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12521613

10.1088/1748-3182/5/3/035005

Fish schooling as a basis for vertical axis wind turbine farm design.

Most wind farms consist of horizontal axis wind turbines (HAWTs) due to the high power coefficient (mechanical power output divided by the power of the free-stream air through the turbine cross-sectional area) of an isolated turbine. However when in close proximity to neighboring turbines, HAWTs suffer from a reduced power coefficient. In contrast, previous research on vertical axis wind turbines (VAWTs) suggests that closely spaced VAWTs may experience only small decreases (or even increases) in an individual turbine's power coefficient when placed in close proximity to neighbors, thus yielding much higher power outputs for a given area of land. A potential flow model of inter-VAWT interactions is developed to investigate the effect of changes in VAWT spatial arrangement on the array performance coefficient, which compares the expected average power coefficient of turbines in an array to a spatially isolated turbine. A geometric arrangement based on the configuration of shed vortices in the wake of schooling fish is shown to significantly increase the array performance coefficient based upon an array of 16 x 16 wind turbines. The results suggest increases in power output of over one order of magnitude for a given area of land as compared to HAWTs.

arXiv: Fluid Dynamics

4353856

10.1038/28303

Seal whiskers detect water movements

How do pinnipeds orientate themselves under water? As most pinniped species feed in conditions under which visibility is drastically reduced, for example at night, at great depths or in murky waters, it has been particularly unclear how they succeed in finding food. Here we show that harbour seals (Phoca vitulina) can use their whiskers to detect minute water movements. The high sensitivity of this sensory system should allow a seal to gain hydrodynamic information resulting from movements of other aquatic animals, such as prey, predators or conspecifics.

Nature

45859307

10.1021/PR101285N

There are abundant antimicrobial peptides in brains of two kinds of Bombina toads.

It is well-known that there is a large amount of antimicrobial peptides in amphibian skins but few antimicrobial peptides are found in amphibian brains. Twenty-two and four antimicrobial peptides were purified and characterized from the brain homogenate of Bombina maxima and B. microdeladigitora, respectively. One hundred fifty-eight cDNA clones encoding 79 antimicrobial peptides were isolated from brain cDNA libraries of B. maxima and B. microdeladigitora. These antimicrobial peptides belong to two peptide groups (maximin and maximin-H). Twenty of them are identical to previously reported antimicrobial peptides (maximin 1-8, 10, 11, maximin H1, 3-5, 7, 9, 10, 12, 15, 16) from B. maxima skin secretions. Fifty-nine of them are novel antimicrobial peptides. Some of these antimicrobial peptides showed strong antimicrobial activities against tested microorganism strains including Gram-positive and -negative bacteria and fungi. The current diversity in peptide coding cDNA sequences is, to our knowledge, the most extreme yet described for any animal brains. The extreme diversity may give rise to interest to prospect the actual functions of antimicrobial peptides in amphibian brains.

Journal of Proteome Research

44649565

10.1152/AJPREGU.1986.251.6.R1228

Ionic compensation with no renal response to chronic hypercapnia in chrysemys picta bellii.

The ionic compensatory response to CO2 breathing for 3 days was studied on intact and cystectomized turtles at 10 and 20 degrees C. Arterial blood gases, pH, ionized calcium, and the plasma concentrations of Na+, K+, Cl-, total Ca2+, and total Mg2+ were measured periodically. At 20 degrees C, ureteral urine was also collected from bladderless turtles and was analyzed for pH, ions, NH3+, total CO2, osmolality, and titratable acid. When CO2 was breathed there was a compensatory change in the strong-ion difference as manifest by an increase in plasma [HCO3-] that was approximately 10 meq/l both in the 10 and 20 degrees C turtles. The only significant associated strong-ion changes observed consistent with the ionic compensatory response were increases in total and ionized Ca2+ and total Mg2+. These results were unaffected at either temperature by surgical removal of the urinary bladder. Urine collected from cystectomized turtles showed no compensatory increase in acid excretion during hypercapnia; in fact, changes occurred in the opposite direction. Urinary excretion of HCO3- and urine pH increased significantly, whereas titratable acidity decreased significantly. No significant change occurred in ammonia excretion over the three days of hypercapnia. These data argue against compensatory roles for the kidneys and urinary bladder in this species and point to internal ionic exchanges involving bone and shell.

American Journal of Physiology-regulatory Integrative and Comparative Physiology

140140896

10.1007/978-3-642-71630-0_5

Simple and diversified crop rotations: approach and insight into agroecosystems

Farm management and the cultivation of soils for production of fiber and food for men and animais has always raised the question of how far man can interfere with the household of nature without disturbing the basis of vital processes. As hunter and gatherer, man’s influence on nature or natural ecosystems was of little importance. As soon as the world population increased, other methods and forms of producing food developed, namely those of modern agriculture.

Ecological studies

85039824

10.1016/J.JTHERBIO.2010.03.002

Thermal windows on the body surface of African elephants (Loxodonta africana) studied by infrared thermography.

Abstract In this study, we examined infrared thermograms in the course of time of six African zoo elephants and observed two phenomena. First, we noticed independent thermal windows, highly vascularised skin areas, on the whole elephants’ body and second we observed distinct and sharply delimited hot sections on the elephants’ pinnae. The frequency of thermal windows increased with increasing ambient temperature and body weight. We assume that the restriction of an enhanced cutaneous blood flow to thermal windows might enable the animal to react more flexibly to its needs with regard to heat loss. With this understanding, the use of thermal windows in heat loss might be seen as a fine-tuning mechanism under thermoneutral conditions.

Journal of Thermal Biology

5713215

10.1098/RSBL.2010.0844

Discovery of skin alkaloids in a miniaturized eleutherodactylid frog from Cuba

Four phylogenetically independent lineages of frogs are currently known to sequester lipid-soluble skin alkaloids for which a dietary source has been demonstrated. We report here a remarkable fifth such instance, in Eleutherodactylus iberia and Eleutherodactylus orientalis, two species of miniaturized frogs of the family Eleutherodactylidae from Cuba. Six pumiliotoxins and two indolizidines were found in E. iberia, one of the smallest frogs in the world and characterized by a contrasting colour pattern for which we hypothesize an aposematic function. Analyses of stomach content indicated a numerical prevalence of mites with an important proportion of oribatids—a group of arthropods known to contain one of the pumiliotoxins detected in E. iberia. This suggests that miniaturization and specialization to small prey may have favoured the acquisition of dietary skin alkaloids in these amphibians.

Biology Letters

87534194

10.2307/2388261

Hurricane Hugo wind damage to southeastern U.S. coastal forest tree species

One percent of Hobcaw Forest, a 3077 ha tract in South Carolina's lower coastal plain, was inventoried with fixed area plots within four months after the eye of Hurricane Hugo passed 97 km south of the forest. Results of this sampling confirmed our hypotheses that the amount and nature of hurricane wind damage differed among the tree species sampled. Approximately 73 percent of the 16,870 trees inventoried were either not damaged or had light crown damage. Longleaf pine (Pinus palustris) was less damaged than loblolly pine (Pinus taeda) or pond pine (Pinus serotina). Bald cypress (Taxodium distichum) suffered light crown damage. Upland oaks were more heavily damaged than the pine species. Live oak (Quercus virginiana) was less damaged than laurel oak (Quercus laurifolia) and water oak (Quercus nigra). Those tree species commonly found in the lower coastal plain (longleaf pine, bald cypress, and live oak) suffered less damage than species with larger natural ranges.

Biotropica

19787942

10.1007/S00792-008-0143-0

Di-myo-inositol phosphate and novel UDP-sugars accumulate in the extreme hyperthermophile Pyrolobus fumarii

The archaeon Pyrolobus fumarii, one of the most extreme members of hyperthermophiles known thus far, is able to grow at temperatures up to 113°C. Over a decade after the description of this organism our knowledge about the structures and strategies underlying its remarkable thermal resistance remains incipient. The accumulation of a restricted number of charged organic solutes is a common response to heat stress in hyperthermophilic organisms and accordingly their role in thermoprotection has been often postulated. In this work, the organic solute pool of P. fumarii was characterized using 1H, 13C, and 31P NMR. Di-myo-inositol phosphate was the major solute (0.21 μmol/mg protein), reinforcing the correlation between the occurrence of this solute and hyperthermophily; in addition, UDP-sugars (total concentration 0.11 μmol/mg protein) were present. The structures of the two major UDP-sugars were identified as UDP-α-GlcNAc3NAc and UDP-α-GlcNAc3NAc-(4 ← 1)-β-GlcpNAc3NAc. Interestingly, the latter compound appears to be derived from the first one by addition of a 2,3-N-acetylglucoronic acid unit, suggesting that these UDP-sugars are intermediates of an N-linked glycosylation pathway. To our knowledge the UDP-disaccharide has not been reported elsewhere. The physiological roles of these organic solutes are discussed.

