tomato fruit peroxidase and its effect on the mechanical properties of tomato fruit skin.

Peroxidase (EC 1.11.1.7)-mediated stiffening of cell walls within the fruit skin of tomato is hypothesized to regulate fruit growth. However, to date, there is no experimental evidence demonstrating that peroxidase affects the mechanical properties of skin tissue. Here, the mechanical properties of skin strips excised from a range of fruits at different ages were determined using an 'Instron' universal material testing instrument. The stiffness of tomato fruit skin strips increases 3-fold with increasing fruit age. Application of partially-purified peroxidase from the cell walls of mature tomato fruit skin significantly increased the stiffness of fruit skin irrespective of the age of fruit. Furthermore, the application of hydrogen peroxide significantly increased the stiffness of skin strips excised from fruit of an age when endogenous peroxidase isozymes associated with the termination of growth are first detected. The results support the hypothesis that the tomato fruit skin plays an integral role in the regulation of tomato fruit growth, and that changes in its mechanical properties may be mediated by peroxidase. As far as is known, this is the first demonstration that peroxidases alter the mechanical properties of the plant cell wall.

Journal of Experimental Botany

4417511

10.1038/NATURE08943

Molecular Basis of Infrared Detection by Snakes

Snakes possess a unique sensory system for detecting infrared radiation, enabling them to generate a ‘thermal image’ of predators or prey. Infrared signals are initially received by the pit organ, a highly specialized facial structure that is innervated by nerve fibres of the somatosensory system. How this organ detects and transduces infrared signals into nerve impulses is not known. Here we use an unbiased transcriptional profiling approach to identify TRPA1 channels as infrared receptors on sensory nerve fibres that innervate the pit organ. TRPA1 orthologues from pit-bearing snakes (vipers, pythons and boas) are the most heat-sensitive vertebrate ion channels thus far identified, consistent with their role as primary transducers of infrared stimuli. Thus, snakes detect infrared signals through a mechanism involving radiant heating of the pit organ, rather than photochemical transduction. These findings illustrate the broad evolutionary tuning of transient receptor potential (TRP) channels as thermosensors in the vertebrate nervous system.

Nature

9769939

10.1242/JEB.01286

Spatial vision in the echinoid genus Echinometra

SUMMARY Although eyes are generally considered necessary for image resolution, a diffuse photoreceptive system with directional sensitivity may also have this ability. Two species of the echinoid genus Echinometra were tested for spatial vision by examining their ability to locate and move towards targets of different sizes. The echinoids were significantly oriented (P<0.0001) towards a target with an angular width of 33° (0.3 sr) but were not oriented to targets with angular widths of 26° and 16°. This ability is probably due to the blocking of off-angle light by the spines, which have approximately the correct spacing for the observed resolution. Spatial vision is advantageous for echinoids of this genus because they leave and return to small dark shelters. This first demonstration of spatial vision in an echinoderm sheds further light on the complex optical structures and photobehaviors found in this phylum.

The Journal of Experimental Biology

18881128

10.4319/LO.2012.57.1.0221

Nitrogen transformations in a through‐flow wetland revealed using whole‐ecosystem pulsed 15N additions

We used pulsed and continuous additions of 15N together with whole-ecosystem metabolism measurements to elucidate the mechanisms of nitrogen (N) transformations in a small (1170 m2) through-flow wetland situated along a stream. From measurements of the wetland inflow and outflow, we observed a consistent decrease in nitrate (by 10% of inflow concentrations), while ammonium increased by an order of magnitude. Outflow ammonium concentrations oscillated in a diel cycle, inverse to the concentration of dissolved oxygen (i.e., greater ammonium export at night). The pulsed 15N additions showed little uptake of nitrate over time in the wetland and rapid daytime uptake of ammonium from the water column (rate constant, kt 5 0.11 h21). A steady-state 15Nammonium addition demonstrated a similar rate of ammonium uptake (kt 5 0.067 h21), no detectable nitrification, and highlighted the spatial pattern of ammonium and nitrate uptake within the wetland. Porewater concentration profiles suggest high rates of net ammonium diffusion from the sediments. Ecosystem metabolism measurements indicate that release was attenuated during the day by autotrophic uptake, resulting in lower ammonium export during the day. Denitrification rates were modeled from dissolved N2 : Ar ratios, but they were not sufficient to account for the observed loss in nitrate. Nitrate was removed near the pond inflow but not actively cycled throughout the pond, while the balance between sediment release and subsequent uptake of ammonium from the water-column dominated N cycling in this wetland.

Limnology and Oceanography

28127158

10.1016/0040-8166(74)90004-4

The fine structure of Odonata chromatophores.

Abstract The appearance, fine structure and pigment composition of the epidermal chromatophores of mature Austrolestes annulosus (Lestidae) are described and compared with the developing chromatophores of teneral Austrolestes and the mature chromatophores of Diphlebia lestoides (Amphipterygidae) and Ischnura heterosticta (Caenagrionidae). Mature chromatophores contain masses of near spherical light-scattering bodies and larger irregularly shaped pigment vesicles. These effect colour change by migrating in opposite directions, through a system of interconnecting granular endoplasmic reticulum tubules. The pigment, a mixture of xanthommatin and dihydroxanthommatin, has a liquid or gelatinous consistency. Developing chromatophores of teneral insects lack light-scattering bodies and well-defined migratory pigment vesicles, but contain irregular masses of pigment of similar chemical composition.

Tissue & Cell

40162265

10.1073/PNAS.0906699106

Structural plasticity and catalysis regulation of a thermosensor histidine kinase

Temperature sensing is essential for the survival of living cells. A major challenge is to understand how a biological thermometer processes thermal information to optimize cellular functions. Using structural and biochemical approaches, we show that the thermosensitive histidine kinase, DesK, from Bacillus subtilis is cold-activated through specific interhelical rearrangements in its central four-helix bundle domain. As revealed by the crystal structures of DesK in different functional states, the plasticity of this helical domain influences the catalytic activities of the protein, either by modifying the mobility of the ATP-binding domains for autokinase activity or by modulating binding of the cognate response regulator to sustain the phosphotransferase and phosphatase activities. The structural and biochemical data suggest a model in which the transmembrane sensor domain of DesK promotes these structural changes through conformational signals transmitted by the membrane-connecting two-helical coiled-coil, ultimately controlling the alternation between output autokinase and phosphatase activities. The structural comparison of the different DesK variants indicates that incoming signals can take the form of helix rotations and asymmetric helical bends similar to those reported for other sensing systems, suggesting that a similar switching mechanism could be operational in a wide range of sensor histidine kinases.

Proceedings of the National Academy of Sciences of the United States of America

41219379

10.1007/BF00340948

The mineralization and hardness of the radular teeth of the limpet Patella vulgata L.

SummaryA study of the Patella vulgata radula has been made using: the scanning electron microscope in its normal and compositional contrast modes of operation, the electron microprobe analyser, ion etching with argon ions and microhardness testing.Only iron, silicon and small amounts of sulphur were detected in the radula. The teeth can be subdivided into a cusp, a junctional area where the cusp is joined to the base, and the base which is embedded in the radular membrane. From a study of longitudinal vertical and transverse sections of the mature teeth it was found that the cusp could be subdivided into a posterior iron-rich area (44–51% Fe, 1–6% Si) and an anterior silicon-rich area (22–30% Fe, 27–32% Si). The junctional zone consisted of a poorly mineralised layer at its border with the cusp and an iron-rich layer where it joined the base. The upper part of the base (5% Fe, 16% Si) could be clearly differentiated from the silicon-rich anterior and lower parts of the base (3–4% Fe, 28–35% Si). No minerals were detected in the membrane. The changes in the mineral content of the teeth cusps along the length of the radula were studied. Iron appeared in the cusps at the 25th row and the concentration increased to 28% at the 50th row. The iron was here evenly distributed throughout the cusp. Silicon appeared in the anterior part of the cusp at the 50th row and as it increased in concentration so the iron was displaced, and at the same time the concentration of iron increased in the posterior part of the cusp. Mineralization appeared to be complete by the 150th row.The teeth cusps appear to consist of 800 Å fibres grouped into 1μ thick bundles and the tooth appears to be covered by a thin enamel-like layer. It is suggested that the fibres contain the silicon-rich phase and the matrix the iron-rich phase.The significance of the arrangement of the fibres and the distribution of the minerals are discussed with relation to the function of the teeth.