Extremophiles

3119587

10.1126/SCIENCE.1173036

Symbiotic Nitrogen Fixation in the Fungus Gardens of Leaf-Cutter Ants

Gardening for Ants and Termites Among the social insects, ants and termites are the most diverse and ecologically dominant. Termites are known to engage in a mutualism with nitrogen-fixing bacteria, and Pinto-Tomás et al. (p. 1120) have identified similar relationships occurring among leaf-cutter ants, which maintain specialized nitrogen-fixing bacteria in their fungus gardens. Together, these mutualisms are a major source of nitrogen in terrestrial ecosystems. How is the evolutionary stability of such mutualistic cooperation maintained? Aanen et al. (p. 1103) show that the Termitomyces fungus cultured by termites remains highly related because mycelia of the same clone fuse together and grow more efficiently to out-compete rare clones. Leaf-cutting ants engage in a mutualism with nitrogen-fixing bacteria that help fertilize their fungus gardens. Bacteria-mediated acquisition of atmospheric N2 serves as a critical source of nitrogen in terrestrial ecosystems. Here we reveal that symbiotic nitrogen fixation facilitates the cultivation of specialized fungal crops by leaf-cutter ants. By using acetylene reduction and stable isotope experiments, we demonstrated that N2 fixation occurred in the fungus gardens of eight leaf-cutter ant species and, further, that this fixed nitrogen was incorporated into ant biomass. Symbiotic N2-fixing bacteria were consistently isolated from the fungus gardens of 80 leaf-cutter ant colonies collected in Argentina, Costa Rica, and Panama. The discovery of N2 fixation within the leaf-cutter ant−microbe symbiosis reveals a previously unrecognized nitrogen source in neotropical ecosystems.

Science

121885772

10.1017/S1473550407003783

Adaptations to environmental extremes by multicellular organisms

Abstract Microbes, particularly Archaea, are well-known for their superb adaptation to extreme environments. However, amazing adaptations to extreme stresses do not only occur in microbes, but also in many multicellular organisms. Examples include tardigrades and their capability to survive freezing to near absolute zero, the Pompeii worm withstanding temperatures of up to 105°C, the Crucian carp remaining active in anoxic conditions for several months, and resurrection plants, which can survive near-complete desiccation. Here, we review some of the cryptobiotic strategies and adaptations exhibited in multicellular organisms, and point out their relevance to astrobiology.

International Journal of Astrobiology

25067275

10.1073/PNAS.1601624113

Mechanosensory hairs in bumblebees (Bombus terrestris) detect weak electric fields

Significance Electroreception in terrestrial animals is poorly understood. In bumblebees, the mechanical response of filiform hairs in the presence of electric fields provides key evidence for electrosensitivity to ecologically relevant electric fields. Mechanosensory hairs in arthropods have been shown to function as fluid flow or sound particle velocity receivers. The present work provides direct evidence for additional, nonexclusive functionality involving electrical Coulomb-force coupling between distant charged objects and mechanosensory hairs. Thus, the sensory mechanism is proposed to rely on electromechanical coupling, whereby many light thin hairs serve the detection of the electrical field surrounding a bumblebee approaching a flower. This finding prompts the possibility that other terrestrial animals use such sensory hairs to detect and respond to electric fields. Bumblebees (Bombus terrestris) use information from surrounding electric fields to make foraging decisions. Electroreception in air, a nonconductive medium, is a recently discovered sensory capacity of insects, yet the sensory mechanisms remain elusive. Here, we investigate two putative electric field sensors: antennae and mechanosensory hairs. Examining their mechanical and neural response, we show that electric fields cause deflections in both antennae and hairs. Hairs respond with a greater median velocity, displacement, and angular displacement than antennae. Extracellular recordings from the antennae do not show any electrophysiological correlates to these mechanical deflections. In contrast, hair deflections in response to an electric field elicited neural activity. Mechanical deflections of both hairs and antennae increase with the electric charge carried by the bumblebee. From this evidence, we conclude that sensory hairs are a site of electroreception in the bumblebee.

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

205691983

10.1038/SREP23539

Modelling of the frictional behaviour of the snake skin covered by anisotropic surface nanostructures

Previous experimental data clearly revealed anisotropic friction on the ventral scale surface of snakes. However, it is known that frictional properties of the ventral surface of the snake skin range in a very broad range and the degree of anisotropy ranges as well to a quite strong extent. This might be due to the variety of species studied, diversity of approaches used for the friction characterization, and/or due to the variety of substrates used as a counterpart in the experiments. In order to understand the interactions between the nanostructure arrays of the ventral surface of the snake skin, this study was undertaken, which is aimed at numerical modeling of frictional properties of the structurally anisotropic surfaces in contact with various size of asperities. The model shows that frictional anisotropy appears on the snake skin only on the substrates with a characteristic range of roughness, which is less or comparable with dimensions of the skin microstructure. In other words, scale of the skin relief should reflect an adaptation to the particular range of surfaces asperities of the substrate.

Scientific Reports

3352391

10.1007/S11160-009-9112-7

The biology of extinct and extant sawfish (Batoidea: Sclerorhynchidae and Pristidae)

Sclerorhynchids (extinct sawfishes, Batoidea), pristids (extant sawfish, Batoidea) and pristiophorids (sawsharks, Squalomorphi) are the three elasmobranch families that possess an elongated rostrum with lateral teeth. Sclerorhynchids are the extinct sawfishes of the Cretaceous period, which reached maximum total lengths of 100 cm. The morphology of their rostral teeth is highly variable. Pristid sawfish occur circumtropically and can reach maximum total lengths of around 700 cm. All pristid species are globally endangered due to their restricted habitat inshore. Pristiophorid sawsharks are small sharks of maximum total lengths below 150 cm, which occur in depths of 70–900 m. Close examination of the morphology of pectoral fin basals and the internal structure of the rostrum reveals that sclerorhynchids and pristids evolved independently from rhinobatids, whereas pristiophorids are squalomorph sharks. The elongation of the rostrum may be an adaptation for feeding, as all marine vertebrate taxa that possess this structure are said to use it in the context of feeding.

Reviews in Fish Biology and Fisheries

36740872

10.1103/PHYSREVE.76.017301

Micronanostructures of the scales on a mosquito's legs and their role in weight support.

We show here that the mosquito cannot only give rise to a higher water-supporting force than the water strider if the ratio of the water-supporting force to the body weight of the insect itself is compared, but also can safely take off or land on the water surface, and also can attach on any solid surface like the fly. We found that the mosquito's legs are covered by numerous scales consisting of the uniform microscale longitudinal ridges (nanoscale thickness and microscale spacing between) and nanoscale cross ribs (nanoscale thickness and spacing between). Such special delicate microstructure and/or nanostructure on the leg surface give a water contact angle of approximately 153 degrees and give a surprising high water-supporting ability. It was found that the water-supporting force of a single leg of the mosquito is about 23 times the body weight of the mosquito, compared with a water strider's leg giving a water-supporting force of about 15 times the body weight of the insect.

Physical Review E

706741

10.1038/NRM2417

Mechanisms of membrane fusion: disparate players and common principles

Membrane fusion can occur between cells, between different intracellular compartments, between intracellular compartments and the plasma membrane and between lipid-bound structures such as viral particles and cellular membranes. In order for membranes to fuse they must first be brought together. The more highly curved a membrane is, the more fusogenic it becomes. We discuss how proteins, including SNAREs, synaptotagmins and viral fusion proteins, might mediate close membrane apposition and induction of membrane curvature to drive diverse fusion processes. We also highlight common principles that can be derived from the analysis of the role of these proteins.

Nature Reviews Molecular Cell Biology

86952

10.1073/PNAS.0507398102

A spider that feeds indirectly on vertebrate blood by choosing female mosquitoes as prey.

Spiders do not feed directly on vertebrate blood, but a small East African jumping spider (Salticidae), Evarcha culicivora, feeds indirectly on vertebrate blood by choosing as preferred prey female mosquitoes that have had recent blood meals. Experiments show that this spider can identify its preferred prey by sight alone and by odor alone. When presented with two types of size-matched motionless lures, E. culicivora consistently chose blood-fed female mosquitoes in preference to nonmosquito prey, male mosquitoes, and sugar-fed female mosquitoes (i.e., females that had not been feeding on blood). When the choice was between mosquitoes of different sizes (both blood- or both sugar-fed), small juveniles chose the smaller prey, whereas adults and larger juveniles chose the larger prey. However, preference for blood took precedence over preference for size (i.e., to get a blood meal, small individuals took prey that were larger than the preferred size, and larger individuals took prey that were smaller than the preferred size). When presented with odor from two prey types, E. culicivora approached the odor from blood-fed female mosquitoes significantly more often the odor of the prey that were not carrying blood.

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

6731978

10.1242/JEB.036871

Correlation between aquaporin and water permeability in response to vasotocin, hydrin and β-adrenergic effectors in the ventral pelvic skin of the tree frog Hyla japonica

SUMMARY The ventral pelvic skin of the tree frog Hyla japonica expresses two kinds of arginine vasotocin (AVT)-stimulated aquaporins (AQP-h2 and AQP-h3), which affect the capacity of the frog's skin to absorb water. As such, it can be used as a model system for analyzing the molecular mechanisms of water permeability. We investigated AQP dynamics and water permeability in the pelvic skin of H. japonica following challenge with AVT, hydrins (intermediate peptides of pro-AVT) and β-adrenergic effectors. In the in vivo experiment, both AQP-h2 and AQP-h3 proteins were translocated to the apical plasma membrane in the principal cells of the first-reacting cell (FRC) layer in the pelvic skin following challenge with AVT, hydrin 1 and hydrin 2, thereby increasing the water permeability of the pelvic skin. The β-adrenergic receptor agonist isoproterenol (IP) and its anatagonist propranolol (PP) in combination with AVT or hydrins were used as challenge in the in vitro experiment. IP increased water permeability whereas PP inhibited it, and both events were well correlated with the translocation of the AQPs to the apical membrane. In the PP+AVT-treated skins, labels for AQP-h2 and AQP-h3 were differentially visible among the principal cells; the apical plasma membrane of some cells was labeled while others were not, indicating that the response of PP or AVT is different from cell to cell. These results provide morphological evidence that the principal cells of the FRC layers may have two kinds of receptors: a V2 receptor and β-adrenergic receptor.

The Journal of Experimental Biology

53185175

10.1016/J.ANBEHAV.2006.12.023

Nest ‘moulting’ in the ant Temnothorax albipennis

We showed how super-organisms, here ant colonies, modify their home according to their increasing or decreasing space requirements. The ontogeny of wall building by colonies of the ant Temnothorax albipennis involves discontinuous rebuilding events that are reminiscent of moulting in insects. Here for the first time we manipulated worker density by changing nest cavity size instead of worker number, thus avoiding accidentally shifting the balance of workers with different propensities for building tasks. Our results suggest for the first time that history influences wall building in ants when worker density decreases (e.g. with colony diminution) as well as when it increases (e.g. with colony growth) as shown by earlier work. Furthermore, we found that ants used a greater number of the larger building blocks (big sand grains) both after cavity expansion and, more surprisingly, also after cavity contraction. The pattern of nest ‘moulting’ we experimentally manipulated and analysed should provide insights into possible trade-offs between the various functions and structural properties of the nest that these animals may have to optimize.

Animal Behaviour

28126859

10.1126/SCIENCE.1212596

A Cultured Greigite-Producing Magnetotactic Bacterium in a Novel Group of Sulfate-Reducing Bacteria

The crystal structure of biomineralized magnetic nanocrystals depends on environmental and genetic factors. Magnetotactic bacteria contain magnetosomes—intracellular, membrane-bounded, magnetic nanocrystals of magnetite (Fe3O4) or greigite (Fe3S4)—that cause the bacteria to swim along geomagnetic field lines. We isolated a greigite-producing magnetotactic bacterium from a brackish spring in Death Valley National Park, California, USA, strain BW-1, that is able to biomineralize greigite and magnetite depending on culture conditions. A phylogenetic comparison of BW-1 and similar uncultured greigite- and/or magnetite-producing magnetotactic bacteria from freshwater to hypersaline habitats shows that these organisms represent a previously unknown group of sulfate-reducing bacteria in the Deltaproteobacteria. Genomic analysis of BW-1 reveals the presence of two different magnetosome gene clusters, suggesting that one may be responsible for greigite biomineralization and the other for magnetite.

Science

85069637

10.1080/00306525.1969.9639116

THE USE OF MUD IN NEST-BUILDING—A REVIEW OF THE INCIDENCE AND TAXONOMIC IMPORTANCE

Ostrich

5160502

10.1088/1748-3182/2/3/L01

Renewable fluid dynamic energy derived from aquatic animal locomotion.

Aquatic animals swimming in isolation and in groups are known to extract energy from the vortices in environmental flows, significantly reducing muscle activity required for locomotion. A model for the vortex dynamics associated with this phenomenon is developed, showing that the energy extraction mechanism can be described by simple criteria governing the kinematics of the vortices relative to the body in the flow. In this way, we need not make direct appeal to the fluid dynamics, which can be more difficult to evaluate than the kinematics. Examples of these principles as exhibited in swimming fish and existing energy conversion devices are described. A benefit of the developed framework is that the potentially infinite-dimensional parameter space of the fluid-structure interaction is reduced to a maximum of eight combinations of three parameters. The model may potentially aid in the design and evaluation of unsteady aero- and hydrodynamic energy conversion systems that surpass the Betz efficiency limit of steady fluid dynamic energy conversion systems.

Bioinspiration & Biomimetics

21799740

10.1016/S0021-9290(99)00013-5

Nanoscale design of snake skin for reptation locomotions via friction anisotropy.

Multi-mode scanning probe microscopy is employed to investigate the nanostructure of dermal samples from three types of snakes. Sophisticated friction modifying nanostructures are described. These include an ordered microfibrillar array that can function to achieve mission adaptable friction characteristics. Significant reduction of adhesive forces in the contact areas caused by the 'double-ridge' nanoscale microfibrillar geometry provides ideal conditions for sliding in forward direction with minimum adhesive forces and friction. Low surface adhesion in these local contact points may reduce local wear and skin contamination by environmental debris. The highly asymmetric, 'pawl-like' profile of the microfibrillar ends with radius of curvature 20-40 nm induces friction anisotropy in forward backward motions and serves as an effective stopper for backward motion preserving low friction for forward motion. The system of continuous micropores penetrating through the snake skin may serve as a delivery system for lubrication/anti-adhesive lipid mixture that provides for boundary lubrication of snake skins.

Journal of Biomechanics

109198122

10.1016/J.ENGFRACMECH.2006.02.007

Teacher tree: The evolution of notch shape optimization from complex to simple

Abstract Shape optimization of engineering components following the design rules of nature was started in the late eighties in the Karlsruhe Research Centre. The key idea was the natural observation that trees care by load-adaptive growth to maintain a uniform stress distribution at their surface. This means also that high stress peaks (notch stresses) are avoided as potential failure points. The computer simulation of this adaptive growth has been called Computer Aided Optimization (CAO). CAO is based on the use of the Finite-Element-Method (FEM). The present paper shows how 15 years after the CAO-method drastic simplifications are available. So notch shape optimization in many cases can be done without the FEM-codes, with a pocket calculator or even simpler with a graphic method.

Engineering Fracture Mechanics

6593834

10.1098/RSPB.2010.0214

Plant green-island phenotype induced by leaf-miners is mediated by bacterial symbionts

The life cycles of many organisms are constrained by the seasonality of resources. This is particularly true for leaf-mining herbivorous insects that use deciduous leaves to fuel growth and reproduction even beyond leaf fall. Our results suggest that an intimate association with bacterial endosymbionts might be their way of coping with nutritional constraints to ensure successful development in an otherwise senescent environment. We show that the phytophagous leaf-mining moth Phyllonorycter blancardella (Lepidoptera) relies on bacterial endosymbionts, most likely Wolbachia, to manipulate the physiology of its host plant resulting in the ‘green-island’ phenotype—photosynthetically active green patches in otherwise senescent leaves—and to increase its fitness. Curing leaf-miners of their symbiotic partner resulted in the absence of green-island formation on leaves, increased compensatory larval feeding and higher insect mortality. Our results suggest that bacteria impact green-island induction through manipulation of cytokinin levels. This is the first time, to our knowledge, that insect bacterial endosymbionts have been associated with plant physiology.

Proceedings of The Royal Society B: Biological Sciences

53533862

10.1111/J.1365-2435.2007.01249.X

The biomechanics of Cornus canadensis stamens are ideal for catapulting pollen vertically

Summary 1 Rapid movements in fungi and plants have evolved in different species to facilitate the dispersal of spores and seeds. The mechanisms of action can differ among species, but the effectiveness of these movements has rarely, if ever, been tested. Here we show through a quantitative biomechanical analysis that the stamens of Cornus canadensis L. (bunchberry) are ideal for catapulting pollen vertically at high speeds. 2 We develop a biomechanical model to describe the explosive launch of pollen from the flowers of bunchberry. The model determines the equation of motion for the stamens based only on the morphology and measurements of the parts of the stamens. To measure the motion of the stamens to compare with our model, we analysed individual frames of a video taken at 10 000 fps. 3 The thecae of adjacent stamens dehisce in bud so that the stomia face each other, retaining pollen between neighbouring anthers. As the flowers open, pollen is accelerated vertically as long as the thecae remain in contact. Pollen is released only when the anthers move horizontally and separate. 4 The observed motion of the stamens matches the results from our model through release of the pollen. The model reveals that pollen release (horizontal movement of the anthers) occurs only after the vertical speed is at its maximum. Thus, for this particular catapult mechanism, the morphology of the stamens is optimal for launching light, dry pollen straight upwards at high speed. Pollen launched vertically at high speed both enhances insect pollination by helping to making pollen stick on visiting insects, and also allows for successful wind pollination by propelling pollen into the air column. Seed set by inflorescences in pollinator-exclosure cages further supports the ability of this flower to use wind as a pollination mechanism.

Functional Ecology

9066035

10.1529/BIOPHYSJ.107.128389

Cartilage aggrecan can undergo self-adhesion.

Here it is reported that aggrecan, the highly negatively charged macromolecule in the cartilage extracellular matrix, undergoes Ca(2+)-mediated self-adhesion after static compression even in the presence of strong electrostatic repulsion in physiological-like solution conditions. Aggrecan was chemically end-attached onto gold-coated planar silicon substrates and gold-coated microspherical atomic force microscope probe tips (end radius R approximately 2.5 mum) at a density ( approximately 40 mg/mL) that simulates physiological conditions in the tissue ( approximately 20-80 mg/mL). Colloidal force spectroscopy was employed to measure the adhesion between opposing aggrecan monolayers in NaCl (0.001-1.0 M) and NaCl + CaCl(2) ([Cl(-)] = 0.15 M, [Ca(2+)] = 0 - 75 mM) aqueous electrolyte solutions. Aggrecan self-adhesion was found to increase with increasing surface equilibration time upon compression (0-30 s). Hydrogen bonding and physical entanglements between the chondroitin sulfate-glycosaminoglycan side chains are proposed as important factors contributing to aggrecan self-adhesion. Self-adhesion was found to significantly increase with decreasing bath ionic strength (and hence, electrostatic double-layer repulsion), as well as increasing Ca(2+) concentration due to the additional ion-bridging effects. It is hypothesized that aggrecan self-adhesion, and the macromolecular energy dissipation that results from this self-adhesion, could be important factors contributing to the self-assembled architecture and integrity of the cartilage extracellular matrix in vivo.