Cell and Tissue Research

14001250

10.1126/SCIENCE.1075433

High Abrasion Resistance with Sparse Mineralization: Copper Biomineral in Worm Jaws

Biominerals are widely exploited to harden or stiffen tissues in living organisms, with calcium-, silicon-, and iron-based minerals being most common. In notable contrast, the jaws of the marine bloodworm Glycera dibranchiata contain the copper-based biomineral atacamite [Cu2(OH)3Cl]. Polycrystalline fibers are oriented with the outer contour of the jaw. Using nanoindentation, we show that the mineral has a structural role and enhances hardness and stiffness. Despite the low degree of mineralization, bloodworm jaws exhibit an extraordinary resistance to abrasion, significantly exceeding that of vertebrate dentin and approaching that of tooth enamel.

Science

22104806

10.1002/BIO.715

Stimulation of DNA repair as an evolutionary drive for bacterial luminescence.

It was demonstrated recently that luminescence of a free-living marine bacterium, Vibrio harveyi, stimulates DNA repair, most probably by activation of the photoreactivation process. Here, we ask whether the stimulation of DNA repair could be an evolutionary drive that ensured maintenance and development of early bacterial luminescent systems. To test this hypothesis, we cultivated V. harveyi lux(+) bacteria and luxA mutants in mixed cultures. Initial cultures were mixed to obtain a culture consisting of roughly 50% lux(+) cells and 50% luxA mutants. Then bacteria were cultivated for several days and ratio of luminescent to dark bacteria was measured. Under these conditions, luxA mutants became highly predominant within a few days of cultivation. This indicates that, without a selective pressure, the luminescence is a disadvantage for bacteria, perhaps due to consumption of significant portion of cell energy. However, when the same experiments were repeated but cultures were irradiated with low UV doses, luminescent bacteria started to predominate shortly after the irradiation. Therefore, we conclude that stimulation of photoreactivation may be an evolutionary drive for bacterial bioluminescence.

Luminescence

35363042

10.1113/JPHYSIOL.1968.SP008626

The influence of the nasal mucosa and the carotid rete upon hypothalamic temperature in sheep

1. In chronically‐prepared sheep, intracranial temperatures were measured in the cavernous sinus among the vessels of the carotid rete and at the circle of Willis extravascularly, and in the preoptic area and in other brain stem regions. Extracranial temperatures were measured intravascularly in the carotid or internal maxillary arteries and on the nasal mucosa and the skin of the ear.

The Journal of Physiology

36343044

10.1023/A:1006259402496

The dehesa system of southern Spain and Portugal as a natural ecosystem mimic

The dehesas of the southwestern Iberian Peninsula are 'man-made' ecosystems characterised by a savannah-like physiognomy. The trees are viewed as an integrated part of the system, and as a result are planted, managed, and regularly pruned. Palynological and historical evidence of the manipulation of initial ecosystems by man to obtain a savannah-like ecosystem is presented. The ecological functions of the tree are detailed using results obtained at two complementary scales. At the local scale, strong soil structural differences and functional differences in water budget and patterns of water use are observed under and outside the tree canopy. Using the concept of ecosystem mimicry, the two coexistent components of dehesas can be compared to two distant stages of a secondary succession characterised by very different behaviours. At the regional scale, evidence of relationships between tree density and mean annual precipitation over more than 5000 km2 suggests that the structure of these man-made agroecosystems have adjusted over the long-term and correspond to an optimal functional equilibrium based on the hydrological equilibrium hypothesis. Finally, the future of dehesas in the face of contemporary exogenous threats of economic and global environmental origin is discussed.

Agroforestry Systems

4401455

10.1038/35099670

Energy saving in flight formation

Many species of large bird fly together in formation, perhaps because flight power demands and energy expenditure can be reduced when the birds fly at an optimal spacing, or because orientation is improved by communication within groups. We have measured heart rates as an estimate of energy expenditure in imprinted great white pelicans (Pelecanus onocrotalus) trained to fly in 'V' formation, and show that these birds save a significant amount of energy by flying in formation. This advantage is probably a principal reason for the evolution of flight formation in large birds that migrate in groups.

Nature

44406321

10.1177/0748730408320263

Circadian Regulation of Bioluminescence in the Prey-Luring Glowworm, Arachnocampa flava

The glowworms of New Zealand and Australia are bioluminescent fly larvae that generate light to attract prey into their webs. Some species inhabit the constant darkness of caves as well as the dim, natural photophase of rain-forests. Given the diversity of light regimens experienced by glowworms in their natural environment, true circadian rhythmicity of light output could be present. Consequently the light emission characteristics of the Australian subtropical species Arachnocampa flava, both in their natural rainforest habitat and in artificial conditions in the laboratory, were established. Larvae were taken from rainforest and kept alive in individual containers. When placed in constant darkness (DD) in the laboratory they maintained free-running, cyclical light output for at least 28 days, indicating that light output is regulated by an endogenous rhythm. The characteristics of the light emission changed in DD: individuals showed an increase in the time spent glowing per day and a reduction in the maximum light output. Most individuals show a free-running period greater than 24 h. Manipulation of the photophase and exposure to skeleton photoperiods showed that light acts as both a masking and an entraining agent and suggests that the underlying circadian rhythm is sinusoidal in the absence of light-based masking. Manipulation of thermoperiod in DD showed that temperature cycles are an alternative entraining agent. Exposure to a period of daily feeding in DD failed to entrain the rhythm in the laboratory. The endogenous regulation of luminescence poses questions about periodicity and synchronization of bioluminescence in cave glowworms.

Journal of Biological Rhythms

15205370

10.1073/PNAS.1000615107

Discovering the flight autostabilizer of fruit flies by inducing aerial stumbles

Just as the Wright brothers implemented controls to achieve stable airplane flight, flying insects have evolved behavioral strategies that ensure recovery from flight disturbances. Pioneering studies performed on tethered and dissected insects demonstrate that the sensory, neurological, and musculoskeletal systems play important roles in flight control. Such studies, however, cannot produce an integrative model of insect flight stability because they do not incorporate the interaction of these systems with free-flight aerodynamics. We directly investigate control and stability through the application of torque impulses to freely flying fruit flies (Drosophila melanogaster) and measurement of their behavioral response. High-speed video and a new motion tracking method capture the aerial “stumble,” and we discover that flies respond to gentle disturbances by accurately returning to their original orientation. These insects take advantage of a stabilizing aerodynamic influence and active torque generation to recover their heading to within 2° in < 60 ms. To explain this recovery behavior, we form a feedback control model that includes the fly’s ability to sense body rotations, process this information, and actuate the wing motions that generate corrective aerodynamic torque. Thus, like early man-made aircraft and modern fighter jets, the fruit fly employs an automatic stabilization scheme that reacts to short time-scale disturbances.

Proceedings of the National Academy of Sciences of the United States of America

13143214

10.1242/JEB.045088

Characterization of mechanisms for Ca2+ and HCO3–/CO32– acquisition for shell formation in embryos of the freshwater common pond snail Lymnaea stagnalis

SUMMARY The freshwater common pond snail Lymnaea stagnalis produces embryos that complete direct development, hatching as shell-bearing individuals within 10 days despite relatively low ambient calcium and carbonate availability. This development is impaired by removal of ambient total calcium but not by removal of bicarbonate and/or carbonate. In this study we utilized pharmacological agents to target possible acquisition pathways for both Ca2+ and accumulation of carbonate in post-metamorphic, shell-laying embryos. Using whole egg mass flux measurements and ion-specific microelectrode analytical techniques, we have demonstrated that carbonic anhydrase-catalyzed hydration of CO2 is central in the acquisition of both shell-forming ions because it provides the hydrogen ions for an electrogenic vacuolar-type H+-ATPase that fuels the uptake of Ca2+ via voltage-dependent Ca2+ channels and possibly an electrogenic Ca2+/1H+ exchanger. Additionally, CO2 hydration provides an endogenous source of HCO –3. Thus, hydration of endogenous CO2 forms HCO –3 for calcification while hydrogen ions are excreted, contributing to continued Ca2+ uptake, as well as creating favorable alkaline internal conditions for calcification. The connections between Ca2+ and HCO –3 acquisition mechanisms that we describe here provide new insight into this efficient, embryonic calcification in freshwater.

The Journal of Experimental Biology

45383993

10.1065/ESPR2004.08.213

Utilising the Synergy between Plants and Rhizosphere Microorganisms to Enhance Breakdown of Organic Pollutants in the Environment (15 pp)

Background Phytoremediation is a promising technology for the cleanup of polluted environments. The technology has so far been used mainly to remove toxic heavy metals from contaminated soil, but there is a growing interest in broadening its applications to remove/degrade organic pollutants in the environment. Both plants and soil microorganisms have certain limitations with respect to their individual abilities to remove/breakdown organic compounds. A synergistic action by both rhizosphere microorganisms that leads to increased availability of hydrophobic compounds, and plants that leads to their removal and/or degradation, may overcome many of the limitations, and thus provide a useful basis for enhancing remediation of contaminated environments.Main Features The review of literature presented in this article provides an insight to the nature of plant-microbial interactions in the rhizosphere, with a focus on those processes that are relevant to the breakdown and/or removal of organic pollutants. Due consideration has been given to identify opportunities for utilising the plant-microbial synergy in the rhizosphere to enhance remediation of contaminated environments.Results and Discussion The literature review has highlighted the existence of a synergistic interaction between plants and microbial communities in the rhizosphere. This interaction benefits both microorganisms through provision of nutrients by root exudates, and plants through enhanced nutrient uptake and reduced toxicity of soil contaminants. The ability of the plant-microbial interaction to tackle some of the most recalcitrant organic chemicals is of particular interest with regard to enhancing and extending the scope of remediation technologies.Conclusions Plant-microbial interactions in the rhizosphere offer very useful means for remediating environments contaminated with recalcitrant organic compounds.Outlook A better knowledge of plant-microbial interactions will provide a basis for improving the efficacy of biological remediations. Further research is, however, needed to investigate different feedback mechanisms that select and regulate microbial activity in the rhizosphere.

Environmental Science and Pollution Research

1151173

10.1242/JEB.034280

Hierarchical organisation of the trap in the protocarnivorous plant Roridula gorgonias (Roridulaceae)

SUMMARY The flypaper trap of the protocarnivorous plant Roridula gorgonias is known to capture various insects, even those having a considerable body size, by using an adhesive, visco-elastic resinous secretion released by glandular trichomes of different dimensions. However, recent experimental studies have shown that the adhesion of long tentacle-shaped trichome secretion is not as strong as previously assumed. One may then ask why this flypaper trap is so highly effective. In the present study, we compared geometry, flexibility and the adhesive properties of secretion in different sized trichomes. We have analysed the gross morphology of the plant and its surfaces using light and cryo-scanning electron microscopy. Trichomes' stiffness and the adhesive properties of their secretion on different surfaces were measured. A combination of structural and experimental results, presented in this study, let us suggest that R. gorgonias represents a three-dimensional trap consisting of three functional hierarchical levels (plant, leaves and trichomes). According to their size, we classified three types of trichomes having a particular arrangement on the leaf. The longest trichomes are more flexible and less adhesive compared with the shortest ones. The latter are 48 times stiffer and their secretion has a 9 times higher adhesive strength. Our data support the hypothesis that the shortest trichomes are adapted to strong, long-term adherence to prey insects, and that the longest trichomes are responsible for initial trapping and entanglement function.

The Journal of Experimental Biology

205414286

10.1002/ARCH.20267

Proteinaceous adhesive secretions from insects, and in particular the egg attachment glue of Opodiphthera sp. moths.

Biochemical and electrophoretic screening of 29 adhesive secretions from Australian insects identified six types that appeared to consist largely of protein. Most were involved in terrestrial egg attachment. Hydrogel glues were subjected to gravimetric analyses and assessed for overall amino acid composition. When 32 proteins in glues from eight insect species were analyzed individually, many proved to be rich in Gly, Ser, and/or Pro, and some contained substantial levels of 4-hydroxyproline. A few proteins were heavily glycosylated. Abundant protein-based secretions were tested as adhesives, mainly by measuring dry shear strength on wood. The strongest (1-2 MPa) was an egg attachment glue produced by saturniid gum moths of the genus Opodiphthera. It was harvested from female colleterial gland reservoirs as a treacle-like liquid that underwent irreversible gelation, and recovered from the capsules of laid eggs as a highly elastic orange-brown hydrogel that could also display high tack. Its protein-based nature was confirmed and explored by spectroscopy, enzymatic degradation, and 2D gel electrophoresis. Its proteins are mostly 80-95 kDa, and sequences (almost all novel) were established for 23 tryptic peptides. Scanning probe microscopy of Opodiphthera hydrogel in water returned median values of 0.83 nN for adhesion, 63 kPa for modulus, and 87% for resilience. Recombinant mimics of this material might be useful as biodegradable commodity adhesives or as specialty biomedical products.

Archives of Insect Biochemistry and Physiology

21198441

10.1021/JP809138S

Probing the molecular and electronic structure of norhipposudoric and hipposudoric acids from the red sweat of Hippopotamus amphibius: a DFT investigation.

Molecular structure and tautomeric/conformational preferences of norhipposudoric and hipposudoric acids, the recently isolated pigments of the Hippopotamus amphibius' sweat, were investigated using the density functional theory (DFT) PBE0 formalism. Among a large variety of possible structures, two similar keto-enol tautomer/conformers are nearly isoenergetic and markedly more stable than the others both in the gas phase and aqueous solution. The bulk solvent effect was accounted for with the polarizable continuum model (PCM). A distinctive structural feature is the strong intramolecular hydrogen bonding in the keto-enol O-H...O bridge, as shown by analysis of the atoms-in-molecules topological properties of the electron density. To elucidate the claimed strong acidity of these pigments, the site-specific microscopic dissociation constants were also calculated using the cluster-continuum model, a hybrid approach based on inclusion of explicit solvent molecules and solvation of the cluster by the dielectric continuum. Notably, the first deprotonation should occur predominantly from the enolic group with a remarkably low pk(i) value. This factor could play an important role in the potent antibiotic activity of the pigments. The absorption spectra of the undissociated and dissociated compounds in aqueous solution were interpreted with time-dependent DFT/PCM calculations. The pi-pi* diquinoid excitations, mainly occurring in the fluorenoid nucleus, are the major contributors to the color and strong absorption bands in the UVA and UVB regions, which are closely related to the efficient sunscreen activity exerted by the pigments.

Journal of Physical Chemistry A

12809459

10.1002/CSSC.201100040

Editorial: A current perspective on photocatalysis.