Biophysical Journal

206960570

10.1007/S00359-008-0408-1

Surface structure and frictional properties of the skin of the Amazon tree boa Corallus hortulanus (Squamata, Boidae)

The legless locomotion of snakes requires specific adaptations of their ventral scales to maintain friction force in different directions. The skin microornamentation of the snake Corallus hortulanus was studied by means of scanning electron microscopy and the friction properties of the skin were tested on substrates of different roughness. Skin samples from various parts of the body (dorsal, lateral, ventral) were compared. Dorsal and lateral scales showed similar, net-like microornamentation and similar friction coefficients. Average friction coefficients for dorsal and lateral scales on the epoxy resin surfaces were 0.331 and 0.323, respectively. In contrast, ventral scales possess ridges running parallel to the longitudinal body axis. They demonstrated a significantly lower friction coefficient compared to both dorsal and lateral scales (0.191 on average). In addition, ventral scales showed frictional anisotropy comparing longitudinal and perpendicular direction of the ridges. This study clearly demonstrates that different skin microstructure is responsible for different frictional properties in different body regions.

Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology

2821524

10.1016/J.JSB.2010.04.009

Quantitative microstructural studies of the armor of the marine threespine stickleback (Gasterosteus aculeatus).

In this study, a quantitative investigation of the microstructure and composition of field-caught marine Gasterosteus aculeatus (threespine stickleback) armor is presented, which provides useful phylogenetic information and insights into biomechanical function. Micro-computed tomography (microCT) was employed to create full three-dimensional images of the dorsal spines and basal plate, lateral plates, pelvic girdle and spines and to assess structural and compositional properties such as the spatial distribution of thickness (approximately 100-300 microm), the heterogeneous cross-sectional geometry (centrally thickened), plate-to-plate juncture and overlap (approximately 50% of the plate width), and bone mineral density (634-748 HA/cm(3)). The convolution of plate geometry in conjunction with plate-to-plate overlap allows a relatively constant armor thickness to be maintained throughout the assembly, promoting spatially homogeneous protection and thereby avoiding weakness at the armor unit interconnections. Plate-to-plate junctures act to register and join the plates while permitting compliance in sliding and rotation in selected directions. Mercury porosimetry was used to determine the pore size distribution and volume percent porosity of the lateral plates (20-35 vol.%) and spines (10-15 vol.%). SEM and microCT revealed a porous, sandwich-like cross-section beneficial for bending stiffness and strength at minimum weight. Back-scattered electron microscopy and energy dispersive X-ray analysis were utilized to quantify the weight percent mineral content (58-68%). Scanning electron microscopy and surface profilometry were used to characterize the interior and exterior surface topography (tubercles) of the lateral plates. The results obtained in this study are discussed in the context of mechanical function, performance, fitness, and survivability.

Journal of Structural Biology

18700240

10.1073/PNAS.0911223107

Foldable structures and the natural design of pollen grains

Upon release from the anther, pollen grains of angiosperm flowers are exposed to a dry environment and dehydrate. To survive this process, pollen grains possess a variety of physiological and structural adaptations. Perhaps the most striking of these adaptations is the ability of the pollen wall to fold onto itself to prevent further desiccation. Roger P. Wodehouse coined the term harmomegathy for this folding process in recognition of the critical role it plays in the survival of the pollen grain. There is still, however, no quantitative theory that explains how the structure of the pollen wall contributes to harmomegathy. Here we demonstrate that simple geometrical and mechanical principles explain how wall structure guides pollen grains toward distinct folding pathways. We found that the presence of axially elongated apertures of high compliance is critical for achieving a predictable and reversible folding pattern. Moreover, the intricate sculpturing of the wall assists pollen closure by preventing mirror buckling of the surface. These results constitute quantitative structure-function relationships for pollen harmomegathy and provide a framework to elucidate the functional significance of the very diverse pollen morphologies observed in angiosperms.

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

11729140

10.1016/J.JPAINSYMMAN.2004.01.007

Aggressive pharmacological treatment for reversing malignant bowel obstruction.

Early and intensive pharmacological treatment not only may reduce gastrointestinal symptoms but also reverse malignant bowel obstruction. Fifteen consecutive advanced cancer patients with inoperable bowel obstruction received a combination of drugs including metoclopramide, octreotide, dexamethasone and an initial bolus of amidotrizoato. Recovery of intestinal transit was reported within 1-5 days in fourteen patients, who continued this treatment without presenting symptoms of bowel obstruction until death. This case series establishes that the combination of propulsive and antisecretive agents can act synergistically to allow a fast recovery of bowel transit without inducing unpleasant colic. It suggests that the most important mechanism in these circumstances is functional and can be reversible, if an aggressive treatment is initiated early before fecal impaction and edema render bowel obstruction irreversible.

Journal of Pain and Symptom Management

5954241

10.1021/LA203942R

Erosion resistance of bionic functional surfaces inspired from desert scorpions.

In this paper, a bionic method is presented to improve the erosion resistance of machine components. Desert scorpion (Androctonus australis) is a typical animal living in sandy deserts, and may face erosive action of blowing sand at a high speed. Based on the idea of bionics and biologic experimental techniques, the mechanisms of the sand erosion resistance of desert scorpion were investigated. Results showed that the desert scorpions used special microtextures such as bumps and grooves to construct the functional surfaces to achieve the erosion resistance. In order to understand the erosion resistance mechanisms of such functional surfaces, the combination of computational and experimental research were carried out in this paper. The Computational Fluid Dynamics (CFD) method was applied to predict the erosion performance of the bionic functional surfaces. The result demonstrated that the microtextured surfaces exhibited better erosion resistance than the smooth surfaces. The further erosion tests indicated that the groove surfaces exhibited better erosion performance at 30° injection angle. In order to determine the effect of the groove dimensions on the erosion resistance, regression analysis of orthogonal multinomials was also performed under a certain erosion condition, and the regression equation between the erosion rate and groove distance, width, and height was established.

Langmuir

12046551

10.1007/S10811-010-9505-Y

Carotenoid fluorescence in Dunaliella salina

Dunaliella salina is a halotolerant green alga that is well known for its carotenoid producing capacity. The produced carotenoids are mainly stored in lipid globules. For various research purposes, such as production and extraction kinetics, we would like to determine and/or localise the carotenoid globules in vivo. In this study, we show that the carotenoid-rich globules emit clear green fluorescence, which can be used in, for example, fluorescence microscopy (e.g. CLSM) to obtain pictures of the cells and their carotenoid content.

Journal of Applied Phycology

206521539

10.1126/SCIENCE.1177055

The Molecular Basis of Nacre Formation

A protein complex guides the process of nacre formation in mollusk shells. The mechanisms that determine the structural features of organisms are complex, and we are still far from predicting the structure of an organism by looking at its genetic makeup. An additional level of complexity exists for organisms that form body parts composed of mineralized structures such as sea shells, bone, and teeth. These organisms must also carefully control the interfaces between the soft body parts and the growing mineral. On page 1388 in this issue, Suzuki et al. (1) identify two novel proteins, Pif80 and Pif97, as key players in controlling the crystal structure of calcium carbonate (CaCO3) in the pearl-forming oyster Pinctada fucata. The work provides the most complete data set to date for the role of any known protein involved in mollusk biomineralization. The methods used in this study may be widely applied in future studies in this field.

Science

8243789

10.1021/BI00505A018

Earthworm bioluminescence: characterization of high specific activity Diplocardia longa luciferase and the reaction it catalyzes.

Diplocardia longa luciferase purified by an improved procedure differs from that first described by Bellisario et al. [Bellisario, R., Spencer, T. E., & Cormier, M. J. (1972) Biochemistry 11, 2256-2266] in having much higher specific activity (40X) and firmly bound, EPR-silent copper. Improved assay conditions suggest that this protein acts as a catalyst in a bioluminescent reaction involving the degradation of 3-(isovalerylamino)-1-hydroxypropane hydroperoxide. This substrate is formed spontaneously on the addition of hydrogen peroxide to D. longa luciferin (3-(isovalerylamino)propanal). The quantum yield of the bioluminescence for this substrate is 3%. Detailed physical and chemical analyses of high specific activity D. longa luciferase indicate that it is a large (300000 daltons), asymmetric (f/fo=1.63, with 0.4 g/g hydration), multisubunit enzyme. It contains carbohydrate (6%), lipid (2%), and copper (up to 4 mol/30000 daltons). The amino acid composition is unusual with 11% by weight of the residues being either proline or hydroxyproline.

Biochemistry

24905817

10.1146/ANNUREV-ENTO-112408-085338

Feeding mechanisms of adult Lepidoptera: structure, function, and evolution of the mouthparts.