The efficient conversion of solar photons into solar electricity and solar fuels is one of the most important scientific challenges of this century owing to dwindling fossil fuel reserves and the need for clean energy. While research in the direct conversion of solar energy to electricity in the areas of low-cost photovoltaic (PV) systems based on all-inorganic semiconductors, dye-sensitized solar cells, organic, and molecular PV is more technically advanced than its direct conversion to fuels, electricity may not be the ultimate primary solar energy conversion choice owing to the intermittence of solar radiation, the considerable energy loss during transmission, the availability of cost-effective storage media for electricity, and the continuing need for liquid transportation fuels. On the other hand, the direct conversion of solar photons to fuels such as H{sub 2}, CO, alcohols, and hydrocarbons using H{sub 2}O and CO{sub 2} as feedstocks offers a solution for the storage and distribution of solar energy in the form of stable chemical bonds that can be activated to provide energy at arbitrary times and locations. The latter approach to photocatalysis is generally called artificial photosynthesis, and has received renewed interest over the past five or so years. While 'photocatalysis' has not traditionallymore » been restricted to the generation of 'solar fuels,' and has included the production of other useful chemicals, polymerization, and environmental remediation applications, the recent upsurge of interest has been driven mostly by renewable energy issues. It was the pioneering work on photo-electrochemical splitting of water to H{sub 2} and O{sub 2} by n-type TiO{sub 2} using ultraviolet light, by Fujishima and Honda in 1972, that ushered in the area of research that has come to be known as 'solar fuels,' and that has led to the terms 'photocatalysis' and 'solar fuels' becoming almost synonymous. This special issue of ChemSusChem is devoted to providing a current perspective on the field of photocatalysis. It contains invited papers from leading researchers in a wide range of important aspects of the field that address materials, photophysical, photochemical, and electrocatalysis issues. The area remains primarily the domain of basic research studies because progress toward the promise offered by the early work has (at least until recently) been slow, despite its significance having become increasingly recognized. The present collection of papers deals with new semiconductor photocatalysts, molecular catalysts for hydrogen production and water oxidation, dye-sensitized photoelectrochemical cells, and electrochemical CO{sub 2} reduction. Overall photochemical water splitting without any applied bias potential is achieved in several systems, especially under UV irradiation. Further advances are also achieved in a few semiconductor systems, such as GaZn oxynitrides or two-step (so-called 'Z-scheme') systems to produce H{sub 2} and O{sub 2} without any sacrificial reagent under visible irradiation. When band gaps of semiconductors are narrowed to absorb more visible light for greater efficiency, or when band positions are not suitable for carrying out one-electron redox processes, multielectron catalysts are required to promote proton-coupled electron transfer reactions in producing solar fuels. In homogeneous photocatalysis systems, sacrificial reagents are typically used to investigate the catalytic activity, detailed kinetics, and mechanisms of a half reaction. Photoelectrolysis systems with immobilized catalysts (metals, metal oxides, or molecular catalysts) on electrodes can separate oxidized products, such as O{sub 2}, and reduced products, such as H{sub 2}, CO, CH{sub 3}OH, and others, by means of proton- or hydroxide-conducting membranes. The following paragraphs briefly summarize these contributions. In the area of UV-driven water splitting, Townsend et al. prepared Pt-and/or IrO{sub x}-coated niobate (Nb{sub 6}O{sub 17}{sup 4-}) nanoscrolls and tested photochemical water reduction with methanol as a sacrificial reagent, and water oxidation with AgNO{sub 3} as a sacrificial reagent. In this work, factors for improving the limited photocatalytic activity of the system are explored. Nishiyama et al. investigated factors controlling the photocatalytic water splitting activity, such as preparation temperature and crystallinity of the semiconductor materials, the amount of co-catalyst loading, and the degree of dispersion of the co-catalyst with RuO{sub 2}-loaded niobium and tantalum bronzes, M{sub 8}P{sub 4}O{sub 32}{sup 4-} (M=Nb, Ta). Their DFT calculations demonstrate that severe distortion of NbO{sub 6} octahedra plays an important role in photocatalytic water splitting.« less

Chemsuschem

204997705

10.1038/27111

Young wallabies get a free ride

Wallabies and kangaroos increase their speed of hopping with little increase in their use of metabolic energy, apparently by means of elastic energy savings in their hindlimb tendons,. Here we report that, because of this storage capacity, female tammar wallabies can carry large young in their pouch at very low cost, with no increase in metabolic energy expenditure.

Nature

88314986

10.2307/2259780

Interactions of woody and herbaceous vegetation in a southern African Savanna

(1) A number of plots were set up in two natural savanna communities, with identical climates but different soils, to examine possible competition between the woody and herbaceous components of the vegetation. The community on the more sandy soil is a broad-leaf woody savanna and the other a more open microphyllous Acacia community. (2) Vegetative growth and soil water were monitored over a 2-year period in control plots and in plots cleared of one of the vegetation components. (3) In the broad-leaf community the effect of the herbaceous vegetation on the woody plants is negligible. (4) In the Acacia community with seven times more herbaceous biomass, mature woody-plant growth was reduced by competition from the grass-dominated herb layer particularly in the first (wetter) year. The vertical root distributions and soil-water data indicate that the grasses take up topsoil (0-30 cm) water sufficiently rapidly to reduce drainage into the subsoil (30-130 cm), and that they also take up subsoil water directly, thus lowering the amount of subsoil water available to woody plants. (5) The different herbaceous to woody-plant biomass ratios in the two sites and the different intensity of competition during the 2 years can be explained in terms of the effects of the soil properties and of the rainfall intensity on the ratio of water in the topsoil to that in the subsoil.

Journal of Ecology

20233522

10.1016/J.CUB.2012.01.010

High-resolution polarisation vision in a cuttlefish

Summary For animals that can see it, the polarisation of light adds another dimension to vision, analogous to adding colour to a black and white image [1,2]. Whilst some animals use the orientation of the electric field vector (e-vector) for navigation and orientation [3], the ability to discriminate angular differences in e-vector has been implicated in object recognition for predator/prey detection [4,5] as well as signalling and communication [6]. In all animals previously tested, however, the resolution of e-vector angle discrimination has been found to be in the range 10–20° [5,7,8], which is inadequate for the typical e-vector differences measured in relevant natural visual scenes [9]. In this study, we found that mourning cuttlefish ( Sepia plangon ) are able to detect differences between e-vector orientations as small as 1°. Not only is this the most acute e-vector angle discrimination measured behaviourally in any animal, but it provides a high enough resolution to be relevant to real world visual tasks. We analysed natural underwater scenes using computer based polarisation imaging. When we increased the resolution of our system, we discovered information not detected using normal-resolution imaging polarimetry and invisible to animals lacking fine e-vector angle discrimination. For example, we found that high-resolution e-vector discrimination provides a new way of breaking typical intensity-based background matching. S. plangon lacks colour vision, like most other cephalopods, and high-resolution polarisation vision may provide an alternative source of contrast information that is just as fine-scale.

Current Biology

29804900

10.1073/PNAS.1010335107

Skeletal development in sloths and the evolution of mammalian vertebral patterning

Mammals show a very low level of variation in vertebral count, particularly in the neck. Phenotypes exhibited at various stages during the development of the axial skeleton may play a key role in testing mechanisms recently proposed to explain this conservatism. Here, we provide osteogenetic data that identify developmental criteria with which to recognize cervical vs. noncervical vertebrae in mammals. Except for sloths, all mammals show the late ossification of the caudal-most centra in the neck after other centra and neural arches. In sloths with 8–10 ribless neck vertebrae, the caudal-most neck centra ossify early, matching the pattern observed in cranial thoracic vertebrae of other mammals. Accordingly, we interpret the ribless neck vertebrae of three-toed sloths caudal to V7 as thoracic based on our developmental criterion. Applied to the unusual vertebral phenotype of long-necked sloths, these data support the interpretation that elements of the axial skeleton with origins from distinct mesodermal tissues have repatterned over the course of evolution.

Proceedings of the National Academy of Sciences of the United States of America

44003786

10.1242/JEB.050310

Honeybee flight: a novel ‘streamlining’ response

SUMMARY Animals that move rapidly through the air can save considerable energy by reducing the drag that they need to overcome during flight. We describe a novel ‘streamlining’ response in tethered, flying honeybees in which the abdomen is held in a raised position when the visual system is exposed to a pattern of image motion that is characteristic of forward flight. This visually evoked response, which can be elicited without exposing the insect to any airflow, presumably serves to reduce the aerodynamic drag that would otherwise be produced by the abdomen during real flight. The response is critically dependent on the presence of appropriate image motion everywhere within the large field of view of the insect. Thus, our results also underscore the importance of using panoramic stimulation for the study of visually guided flight in insects, and reveal the relative importance of various regions of the visual field in assessing the speed of flight through the environment.