The form and function of the mouthparts in adult Lepidoptera and their feeding behavior are reviewed from evolutionary and ecological points of view. The formation of the suctorial proboscis encompasses a fluid-tight food tube, special linking structures, modified sensory equipment, and novel intrinsic musculature. The evolution of these functionally important traits can be reconstructed within the Lepidoptera. The proboscis movements are explained by a hydraulic mechanism for uncoiling, whereas recoiling is governed by the intrinsic proboscis musculature and the cuticular elasticity. Fluid uptake is accomplished by the action of the cranial sucking pump, which enables uptake of a wide range of fluid quantities from different food sources. Nectar-feeding species exhibit stereotypical proboscis movements during flower handling. Behavioral modifications and derived proboscis morphology are often associated with specialized feeding preferences or an obligatory switch to alternative food sources.

Annual Review of Entomology

3059796

10.1085/JGP.40.2.201

THE RESPONSES OF THE PUPIL OF GEKKO GEKKO TO EXTERNAL LIGHT STIMULUS

1. The responses of the pupil of a nocturnal gecko (Gekko gekko) to external light stimulus were studied. 2. The responses of the pupil are determined by light entering the pupil and not by light acting directly on the iris. 3. The responses of the pupil are very uniform in sensitivity including spectral sensitivity for light coming in different directions to the eye. 4. The possible change in area of the pupil is more than 300-fold and probably represents an effort to shield the pure rod retina from saturating light intensities. 5. The pupil continues to contract sharply for changes in external light intensity which give retinal illuminations corresponding to 106 quanta/sec. striking a retinal rod. 6. There is a large degree of spatial summation of the response; circular external light fields subtending 5 and 140° giving the same illumination at the pupil give approximately the same pupil response. 7. The spectral sensitivity curve agrees with the absorption curve of an extracted pigment from a closely related gecko described by Crescitelli in the followig paper. It is similar to the human scotopic curve but its maximum is displaced about 20 to 30 mµ towards the red end of the spectrum. The fall in sensitivity towards the red end of the spectrum is described by the equation See PDF for Equation

The Journal of General Physiology

5519621

10.1073/PNAS.1006943108

Iron conservation by reduction of metalloenzyme inventories in the marine diazotroph Crocosphaera watsonii

The marine nitrogen fixing microorganisms (diazotrophs) are a major source of nitrogen to open ocean ecosystems and are predicted to be limited by iron in most marine environments. Here we use global and targeted proteomic analyses on a key unicellular marine diazotroph Crocosphaera watsonii to reveal large scale diel changes in its proteome, including substantial variations in concentrations of iron metalloproteins involved in nitrogen fixation and photosynthesis, as well as nocturnal flavodoxin production. The daily synthesis and degradation of enzymes in coordination with their utilization results in a lowered cellular metalloenzyme inventory that requires ∼40% less iron than if these enzymes were maintained throughout the diel cycle. This strategy is energetically expensive, but appears to serve as an important adaptation for confronting the iron scarcity of the open oceans. A global numerical model of ocean circulation, biogeochemistry and ecosystems suggests that Crocosphaera’s ability to reduce its iron-metalloenzyme inventory provides two advantages: It allows Crocosphaera to inhabit regions lower in iron and allows the same iron supply to support higher Crocosphaera biomass and nitrogen fixation than if they did not have this reduced iron requirement.

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

12840235

10.1242/JEB.046706

The mechanics of the adhesive locomotion of terrestrial gastropods

SUMMARY Research on the adhesive locomotion of terrestrial gastropods is gaining renewed interest as it provides a source of guidance for the design of soft biomimetic robots that can perform functions currently not achievable by conventional rigid vehicles. The locomotion of terrestrial gastropods is driven by a train of periodic muscle contractions (pedal waves) and relaxations (interwaves) that propagate from their tails to their heads. These ventral waves interact with a thin layer of mucus secreted by the animal that transmits propulsive forces to the ground. The exact mechanism by which these propulsive forces are generated is still a matter of controversy. Specifically, the exact role played by the complex rheological and adhesive properties of the mucus is not clear. To provide quantitative data that could shed light on this question, we use a newly developed technique to measure, with high temporal and spatial resolution, the propulsive forces that terrestrial gastropods generate while crawling on smooth flat surfaces. The traction force measurements demonstrate the importance of the finite yield stress of the mucus in generating thrust and are consistent with the surface of the ventral foot being lifted with the passage of each pedal wave. We also show that a forward propulsive force is generated beneath each stationary interwave and that this net forward component is balanced by the resistance caused by the outer rim of the ventral foot, which slides at the speed of the center of mass of the animal. Simultaneously, the animal pulls the rim laterally inward. Analysis of the traction forces reveals that the kinematics of the pedal waves is far more complex than previously thought, showing significant spatial variation (acceleration/deceleration) as the waves move from the tail to the head of the animal.

The Journal of Experimental Biology

4412631

10.1038/435164A

Botany: A record-breaking pollen catapult

The release of stored elastic energy often drives rapid movements in animal systems, and plant components employing this mechanism should be able to move with similar speed. Here we describe how the flower stamens of the bunchberry dogwood (Cornus canadensis) rely on this principle to catapult pollen into the air as the flower opens explosively. Our high-speed video observations show that the flower opens in less than 0.5 ms — to our knowledge, the fastest movement so far recorded in a plant.

Nature

4181711

10.1242/JEB.002725

Absence of eye shine and tapetum in the heterogeneous eye of Anthocharis butterflies (Pieridae)

SUMMARY Insect eyes are composed of spectrally heterogeneous ommatidia, typically with three different types. The ommatidial heterogeneity in butterflies can be identified non-invasively by the colorful eye shine, the reflection from the tapetal mirror located at the proximal end of the ommatidia, which can be observed by epi-illumination microscopy. Since the color of eye shine is determined by the spectral properties of the ommatidia, it has been tentatively related to color vision. In the course of a survey of ommatidial heterogeneity in butterflies, we found that members of the pierid genus Anthocharis lack the eye shine. We therefore carried out anatomy of the eye of the yellow tip, Anthocharis scolymus, and correlated it with the absence of the tapetum. The butterfly tapetum is a remnant of the ancestral moth tapetum, a trait that has been completely lost in the papilionids and also, as now appears, in the genus Anthocharis. Anatomical investigations also revealed that, considering rhabdom shape, peri-rhabdomal pigment clusters and autofluorescence, the ommatidia can be divided in at least two different types, which are randomly distributed in the retina.

The Journal of Experimental Biology

7568626

10.1073/PNAS.1415502112

New functional insights into the internal architecture of the laminated anchor spicules of Euplectella aspergillum

Significance The remarkable properties of biological structural materials can often be attributed to the composite arrangement of their constituents. This paper focuses on the high-aspect-ratio, load-bearing, glassy skeletal fibers (spicules) of the marine sponge Euplectella aspergillum. Considering that the spicules’ internal architecture cannot be repaired or remodeled, we hypothesize that there is a connection between their internal structure and their strength. Using a newly developed structural mechanics model for composite beams, we demonstrate that the unique internal geometry that maximizes a beam’s strength correlates well with the geometry observed in the native spicules. This bio-inspired design strategy for increasing a beam's strength has implications for a new generation of man-made structural materials. To adapt to a wide range of physically demanding environmental conditions, biological systems have evolved a diverse variety of robust skeletal architectures. One such example, Euplectella aspergillum, is a sediment-dwelling marine sponge that is anchored into the sea floor by a flexible holdfast apparatus consisting of thousands of anchor spicules (long, hair-like glassy fibers). Each spicule is covered with recurved barbs and has an internal architecture consisting of a solid core of silica surrounded by an assembly of coaxial silica cylinders, each of which is separated by a thin organic layer. The thickness of each silica cylinder progressively decreases from the spicule’s core to its periphery, which we hypothesize is an adaptation for redistributing internal stresses, thus increasing the overall strength of each spicule. To evaluate this hypothesis, we created a spicule structural mechanics model, in which we fixed the radii of the silica cylinders such that the force transmitted from the surface barbs to the remainder of the skeletal system was maximized. Compared with measurements of these parameters in the native sponge spicules, our modeling results correlate remarkably well, highlighting the beneficial nature of this elastically heterogeneous lamellar design strategy. The structural principles obtained from this study thus provide potential design insights for the fabrication of high-strength beams for load-bearing applications through the modification of their internal architecture, rather than their external geometry.

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

11991246

10.1002/CHEM.200600825

In vitro study of magnesium-calcite biomineralization in the skeletal materials of the seastar Pisaster giganteus.

The mechanisms of formation of biogenic magnesium-rich calcite remain an enigma. Here we present ultrastructural and compositional details of ossicles from the seastar Pisaster giganteus (Echinodermata, Asteroidea). Powder X-ray diffraction, infrared spectroscopy and elemental analyses confirm that the ossicles are composed of magnesium-rich calcite, whilst also containing about 0.01 % (w/w) of soluble organic matrix (SOM) as an intracrystalline component. Amino acid analysis and N-terminal sequencing revealed that this mixture of intracrystalline macromolecules consists predominantly of glycine-rich polypeptides. In vitro calcium carbonate precipitation experiments indicate that the SOM accelerates the conversion of amorphous calcium carbonate (ACC) into its final crystalline product. From this observation and from the discovery of ACC in other closely related taxa, it is suggested that substitution of magnesium into the calcite lattice through a transient precursor phase may be a universal phenomenon prevalent across the phylum echinodermata.

Chemistry: A European Journal

17807631

10.1121/1.421291

The mammalian auditory hair cell: a simple electric circuit model.