The Journal of Experimental Biology

36290314

10.1016/J.JEMBE.2010.03.009

Phantom hunter of the fjords: Camouflage by counterillumination in a shark (Etmopterus spinax)

Many midwater animals emit ventral light to hide their silhouette in the water column. This phenomenon known as counterillumination typically requires fine control over light emission since it needs a luminescence that closely matches the properties of downwelling light (intensity, angular distribution and wavelength). Here we provide evidence that, although lacking complex structures of counterilluminating animals, the deepwater luminescent shark Etmopterus spinax could, in Norwegian fjords, efficiently cloak its silhouette from downwelling ambient light to remain hidden from predator and prey. This represents the first experimentally tested function of luminescence in a shark and illustrates how evolution can take different routes to converge on identical complex behavior. (C) 2010 Elsevier B.V. All rights reserved.

Journal of Experimental Marine Biology and Ecology

29096692

10.1126/SCIENCE.AAA6683

Why the seahorse tail is square

The curious tale of the square tail Appendages in animals are typically round, but the seahorse tail has a square cross section. Porter et al. hypothesize that this shape provides better functionality and strength than a round cross section (see the Perspective by Ashley-Ross). Three-dimensional printed models show that square cross section shapes behave more advantageously when subjected to compressive forces. By allowing greater deformation without damage and accommodating twisting deformations, square appendages passively return to their original configurations. The added flexibility of the square cross section enhances the tail's ability to grasp objects. Science, this issue 10.1126/science.aaa6683; see also p. 30 3D-printed models show that square profile seahorse tails have better crush resistance and grasping ability than do circular ones. [Also see Perspective by Ashley-Ross] INTRODUCTION Although the predominant shapes of most animal tails are cylindrical, seahorse tails are square prisms. The skeleton of their tails consists of a bony armor arranged into several ringlike segments composed of four L-shaped plates that surround a central vertebra. These plates articulate with specialized joints that facilitate bending and twisting, as well as resist vertebral fracture from crushing. Muscles attached to the vertebral column transmit forces to the bony plates to provide motion for grasping and holding on to objects such as sea grasses, mangrove roots, and coral reefs, which allows them to hide and rely on camouflage when evading predators and capturing prey. RATIONALE We hypothesize that the square cross-sectional architecture of a seahorse tail improves mechanical performance in prehension (grasping ability) and armored functions (crushing resistance), relative to a cylindrical one. To test this hypothesis, we evaluated the mechanics of two three-dimensional (3D)–printed prototypes composed of articulating plates and vertebrae that mimic the natural (square prism) and a hypothetical (cylindrical) tail structure. We compared the bending, twisting, and compressive behavior of the biomimetic prototypes to show that the square profile is better than the circular one for two integrated functions: grasping ability and crushing resistance. RESULTS Seahorse tails (and the prototypes) have three primary joints that enable motion: ball-and-socket, peg-and-socket, and gliding. The ball-and-socket joints connect adjacent vertebrae and constrain bending in both the square and cylindrical prototypes to the same degree, exhibiting a behavior similar to that of a natural seahorse tail. The peg-and-socket joints connect the plates of adjacent segments and substantially restrict twisting in the prototype with a square profile, as compared with the circular one. The square geometry limits excessive torsion and preserves articulatory organization, which could provide seahorses a natural safety factor against torsion-induced damage and assist in tail relaxation. Further, the square architecture is flat (increasing surface contact) and undergoes an exterior shape change when twisted, which could allow seahorses to grasp objects with more control. Gliding joints are present at the plate overlaps along all four sides of both prototypes. Under transverse compression and impact (with a rubber mallet), the plates of the square prototype slide past one another with one degree of translation freedom (analogous to the crushing behavior of a natural seahorse tail), exhibiting a response that is stiffer, stronger, and more resilient than its cylindrical counterpart, whose plates translate and rotate on impact. CONCLUSION Exploration of these biologically inspired designs provides insight into the mechanical benefits for seahorses to have evolved prehensile tails composed of armored plates organized into square prisms. Beyond their intended practical applications, engineering designs are convenient means to answer elusive biological questions when live animal data are unavailable (for example, seahorses do not have cylindrical tails). Understanding the role of mechanics in these prototypes may help engineers to develop future seahorse-inspired technologies that mimic the prehensile and armored functions of the natural appendage for a variety of applications in robotics, defense systems, or biomedicine. Engineering designs answer biological questions. 3D-printed models that mimic a seahorse tail were designed not only for potential engineering applications but also to answer the biological question, why might tails organized into square prisms be better than cylinders? A mechanical comparison of the prototypes shows that articulated square prisms perform better than do cylinders for grasping and resistance to crushing. Whereas the predominant shapes of most animal tails are cylindrical, seahorse tails are square prisms. Seahorses use their tails as flexible grasping appendages, in spite of a rigid bony armor that fully encases their bodies. We explore the mechanics of two three-dimensional–printed models that mimic either the natural (square prism) or hypothetical (cylindrical) architecture of a seahorse tail to uncover whether or not the square geometry provides any functional advantages. Our results show that the square prism is more resilient when crushed and provides a mechanism for preserving articulatory organization upon extensive bending and twisting, as compared with its cylindrical counterpart. Thus, the square architecture is better than the circular one in the context of two integrated functions: grasping ability and crushing resistance.

Science

44117715

10.1038/S41598-018-26571-6

Iridescence impairs object recognition in bumblebees

Iridescence is a taxonomically widespread and striking form of animal coloration, yet despite advances in understanding its mechanism, its function and adaptive value are poorly understood. We test a counterintuitive hypothesis about the function of iridescence: that it can act as camouflage through interference with object recognition. Using an established insect visual model (Bombus terrestris), we demonstrate that both diffraction grating and multilayer iridescence impair shape recognition (although not the more subtle form of diffraction grating seen in some flowers), supporting the idea that both strategies can be effective means of camouflage. We conclude that iridescence produces visual signals that can confuse potential predators, and this might explain the high frequency of iridescence in many animal taxa.

Scientific Reports

24888144

10.2307/1543095

Peptides controlling stifness of connective tissue in sea cucumbers.

We present the first evidence of a system of four bioactive peptides that affect the stiffness of sea cucumber dermis. The body wall dermis of sea cucumbers consists of catch connective tissue that is characterized by quick and drastic stiffness changes under nervous control. The peptides were isolated from the body wall, their amino acid sequences determined, and identical peptides synthesized. Two peptides, which we named holokinins, are homologous with bradykinin. We tested the effect of the peptides on the mechanical properties of sea cucumber dermis. Both of the holokinins softened the dermis, and a pentapeptide that we designated as NGIWYamide stiffened it. Both effects were reversibly suppressed by anesthesia with menthol. We called the fourth peptide stichopin; it had no direct effect on the stiffness of the dermis but suppressed action of the neurotransmitter acetylcholine reversibly. The results suggest that the peptides are neuropeptides and are part of a sophisticated system of neurotransmitters and neuromodulators that controls the connective tissue stiffness of sea cucumber dermis.

The Biological Bulletin

84069826

10.1111/J.1474-919X.1997.TB04663.X

Surface tension prey transport in shorebirds: how widespread is it?

Surface tension prey transport is a feeding mechanism employing the surface tension of water surrounding prey to transport prey from bill tip to mouth. Previously, it has been demonstrated only in the Red-necked Phalarope Phalaropus lobatus. On the basis of a model of the bill morphology necessary for this method of prey transport, I suggest that many species of shorebird should be capable of surface tension feeding. Laboratory investigations of the feeding mechanics of Wilson's Phalarope Phalaropus tricolor, Western Sandpiper Calidris mauri and Least Sandpiper Calidris minutilla demonstrated that all three use surface tension transport of prey when feeding in water. I examined interspecific variation in the performance of this feeding mechanism with a high-speed video system and a customized motion analysis system. Exploratory analyses indicated significant interspecific variation in distance the prey is transported per cycle of mandibular spreading, gape increase per unit transport, speed of transport, total number of cycles necessary to complete transport and total time to complete transport. The calidrid sandpipers also occasionally used other feeding mechanisms in conjunction with surface tension transport of prey. The discovery that these sandpipers, which normally obtain prey by probing, are capable of surface tension transport of prey implies that the capacity to employ this feeding mechanism may be widespread in the Scolopacidae and may have been a significant factor in the evolutionary radiation of phalaropes into aquatic environments.

Ibis

14860326

10.3390/ROBOTICS5030015

Biomimetic Spider Leg Joints: A Review from Biomechanical Research to Compliant Robotic Actuators

Due to their inherent compliance, soft actuated joints are becoming increasingly important for robotic applications, especially when human-robot-interactions are expected. Several of these flexible actuators are inspired by biological models. One perfect showpiece for biomimetic robots is the spider leg, because it combines lightweight design and graceful movements with powerful and dynamic actuation. Building on this motivation, the review article focuses on compliant robotic joints inspired by the function principle of the spider leg. The mechanism is introduced by an overview of existing biological and biomechanical research. Thereupon a classification of robots that are bio-inspired by spider joints is presented. Based on this, the biomimetic robot applications referring to the spider principle are identified and discussed.

Robotics

86312909

10.1111/J.1570-7458.2012.01314.X

Do western boxelder bugs sunbathe for sanitation? Inferences from in vitro experiments

When western boxelder bugs, Boisea rubrolineata (Barber) (Hemiptera: Rhopalidae), form aggregations in warm sunlight, they release from their posterior dorsal abdominal gland an odorous blend of monoterpenes with heretofore unknown biological function. In laboratory analyses and experiments, we show that bugs in warm sunlight, but not in shade, exude and spread copious amounts of monoterpenes onto their cuticle. These monoterpenes do not serve as a pheromone, but rather as a means of sanitation. They inhibit germination of conidia of the fungal pathogen Beauveria bassiana (Bals.‐Criv.) Vuill. (Hypocreales) as well as halt the growth of germinated spores. This prophylactic defense against pathogens appears adaptive for phytophagous insects, like B. rubrolineata, that are prone to infections by microbes thriving on leaf surfaces and in the insects' overwintering microhabitat.

Entomologia Experimentalis Et Applicata

10383314

10.1098/RSBL.2009.0311

Tree shrew lavatories: a novel nitrogen sequestration strategy in a tropical pitcher plant

Nepenthes pitcher plants are typically carnivorous, producing pitchers with varying combinations of epicuticular wax crystals, viscoelastic fluids and slippery peristomes to trap arthropod prey, especially ants. However, ant densities are low in tropical montane habitats, thereby limiting the potential benefits of the carnivorous syndrome. Nepenthes lowii, a montane species from Borneo, produces two types of pitchers that differ greatly in form and function. Pitchers produced by immature plants conform to the ‘typical’ Nepenthes pattern, catching arthropod prey. However, pitchers produced by mature N. lowii plants lack the features associated with carnivory and are instead visited by tree shrews, which defaecate into them after feeding on exudates that accumulate on the pitcher lid. We tested the hypothesis that tree shrew faeces represent a significant nitrogen (N) source for N. lowii, finding that it accounts for between 57 and 100 per cent of foliar N in mature N. lowii plants. Thus, N. lowii employs a diversified N sequestration strategy, gaining access to a N source that is not available to sympatric congeners. The interaction between N. lowii and tree shrews appears to be a mutualism based on the exchange of food sources that are scarce in their montane habitat.

Biology Letters

5031201

10.1073/PNAS.0703535104

Molecular sabotage of plant defense by aphid saliva

Aphids, which constitute one of the most important groups of agricultural pests, ingest nutrients from sieve tubes, the photoassimilate transport conduits in plants. Aphids are able to successfully puncture sieve tubes with their piercing mouthparts (stylets) and ingest phloem sap without eliciting the sieve tubes' normal occlusion response to injury. Occlusion mechanisms are calcium-triggered and may be prevented by chemical constituents in aphid saliva injected into sieve tubes before and during feeding. We recorded aphid feeding behavior with the electrical penetration graph (EPG) technique and then experimentally induced sieve tube plugging. Initiation of sieve tube occlusion caused a change in aphid behavior from phloem sap ingestion to secretion of watery saliva. Direct proof of “unplugging” properties of aphid saliva was provided by the effect of aphid saliva on forisomes. Forisomes are proteinaceous inclusions in sieve tubes of legumes that show calcium-regulated changes in conformation between a contracted state (below calcium threshold) that does not occlude the sieve tubes and a dispersed state (above calcium threshold) that occludes the sieve tubes. We demonstrated in vitro that aphid saliva induces dispersed forisomes to revert back to the nonplugging contracted state. Labeling Western-blotted saliva proteins with 45Ca2+ or ruthenium red inferred the presence of calcium-binding domains. These results demonstrate that aphid saliva has the ability to prevent sieve tube plugging by molecular interactions between salivary proteins and calcium. This provides aphids with access to a continuous flow of phloem sap and is a critical adaptation instrumental in the evolutionary success of aphids.

Proceedings of the National Academy of Sciences of the United States of America

31547154

10.1007/S00114-004-0539-3

Honeybee combs: construction through a liquid equilibrium process?

Geometrical investigations of honeycombs and speculations on how honeybees measure and construct the hexagons and rhombi of their cells are centuries old. Here we show that honeybees neither have to measure nor construct the highly regular structures of a honeycomb, and that the observed pattern of combs can be parsimoniously explained by wax flowing in liquid equilibrium. The structure of the combs of honeybees results from wax as a thermoplastic building medium, which softens and hardens as a result of increasing and decreasing temperatures. It flows among an array of transient, close-packed cylinders which are actually the self-heated honeybees themselves. The three apparent rhomboids forming the base of each cell do not exist but arise as optical artefacts from looking through semi-transparent combs.

Naturwissenschaften

32848104

10.1126/SCIENCE.1125878

Biomineralization of Gold: Biofilms on Bacterioform Gold

Bacterial biofilms are associated with secondary gold grains from two sites in Australia. 16S ribosomal DNA clones of the genus Ralstonia that bear 99% similarity to the bacterium Ralstonia metallidurans—shown to precipitate gold from aqueous gold(III) tetrachloride—were present on all DNA-positive gold grains but were not detected in the surrounding soils. These results provide evidence for the bacterial contribution to the authigenic formation of secondary bacterioform gold grains and nuggets.

Science

199022591

10.3389/FPHYS.2019.00972

Insect Odorscapes: From Plant Volatiles to Natural Olfactory Scenes

Olfaction is an essential sensory modality for insects and their olfactory environment is mostly made up of plant-emitted volatiles. The terrestrial vegetation produces an amazing diversity of volatile compounds, which are then transported, mixed, and degraded in the atmosphere. Each insect species expresses a set of olfactory receptors that bind part of the volatile compounds present in its habitat. Insect odorscapes are thus defined as species-specific olfactory spaces, dependent on the local habitat, and dynamic in time. Manipulations of pest-insect odorscapes are a promising approach to answer the strong demand for pesticide-free plant-protection strategies. Moreover, understanding their olfactory environment becomes a major concern in the context of global change and environmental stresses to insect populations. A considerable amount of information is available on the identity of volatiles mediating biotic interactions that involve insects. However, in the large body of research devoted to understanding how insects use olfaction to locate resources, an integrative vision of the olfactory environment has rarely been reached. This article aims to better apprehend the nature of the insect odorscape and its importance to insect behavioral ecology by reviewing the literature specific to different disciplines from plant ecophysiology to insect neuroethology. First, we discuss the determinants of odorscape composition, from the production of volatiles by plants (section “Plant Metabolism and Volatile Emissions”) to their filtering during detection by the olfactory system of insects (section “Insect Olfaction: How Volatile Plant Compounds Are Encoded and Integrated by the Olfactory System”). We then summarize the physical and chemical processes by which volatile chemicals distribute in space (section “Transportation of Volatile Plant Compounds and Spatial Aspects of the Odorscape”) and time (section “Temporal Aspects: The Dynamics of the Odorscape”) in the atmosphere. The following sections consider the ecological importance of background odors in odorscapes and how insects adapt to their olfactory environment. Habitat provides an odor background and a sensory context that modulate the responses of insects to pheromones and other olfactory signals (section “Ecological Importance of Odorscapes”). In addition, insects do not respond inflexibly to single elements in their odorscape but integrate several components of their environment (section “Plasticity and Adaptation to Complex and Variable Odorscapes”). We finally discuss existing methods of odorscape manipulation for sustainable pest insect control and potential future developments in the context of agroecology (section “Odorscapes in Plant Protection and Agroecology”).