A model based on the potassium current pathway through the hair cell is used to analyze the electrical behavior of mammalian inner and outer hair cells. Without taking into account the effects of calcium it is possible to simulate experimental results concerning the shape and strength of the receptor potential and the frequency dependent ac (alternating current) and dc (direct current) components of the receptor current. This model and a simplified form of it are utilized to explain: (1) Transduction latencies: that the receptor potential follows a stimulating signal with a very short delay, under the assumption of a constant number of open K+ channels in the lateral part of the cell membrane. (2) Transduction gains: why higher potential changes are measured in inner hair cells than in outer hair cells, although the outer hair cells are expected to be exposed to higher stereociliary motions: in inner hair cells a decrease in the conductance of the basolateral membrane causes higher gain (receptor potential increases) and together with an increase of membrane capacitance slower reaction (a larger time constant). (3) Transduction channel kinetics: that the shortest (0.1 ms) as well as the longest (20 ms) possible open times of the transduction channels in the stereocilia have different frequency related effects on the shape of the receptor potentials.

Journal of the Acoustical Society of America

5736224

10.1098/RSBL.2005.0322

Ultraviolet reflecting photonic microstructures in the King Penguin beak

King and emperor penguins (Aptenodytes patagonicus and Aptenodytes forsteri) are the only species of marine birds so far known to reflect ultraviolet (UV) light from their beaks. Unlike humans, most birds perceive UV light and several species communicate using the near UV spectrum. Indeed, UV reflectance in addition to the colour of songbird feathers has been recognized as an important signal when choosing a mate. The king penguin is endowed with several highly coloured ornaments, notably its beak horn and breast and auricular plumage, but only its beak reflects UV, a property considered to influence its sexual attraction. Because no avian UV-reflecting pigments have yet been identified, the origin of such reflections is probably structural. In an attempt to identify the structures that give rise to UV reflectance, we combined reflectance spectrophotometry and morphological analysis by both light and electron microscopy, after experimental removal of surface layers of the beak horn. Here, we characterize for the first time a multilayer reflector photonic microstructure that produces the UV reflections in the king penguin beak.

Biology Letters

55659106

10.3354/MEPS207227

Geographic variation in halogenated furanones from the red alga Delisea pulchra and associated herbivores and epiphytes

We examine patterns of quantitative variation in halogenated furanones, secondary metabolites of Delisea pulchra (Rhodophyta; Bonnemaisoniales), and how this relates to variation in local abundance of herbivores and epiphytes. Fifteen populations of D. pulchra covering a distance of 650 km of temperate southeastern Australia were sampled. Concentrations of the 4 main furanones in D. pulchra (Compounds 1 to 4) showed large variability but there was no latitudinal trend to this variation. We found significant variation in the concentrations of both total and individual furanones among locations, between summer and winter, and between different life-history stages. Importantly, the range of total furanone concentration among plants within locations was large, often varying by an order of magnitude or more. A total of 5 species of herbivorous fish, 7 species of macroinvertebrate grazer and 6 groups of mesograzer (of varying taxonomic level) were found at the 15 locations. The abundance of both total macroinvertebrate grazers and total mesograzers known to consume D. pul- chra varied significantly among locations. However, correlations between furanones and the abun- dance of macroinvertebrate grazers and mesograzers at the scale of location were all weak and non- significant, as was the correlation between furanones and the abundance of epiphytes on D. pulchra. The large variability in concentrations of furanones, and the absence of any positive relationships between furanones, herbivores and epiphytes, suggest that quantitative variation in furanones in D. pulchra is not driven by population-level selection or induction, but is more likely to be a result of small-scale variation in environmental factors such as nutrients and light, and genetic differences among individual plants.

Marine Ecology Progress Series

23366820

10.1007/S00114-003-0495-3

The eyes of oilbirds (Steatornis caripensis): pushing at the limits of sensitivity

An extreme example of a low light-level lifestyle among flying birds is provided by the oilbird, Steatornis caripensis (Steatornithidae, Caprimulgiformes). Oilbirds breed and roost in caves, often at sufficient depth that no daylight can penetrate, and forage for fruits at night. Using standard microscopy techniques we investigated the retinal structure of oilbird eyes and used an ophthalmoscopic reflex technique to determine the parameters of these birds’ visual fields. The retina is dominated by small rod receptors (diameter 1.3±0.2 μm; length 18.6±0.6 μm) arranged in a banked structure that is unique among terrestrial vertebrates. This arrangement achieves a photoreceptor density that is the highest so far recorded (≈1,000,000 rods mm−2) in any vertebrate eye. Cone photoreceptors are, however, present in low numbers. The eye is relatively small (axial length 16.1±0.2 mm) with a maximum pupil diameter of 9.0±0.0 mm, achieving a light-gathering capacity that is the highest recorded in a bird (f-number ≈1.07). The binocular field has a maximum width of 38° and extends vertically through 100° with the bill projecting towards the lower periphery; a topography that suggests that vision is not used to control bill position. We propose that oilbird eyes are at one end of the continuum that juxtaposes the conflicting fundamental visual capacities of sensitivity and resolution. Thus, while oilbird visual sensitivity may be close to a maximum, visual resolution must be low. This explains why these birds employ other sensory cues, including olfaction and echolocation, in the control of their behaviour in low-light-level environments.

Naturwissenschaften

5028096

10.1098/RSIF.2010.0201

Function of blue iridescence in tropical understorey plants

The blue colouration seen in the leaves of Selaginella willdenowii is shown to be iridescent. Transmission electron microscopy studies confirm the presence of a layered lamellar structure of the upper cuticle of iridescent leaves. Modelling of these multi-layer structures suggests that they are responsible for the blue iridescence, confirming the link between the observed lamellae and the recorded optical properties. Comparison of blue and green leaves from the same plant indicates that the loss of the blue iridescence corresponds to a loss of the multi-layer structure. The results reported here do not support the idea that iridescence in plants acts to enhance light capture of photosynthetically important wavelengths. The reflectance of light in the range 600–700 nm is very similar for both iridescent and non-iridescent leaves. However, owing to the occurrence of blue colouration in a wide variety of shade dwelling plants it is probable that this iridescence has some adaptive benefit. Possible adaptive advantages of the blue iridescence in these plants are discussed.

Journal of the Royal Society Interface

16399463

10.1371/JOURNAL.PBIO.1000469

Precise Temperature Compensation of Phase in a Rhythmic Motor Pattern

Computational modeling and experimentation in a model system for network dynamics reveal how network phase relationships are temperature-compensated in terms of their underlying synaptic and intrinsic membrane currents.

PLOS Biology

10897119

10.1093/MOLBEV/MSM171

Conservation of essential design features in coiled coil silks.

Silks are strong protein fibers produced by a broad array of spiders and insects. The vast majority of known silks are large, repetitive proteins assembled into extended beta-sheet structures. Honeybees, however, have found a radically different evolutionary solution to the need for a building material. The 4 fibrous proteins of honeybee silk are small ( approximately 30 kDa each) and nonrepetitive and adopt a coiled coil structure. We examined silks from the 3 superfamilies of the Aculeata (Hymenoptera: Apocrita) by infrared spectroscopy and found coiled coil structure in bees (Apoidea) and in ants (Vespoidea) but not in parasitic wasps of the Chrysidoidea. We subsequently identified and sequenced the silk genes of bumblebees, bulldog ants, and weaver ants and compared these with honeybee silk genes. Each species produced orthologues of the 4 small fibroin proteins identified in honeybee silk. Each fibroin contained a continuous predicted coiled coil region of around 210 residues, flanked by 23-160 residue length N- and C-termini. The cores of the coiled coils were unusually rich in alanine. There was extensive sequence divergence among the bee and ant silk genes (<50% similarity between the alignable regions of bee and ant sequences), consistent with constant and equivalent divergence since the bee/ant split (estimated to be 155 Myr). Despite a high background level of sequence diversity, we have identified conserved design elements that we propose are essential to the assembly and function of coiled coil silks.

Molecular Biology and Evolution

45995550

10.1073/PNAS.97.12.6568

Defense by foot adhesion in a beetle (Hemisphaerota cyanea).

The beetle Hemisphaerota cyanea (Chrysomelidae; Cassidinae) responds to disturbance by activating a tarsal adhesion mechanism by which it secures a hold on the substrate. Its tarsi are oversized and collectively bear some 60,000 adhesive bristles, each with two terminal pads. While walking, the beetle commits but a small fraction of the bristles to contact with the substrate. But when assaulted, it presses its tarsi flatly down, thereby touching ground with all or nearly all of the bristles. Once so adhered, it can withstand pulling forces of up to 0.8 g ( approximately 60 times its body mass) for 2 min, and of higher magnitudes, up to >3 g, for shorter periods. Adhesion is secured by a liquid, most probably an oil. By adhering, the beetle is able to thwart attacking ants, given that it is able to cling more persistently than the ant persists in its assault. One predator, the reduviid Arilus cristatus, is able to feed on the beetle, possibly because by injecting venom it prevents the beetle from maintaining its tarsal hold.

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

7834092

10.1098/RSIF.2010.0722

From three-dimensional weavings to swollen corneocytes

A novel technique to generate three-dimensional Euclidean weavings, composed of close-packed, periodic arrays of one-dimensional fibres, is described. Some of these weavings are shown to dilate by simple shape changes of the constituent fibres (such as fibre straightening). The free volume within a chiral cubic example of a dilatant weaving, the ideal conformation of the G129 weaving related to the Σ+ rod packing, expands more than fivefold on filament straightening. This remarkable three-dimensional weaving, therefore, allows an unprecedented variation of packing density without loss of structural rigidity and is an attractive design target for materials. We propose that the G129 weaving (ideal Σ+ weaving) is formed by keratin fibres in the outermost layer of mammalian skin, probably templated by a folded membrane.

Journal of the Royal Society Interface

18832578

10.1371/JOURNAL.PCBI.1002177

Smart Swarms of Bacteria-Inspired Agents with Performance Adaptable Interactions

Collective navigation and swarming have been studied in animal groups, such as fish schools, bird flocks, bacteria, and slime molds. Computer modeling has shown that collective behavior of simple agents can result from simple interactions between the agents, which include short range repulsion, intermediate range alignment, and long range attraction. Here we study collective navigation of bacteria-inspired smart agents in complex terrains, with adaptive interactions that depend on performance. More specifically, each agent adjusts its interactions with the other agents according to its local environment – by decreasing the peers' influence while navigating in a beneficial direction, and increasing it otherwise. We show that inclusion of such performance dependent adaptable interactions significantly improves the collective swarming performance, leading to highly efficient navigation, especially in complex terrains. Notably, to afford such adaptable interactions, each modeled agent requires only simple computational capabilities with short-term memory, which can easily be implemented in simple swarming robots.

PLOS Computational Biology

203607800

10.1016/J.TREE.2019.08.007

Resisting Antimicrobial Resistance: Lessons from Fungus Farming Ants.

Attine ants use antimicrobials produced by commensal bacteria to inhibit parasites on their fungal gardens. However, in this agricultural system, antimicrobial use does not lead to overwhelming resistance, as is typical in clinical settings. Mixtures of continually evolving antimicrobial variants could support these dynamics.

Trends in Ecology and Evolution

21573148

10.1007/S00114-009-0596-8

Orange/lemon-scented beetles: opposite enantiomers of limonene as major constituents in the defensive secretion of related carabids

The major constituent in the pygidial gland defensive fluid of the carabid beetle Ardistomis schaumii is (R)-(+)-limonene, whereas that of Semiardistomis puncticollis is (S)-(−)-limonene. This was an unanticipated result, since it is not very common to find the opposite enantiomers of the same compound among the secondary metabolites of related species. Moreover, the glandular liquid of A. schaumii contains 1,8-cineole, and that of S. puncticollis has β-pinene, β-phellandrene, sabinene, and p-cymene. Of about 500 carabid species that have been chemically investigated, this is the first report of the presence of such complex mixtures of monoterpenes in their defensive secretions.

Naturwissenschaften

780780

10.1098/RSIF.2012.0429

Wet mammals shake at tuned frequencies to dry

In cold wet weather, mammals face hypothermia if they cannot dry themselves. By rapidly oscillating their bodies, through a process similar to shivering, furry mammals can dry themselves within seconds. We use high-speed videography and fur particle tracking to characterize the shakes of 33 animals (16 animals species and five dog breeds), ranging over four orders of magnitude in mass from mice to bears. We here report the power law relationship between shaking frequency f and body mass M to be f ∼ M−0.22, which is close to our prediction of f ∼ M−0.19 based upon the balance of centrifugal and capillary forces. We also observe a novel role for loose mammalian dermal tissue: by whipping around the body, it increases the speed of drops leaving the animal and the ensuing dryness relative to tight dermal tissue.

Journal of the Royal Society Interface

4391475

10.1038/NATURE04925

Electrical signals control wound healing through phosphatidylinositol-3-OH kinase-γ and PTEN

Wound healing is essential for maintaining the integrity of multicellular organisms. In every species studied, disruption of an epithelial layer instantaneously generates endogenous electric fields, which have been proposed to be important in wound healing. The identity of signalling pathways that guide both cell migration to electric cues and electric-field-induced wound healing have not been elucidated at a genetic level. Here we show that electric fields, of a strength equal to those detected endogenously, direct cell migration during wound healing as a prime directional cue. Manipulation of endogenous wound electric fields affects wound healing in vivo. Electric stimulation triggers activation of Src and inositol–phospholipid signalling, which polarizes in the direction of cell migration. Notably, genetic disruption of phosphatidylinositol-3-OH kinase-γ (PI(3)Kγ) decreases electric-field-induced signalling and abolishes directed movements of healing epithelium in response to electric signals. Deletion of the tumour suppressor phosphatase and tensin homolog (PTEN) enhances signalling and electrotactic responses. These data identify genes essential for electrical-signal-induced wound healing and show that PI(3)Kγ and PTEN control electrotaxis.

Nature

30454029

10.1016/S0167-4838(99)00160-0

Draculin, the anticoagulant factor in vampire bat saliva, is a tight-binding, noncompetitive inhibitor of activated factor X.

The kinetic mechanism of action of Draculin on activated Factor X (FXa) is established. Draculin inhibits activated Factor X within seconds of incubation at near equimolar concentration (2-6 times on molar basis). Fitting the data to the equation for a tight-binding inhibitor gives a value for K(i)(K(d)) = 14.8+/-1.5 nM. The formation of the Draculin-FXa complex can be explained by a two-step mechanism, where for the first, reversible step, k(on) = 1.117 (+/- 0.169, S.E.M.) x 10(6) M(-1)s(-1) and k(off) = 15.388 (+/- 1.672) x 10(-3) s(-1), while for the second, irreversible step, which is concentration-independent, k(2) = 0.072 s(-1). K(d) obtained from k(off)/k(on) = 13.76 nM. Lineweaver-Burk plot shows a noncompetitive behavior. This noncompetitive mode of inhibition of Draculin is supported by the observation that Draculin, at concentrations giving complete inhibition, does not impair binding of p-aminobenzamidine to FXa. Moreover, under the same conditions, Draculin induces <14% decrease of the fluorescence intensity of the p-aminobenzamidine-FXa complex. We conclude that Draculin is a noncompetitive, tight-binding inhibitor of FXa, a characteristic so far unique amongst natural FXa inhibitors.

Biochimica et Biophysica Acta

89440265

10.1093/FORESTSCIENCE/48.3.582

A method for characterizing and mimicking forest canopy gaps caused by different disturbances

Forest canopy gaps are measurable indicators of past small-scale disturbances. These disturbances can impact forest stand dynamics in ways that help maintain and enhance many ecosystem values. Impacts are commonly assessed using timber production metrics based on average stand values, but metrics based on smaller scales are needed to assess impacts on nontimber resources. In this study, we developed a multivariate method of quantitatively characterizing individual canopy gaps in Douglas-fir/grand fir stands in the Blue Mountains of eastern Oregon. We then established a reference or target range of variability by profiling gaps according to numbers of snags, downed logs, gap size and shape, and recolonizing vegetation. Cluster analysis, multidimensional scaling, and classification trees were used with these profiles to quantify similarity among individual gaps. Gaps fell into four groups, which could be interpreted as three ecologically functional groups on the basis of their role in stand development. Gaps caused by the same agents commonly fell within the same functional group: (1) flooding, logging, spruce budworm, and windfall cause stand level impacts that reset the stand development sequence; (2) bark beetles, tree fall, and root diseases cause within stand impacts that altered the rate of stand development; and (3) stem decay and dwarf mistletoe, and, under some circumstances, all disturbance agents, could kill trees yet have no impact on stand development except create space into which neighboring trees expand. We present a simple test to monitor how gaps change with silvicultural manipulations. Results indicate that this method offers (1) a way to systematically guide silvicultural manipulations aimed at mimicking natural disturbances at the canopy gap scale, and (2) a way to monitor the effectiveness of such silvicultural treatments and management actions using gap-based silviculture prescriptions.

Forest Science

36718346

10.1016/J.ACTBIO.2010.02.009

Hardness in arthropod exoskeletons in the absence of transition metals.

The arthropod cuticle is a remarkable and versatile biological material commonly composed of chitin and proteins. Lessons can be learned from the way it is adapted to fit its functions. The larval jewel beetle, Pseudotaenia frenchi, demonstrates hardness in the cutting edge of the mandibles in excess of the mineralized carapace of stone crabs and compares favourably with some stainless steels. Yet this is a form of cuticle which is devoid of transition metals or mineralization. In seeming contradiction, the similarly dark coloured adult beetle mandibles contain the transition metal manganese, but are significantly softer. Energy dispersive X-ray analysis and infrared spectroscopy have been used to investigate the differences in composition of mandible cuticle of the adult and larval beetles.

Acta Biomaterialia

8527127

10.1126/SCIENCE.1204245

A Biological Screw in a Beetle’s Leg

Joints on the legs of weevils form a functional screw-and-nut system. The coxa-trochanteral joints on the legs of the weevil Trigonopterus oblongus (Pascoe) work as a biological screw-and-nut system. The apical portions of the coxae closely resemble nuts with well-defined inner threads covering 345°. The corresponding trochanters have perfectly compatible external spiral threads of 410°.

Science

4268751

10.1038/247074A0

Calcium Carbonate in Termite Mounds

THE presence of appreciable quantities of calcium carbonate in termite mounds on non-calcareous soil has intrigued pedologists for many years. Milne6, for example, found a termite mound with 7% calcium carbonate and estimated that it contained about 2 t of calcium carbonate excluding the hard limestone (53% CaCO3) base of the mound. The soil below the base of a termite mound may also be calcareous. The soil underneath one termite mound in an area of non-calcareous soil was found to have a mean of 1.7% calcium carbonate to a depth of 6 m, or about 20 t of calcium carbonate9.