Frontiers in Physiology

17597338

10.1038/NCHEM.822

Photoelectrochemical complexes for solar energy conversion that chemically and autonomously regenerate

Naturally occurring photosynthetic systems use elaborate pathways of self-repair to limit the impact of photo-damage. Herein, we demonstrate a complex that mimics this process consisting of two recombinant proteins, phospholipids and a carbon nanotube. The components self-assemble into a configuration in which an array of lipid bilayers aggregate on the surface of the carbon nanotube, creating a platform for the attachment of light-converting proteins. The system can disassemble upon the addition of a surfactant and reassemble on its removal over an indefinite number of cycles. The assembly is thermodynamically meta-stable and can only transition reversibly if the rate of surfactant removal exceeds about 10−5 sec−1. Only in the assembled state do the complexes exhibit photoelectrochemical activity. We demonstrate a regeneration cycle that uses surfactant to switch between assembled and disassembled states, resulting in increased photo-conversion efficiency of more than 300% over 168 hours and an indefinite extension of the system's lifetime.

Nature Chemistry

211088903

10.1038/S41467-020-14547-Y

Macrophages employ quorum licensing to regulate collective activation

Macrophage-initiated inflammation is tightly regulated to eliminate threats such as infections while suppressing harmful immune activation. However, individual cells’ signaling responses to pro-inflammatory cues are heterogeneous, with subpopulations emerging with high or low activation states. Here, we use single-cell tracking and dynamical modeling to develop and validate a revised model for lipopolysaccharide (LPS)-induced macrophage activation that invokes a mechanism we term quorum licensing. The results show that bimodal phenotypic partitioning of macrophages is primed during the resting state, dependent on cumulative history of cell density, predicted by extrinsic noise in transcription factor expression, and independent of canonical LPS-induced intercellular feedback in the tumor necrosis factor (TNF) response. Our analysis shows how this density-dependent coupling produces a nonlinear effect on collective TNF production. We speculate that by linking macrophage density to activation, this mechanism could amplify local responses to threats and prevent false alarms. Macrophage activation is tightly regulated to maintain immune homeostasis, yet activation is also heterogeneous. Here, the authors show that macrophages coordinate activation by partitioning into two phenotypes that can nonlinearly amplify collective inflammatory cytokine production as a function of cell density.

Nature Communications

41424815

10.1038/NCHEMBIO0207-86

The most versatile of all reactive intermediates?

The iron(II)- and 2-oxoglutarate-dependent oxygenases catalyze varied oxidative reactions. Spectroscopic analyses on the catalytic cycle of the chlorinating enzyme CytC3 reveal the presence of chloride–iron(IV)–oxo complexes, expanding the scope of chemistry known to be catalyzed by non-heme iron-oxo species.

Nature Chemical Biology

17503148

10.1242/JEB.01795

Cloning, characterization and expression of escapin, a broadly antimicrobial FAD-containing l-amino acid oxidase from ink of the sea hare Aplysia californica

SUMMARY A 60 kDa monomeric protein isolated from the defensive purple ink secretion of the sea hare Aplysia californica was cloned and sequenced, and is the first sea hare antimicrobial protein to be functionally expressed in E. coli. Sequence analysis suggested that this protein is a flavin-containing l-amino acid oxidase (LAAO), with one predicted potential glycosylation site, although the glycosylation could not be experimentally confirmed. This protein, which we call `escapin', has high sequence similarity to several other gastropod proteins. Escapin was verified by NMR, mass spectroscopy and HPLC to have FAD as its flavin cofactor. Escapin's antimicrobial effects, bacteriostasis and bactericidal, were determined using a combination of two assays: (1) incubation of bacteria on solid media followed by assessment of inhibition by direct observation of zones of inhibition or by turbidity measurements; and (2) incubation of bacteria in liquid media followed by counting viable colonies after growing on agar plates. Native escapin inhibited the growth of Gram-positive and Gram-negative bacteria, including marine bacteria (Vibrio harveyii and Staphylococcus aureus) and pathogenic bacteria (Staphylococcus aureus, Streptococcus pyogenes and Pseudomonas aeruginosa). Escapin also inhibited the growth of yeast and fungi, with different efficacies. Escapin's antimicrobial activity was concentration dependent and did not decrease when stored for more than 5 months at room temperature. Escapin was bacteriostatic and not bactericidal in minimal media (e.g. salt media) with glucose, yeast extract, and a mixture of 20 amino acids each at 50 μmol l-1, but was bactericidal in media enriched with Tryptone Peptone. Escapin was also strongly bactericidal in media with l-lysine at concentrations as low as 3 mmol l-1 and slightly bactericidal in 50 mmol l-1 l-arginine, but not in most other amino acids even at 50 mmol l-1. Escapin had high oxidase activity (producing hydrogen peroxide) with either l-arginine or l-lysine as a substrate and little to no oxidase activity with other l-amino acids. Hydrogen peroxide alone (without escapin or amino acids) was strongly bacteriostatic but poorly bactericidal, similar in this respect to l-arginine but different from l-lysine in the presence of escapin. Together these results suggest that there are multiple mechanisms to escapin's antimicrobial effects, with bacteriostasis resulting largely or entirely from the effects of hydrogen peroxide produced by escapin's LAAO activity, but bactericidal effects resulting from lysine-dependent mechanisms not directly involving hydrogen peroxide. Recombinant escapin expressed in bacteria was also active against Gram-positive and Gram-negative bacteria, suggesting that glycosylation is not essential for antimicrobial activity.

The Journal of Experimental Biology

43368862

10.1016/S0956-5663(01)00284-6

Biosensing of opioids using frog melanophores.

Spectacular color changes of fishes, frogs and other lower vertebrates are due to the motile activities of specialized pigment containing cells. Pigment cells are interesting for biosensing purposes since they provide an easily monitored physiological phenomenon. Melanophores, containing dark brown melanin pigment granules, constitute an important class of chromatophores. Their melanin-filled pigment granules may be stimulated to undergo rapid dispersion throughout the melanophores (cells appear dark), or aggregation to the center of the melanophores (cells appear light). This simple physiological response can easily be measured in a photometer. Selected G protein coupled receptors can be functionally expressed in cultured frog melanophores. Here, we demonstrate the use of recombinant frog melanophores as a biosensor for the detection of opioids. Melanophores were transfected with the human opioid receptor 3 and used for opiate detection. The response to the opioid receptor agonist morphine and a synthetic opioid peptide was analyzed by absorbance readings in an aggregation assay. It was shown that both agonists caused aggregation of pigment granules in the melanophores, and the cells appeared lighter. The pharmacology of the expressed receptors was very similar to its mammalian counterpart, as evidenced by competitive inhibition by increasing concentrations of the opioid receptor inhibitor naloxone. Transfection of melanophores with selected receptors enables the creation of numerous melanophore biosensors, which respond selectively to certain substances. The melanophore biosensor has potential use for measurement of substances in body fluids such as saliva, blood plasma and urine.

Biosensors and Bioelectronics

21054231

10.1140/EPJE/I2014-14109-Y

Dew condensation on desert beetle skin

Some tenebrionind beetles inhabiting the Namib desert are known for using their body to collect water droplets from wind-blown fogs. We aim to determine whether dew water collection is also possible for desert insects. For this purpose, we investigated the infra-red emissivity, and the wetting and structural properties, of the surface of the elytra of a preserved specimen of Physasterna cribripes (Tenebrionidæ) beetle, where the macro-structure appears as a series of “bumps”, with “valleys” between them. Dew formation experiments were carried out in a condensation chamber. The surface properties (infra-red emissivity, wetting properties) were dominated by the wax at the elytra surface and, to a lower extent, its micro-structure. We performed scanning electron microscope on histological sections and determined the infra-red emissivity using a scanning pyrometer. The emissivity measured (0.95±0.07 between 8–14μm) was close to the black body value. Dew formation occurred on the insect’s elytra, which can be explained by these surface properties. From the surface coverage of the condensed drops it was found that dew forms primarily in the valleys between the bumps. The difference in droplet nucleation rate between bumps and valleys can be attributed to the hexagonal microstructure on the surface of the valleys, whereas the surface of the bumps is smooth. The drops can slide when they reach a critical size, and be collected at the insect's mouth.Graphical abstract

European Physical Journal E

273825

10.1186/1741-7007-8-109

A mixed community of actinomycetes produce multiple antibiotics for the fungus farming ant Acromyrmex octospinosus

BackgroundAttine ants live in an intensely studied tripartite mutualism with the fungus Leucoagaricus gongylophorus, which provides food to the ants, and with antibiotic-producing actinomycete bacteria. One hypothesis suggests that bacteria from the genus Pseudonocardia are the sole, co-evolved mutualists of attine ants and are transmitted vertically by the queens. A recent study identified a Pseudonocardia-produced antifungal, named dentigerumycin, associated with the lower attine Apterostigma dentigerum consistent with the idea that co-evolved Pseudonocardia make novel antibiotics. An alternative possibility is that attine ants sample actinomycete bacteria from the soil, selecting and maintaining those species that make useful antibiotics. Consistent with this idea, a Streptomyces species associated with the higher attine Acromyrmex octospinosus was recently shown to produce the well-known antifungal candicidin. Candicidin production is widespread in environmental isolates of Streptomyces, so this could either be an environmental contaminant or evidence of recruitment of useful actinomycetes from the environment. It should be noted that the two possibilities for actinomycete acquisition are not necessarily mutually exclusive.ResultsIn order to test these possibilities we isolated bacteria from a geographically distinct population of A. octospinosus and identified a candicidin-producing Streptomyces species, which suggests that they are common mutualists of attine ants, most probably recruited from the environment. We also identified a Pseudonocardia species in the same ant colony that produces an unusual polyene antifungal, providing evidence for co-evolution of Pseudonocardia with A. octospinosus.ConclusionsOur results show that a combination of co-evolution and environmental sampling results in the diversity of actinomycete symbionts and antibiotics associated with attine ants.

BMC Biology

83541536

10.1080/08927014.1998.9522865

Physiological ecology of nest construction and protein flow in pre-emergence colonies of Polistes chinensis (Hymenoptera Vespidae): effects of rainfall and microclimates

The amount of oral secretion, which mostly consists of proteinaceous materials, used for the construction and maintenance of nests by foundresses of Polistes chinensis was analysed in 95 field nests (1994–1996). The amounts always exceeded 50% of mean percent secretion to total the dry nest weights, and it was greater in nests built at sites exposed to direct rainfall than in those at sheltered sites. Further, exposed nests built in 1995 (a rainy year) were much smaller than those of 1994 and 1996, and the amount of secretion in that year was much greater than in the other years. The nitrogen content of adult workers, immatures, those left inside cells and the oral secretion in nests of 1996 showed that 10–20% of total protein resources brought in during the founding phase may be devoted to producing the secretion. The results suggest that the foundresses may regulate the amounts of oral secretion used for such purposes in response to environmental conditions.

Ethology Ecology & Evolution

83982687

10.1890/0012-9658(2001)082[1720:ESOALV]2.0.CO;2

EVOLUTIONARY SIGNIFICANCE OF AWN LENGTH VARIATION IN A CLONAL GRASS OF FIRE-PRONE SAVANNAS

We investigated the selective advantage of continuous variation of awn length in the clonal grass Hyparrhenia diplandra (Poaceae) in a West African tropical savanna (Ivory Coast) that burns every year. This species is apomictic, so all seeds produced by one mother plant have the same genotype. H. diplandra produces diaspores with a hygroscopic awn whose length varies within and among plants. In other grass species, awns play a significant role in secondary dispersal on the ground and in seed burial. Using an experimental approach, we quantified (1) the environmental and genetic components of awn length variation, (2) the influence of awn length variation on seed burial depth, (3) the effect of awn length on seed germination and seedling survival rates in burned and unburned plots, and (4) the potential role of fire intensity in selecting diaspores with different awn lengths. Awn length varied from 35 to 70 mm and was highly heritable (h2 = 0.63). Variation within individuals was not related to flowering p...

Ecology

24826682

10.1006/ANBE.2000.1542

Individually recognizable scent marks on flowers made by a solitary bee

The marking of flowers with ephemeral scent is an underappreciated but vital element in the foraging behaviour of social bees. Using observational and experimental data, we tested whether a solitary bee (female Anthophora plumipes) uses scent marking while foraging on flowers of Cerinthe major in Portugal. Females used scent marks with at least two components that differed in their volatility and, furthermore, recognized the marks of different individuals. A very short-term component (<3 min) was attractive, resulting in the observed high level of immediate revisits: this component appeared to be adjusted according to the foraging needs of the moment. A longer-term component (<30 min) was initially repellent and matched the rate of nectar renewal; it, or the response to it, also appeared to be adjusted to the perceived level of nectar reward. There may be even longer-term effects associated with the specific foraging areas of individual bees. Observed differences in the way in which individuals responded to scent marks indicate that they may play a role as part of a dominance or exclusion mechanism among females. Copyright 2001 The Association for the Study of Animal Behaviour.

Animal Behaviour

4430261

10.1038/NATURE09686

Nanoscale chemical tomography of buried organic–inorganic interfaces in the chiton tooth

Biological organisms possess an unparalleled ability to control the structure and properties of mineralized tissues. They are able, for example, to guide the formation of smoothly curving single crystals or tough, lightweight, self-repairing skeletal elements. In many biominerals, an organic matrix interacts with the mineral as it forms, controls its morphology and polymorph, and is occluded during mineralization. The remarkable functional properties of the resulting composites—such as outstanding fracture toughness and wear resistance—can be attributed to buried organic–inorganic interfaces at multiple hierarchical levels. Analysing and controlling such interfaces at the nanometre length scale is critical also in emerging organic electronic and photovoltaic hybrid materials. However, elucidating the structural and chemical complexity of buried organic–inorganic interfaces presents a challenge to state-of-the-art imaging techniques. Here we show that pulsed-laser atom-probe tomography reveals three-dimensional chemical maps of organic fibres with a diameter of 5–10 nm in the surrounding nano-crystalline magnetite (Fe3O4) mineral in the tooth of a marine mollusc, the chiton Chaetopleura apiculata. Remarkably, most fibres co-localize with either sodium or magnesium. Furthermore, clustering of these cations in the fibre indicates a structural level of hierarchy previously undetected. Our results demonstrate that in the chiton tooth, individual organic fibres have different chemical compositions, and therefore probably different functional roles in controlling fibre formation and matrix–mineral interactions. Atom-probe tomography is able to detect this chemical/structural heterogeneity by virtue of its high three-dimensional spatial resolution and sensitivity across the periodic table. We anticipate that the quantitative analysis and visualization of nanometre-scale interfaces by laser-pulsed atom-probe tomography will contribute greatly to our understanding not only of biominerals (such as bone, dentine and enamel), but also of synthetic organic–inorganic composites.

Nature