Nature

15064135

10.1073/PNAS.1007808108

Growth, geometry, and mechanics of a blooming lily

Despite the common use of the blooming metaphor, its floral inspiration remains poorly understood. Here we study the physical process of blooming in the asiatic lily Lilium casablanca. Our observations show that the edges of the petals wrinkle as the flower opens, suggesting that differential growth drives the deployment of these laminar shell-like structures. We use a combination of surgical manipulations and quantitative measurements to confirm this hypothesis and provide a simple theory for this change in the shape of a doubly curved thin elastic shell subject to differential growth across its planform. Our experiments and theory overturn previous hypotheses that suggest that blooming is driven by differential growth of the inner layer of the petals and in the midrib by providing a qualitatively different paradigm that highlights the role of edge growth. This functional morphology suggests new biomimetic designs for deployable structures using boundary or edge actuation rather than the usual bulk or surface actuation.

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

33315900

10.1002/(SICI)1097-010X(19980815)281:6<582::AID-JEZ6>3.0.CO;2-J

Frequency specificity of vibration dependent discharge of nematocysts in sea anemones.

Hair bundles on tentacles of sea anemones are similar to vertebrate hair bundles in terms of structure and function. Anemone hair bundles are involved in regulating discharge of nematocysts, "stinging capsules," used to capture prey. N-acetylated sugars from the prey including N-acetylneuraminic acid (NANA) induce hair bundles to elongate while shifting vibration dependent discharge of nematocysts to lower frequencies matching prey movements. In the present study, we find that vibration dependent discharge of nematocysts exhibits sharp frequency discrimination to within one Hz. Testing at one-Hz intervals over the range of frequencies spanning 1-75 Hz, we find that seven of these are stimulatory in seawater alone. A total of twenty-six frequencies are stimulatory in the presence of NANA. Stimulatory frequencies in NANA are lower than those in seawater alone. We find that antagonists of ryanodine receptors including ryanodine, procaine and tetracaine shift discharge to lower frequencies. Fluorescently tagged ryanodine labels numerous small loci in the apical cytoplasm of supporting cells. We propose that calcium induced calcium release (CICR) via ryanodine receptors may sharpen frequency specificity and/or cause shortening of hair bundles to shift frequency specificity to higher frequencies.

Journal of Experimental Zoology

2307873

10.2307/1542126

Sag-Mediated Modulated Tension in Terebellid Tentacles Exposed to Flow.

The long, compliant feeding tentacles of the terebellid polychaete Eupolymnia heterobranchia not only stretch out over a sandflat substratum but also extend into flow. Tentacles suspended perpendicular to flow responded to increasing velocity by increasing their sag. An analysis of tension in these tentacles, mathematically analogous to that applicable to suspension bridges, shows that sagging permits the tentacles to avoid increases in tension that would otherwise occur as flow increases. Force modulation was achieved by active muscular control rather than by passive material properties. Although these tentacles would certainly break in the experimental flows if they did not sag, the low tension achieved suggests that some other reason, such as limitations on the adherence of cilia and mucus, accounts for the level of tension observed. Because drag is maximum on tentacles oriented perpendicular to flow, reorientation of tentacles, either by sagging or by dangling parallel to flow, additionally reduces tension by reducing drag. Theoretical estimates of drag on tentacles oriented parallel to flow show that they are never in danger of being broken. Drag is sufficient, however, to assist in passive extension of tentacles. While reorientation is a common mode of drag reduction among marine organisms, sagging represents a novel mechanism of mediating structural forces resulting from flow.

The Biological Bulletin

15066877

10.1093/ICB/42.6.1127

Structural Design and Biomechanics of Friction-Based Releasable Attachment Devices in Insects1

Abstract Design of attachment devices in insects varies enormously in relation to different functional loads. Many systems, located on different parts of the body, involve surfaces with particular frictional properties. Such systems evolved to attach parts of the body to each other, or to attach an insect to the substratum by providing fast and reversible attachment/detachment. Among these systems, there are some that deal with predefined surfaces, and others, in which one surface remains unpredictable. The first type of system occurs, for example, in wing-locking devices and head-arresting systems and is called probabilistic fasteners. The second type is mainly represented by insect attachment pads of two alternative designs: hairy and smooth. The relationship between surface patterns and/or mechanical properties of materials of contact pairs results in two main working principles of the frictional devices: mechanical interlocking, or maximization of the contact area. We give an overview of the functional design of two main groups of friction-based attachment devices in insects: probabilistic fasteners and attachment pads.

Integrative and Comparative Biology

15031876

10.1242/JEB.00764

Dynamics of leg muscle function in tammar wallabies (M. eugenii) during level versus incline hopping

SUMMARY The goal of our study was to examine whether the in vivo force-length behavior, work and elastic energy savings of distal muscle-tendon units in the legs of tammar wallabies (Macropus eugenii) change during level versus incline hopping. To address this question, we obtained measurements of muscle activation (via electromyography), fascicle strain (via sonomicrometry) and muscle-tendon force (via tendon buckles) from the lateral gastrocnemius (LG) and plantaris (PL) muscles of tammar wallabies trained to hop on a level and an inclined (10°, 17.4% grade) treadmill at two speeds (3.3 m s-1 and 4.2 m s-1). Similar patterns of muscle activation, force and fascicle strain were observed under both level and incline conditions. This also corresponded to similar patterns of limb timing and movement (duty factor, limb contact time and hopping frequency). During both level and incline hopping, the LG and PL exhibited patterns of fascicle stretch and shortening that yielded low levels of net fascicle strain [LG: level, -1.0±4.6% (mean ± s.e.m.) vs incline, 0.6±4.5%; PL: level, 0.1±1.0% vs incline, 0.4±1.6%] and muscle work (LG: level, -8.4±8.4 J kg-1 muscle vs incline, -6.8±7.5 J kg-1 muscle; PL: level, -2.0±0.6 J kg-1 muscle vs incline, -1.4±0.7 J kg-1 muscle). Consequently, neither muscle significantly altered its contractile dynamics to do more work during incline hopping. Whereas electromyographic (EMG) phase, duration and intensity did not differ for the LG, the PL exhibited shorter but more intense periods of activation, together with reduced EMG phase (P<0.01), during incline versus level hopping. Our results indicate that design for spring-like tendon energy savings and economical muscle force generation is key for these two distal muscle-tendon units of the tammar wallaby, and the need to accommodate changes in work associated with level versus incline locomotion is achieved by more proximal muscles of the limb.

The Journal of Experimental Biology

15282188

10.1016/S0960-9822(00)00764-8

Bacterial motility: How do pili pull?

Forceful retraction of a bacterial pilus has been directly observed for the first time. As retraction clarifies the basic mechanochemistry of single cell twitching and gliding movements, so cell-to-cell signalling by contact clarifies the coordination of multicellular gliding movements.

Current Biology

212460

10.1098/RSPB.2010.2292

Ultra-fast underwater suction traps

Carnivorous aquatic Utricularia species catch small prey animals using millimetre-sized underwater suction traps, which have fascinated scientists since Darwin's early work on carnivorous plants. Suction takes place after mechanical triggering and is owing to a release of stored elastic energy in the trap body accompanied by a very fast opening and closing of a trapdoor, which otherwise closes the trap entrance watertight. The exceptional trapping speed—far above human visual perception—impeded profound investigations until now. Using high-speed video imaging and special microscopy techniques, we obtained fully time-resolved recordings of the door movement. We found that this unique trapping mechanism conducts suction in less than a millisecond and therefore ranks among the fastest plant movements known. Fluid acceleration reaches very high values, leaving little chance for prey animals to escape. We discovered that the door deformation is morphologically predetermined, and actually performs a buckling/unbuckling process, including a complete trapdoor curvature inversion. This process, which we predict using dynamical simulations and simple theoretical models, is highly reproducible: the traps are autonomously repetitive as they fire spontaneously after 5–20 h and reset actively to their ready-to-catch condition.

Proceedings of The Royal Society B: Biological Sciences

130815466

10.1126/SCIENCE.1188761

Increased Food and Ecosystem Security via Perennial Grains

Perennial grains hold promise, especially for marginal landscapes or with limited resources where annual versions struggle. Despite doubling of yields of major grain crops since the 1950s, more than one in seven people suffer from malnutrition (1). Global population is growing; demand for food, especially meat, is increasing; much land most suitable for annual crops is already in use; and production of nonfood goods (e.g., biofuels) increasingly competes with food production for land (2). The best lands have soils at low or moderate risk of degradation under annual grain production but make up only 12.6% of global land area (16.5 million km2) (3). Supporting more than 50% of world population is another 43.7 million km2 of marginal lands (33.5% of global land area), at high risk of degradation under annual grain production but otherwise capable of producing crops (3). Global food security depends on annual grains—cereals, oilseeds, and legumes—planted on almost 70% of croplands, which combined supply a similar portion of human calories (4, 5). Annual grain production, though, often compromises essential ecosystem services, pushing some beyond sustainable boundaries (5). To ensure food and ecosystem security, farmers need more options to produce grains under different, generally less favorable circumstances than those under which increases in food security were achieved this past century. Development of perennial versions of important grain crops could expand options.

Science

17855598

10.1104/PP.110.156570

Molecular Mechanisms of Selenium Tolerance and Hyperaccumulation in Stanleya pinnata1[W][OA]

The molecular mechanisms responsible for selenium (Se) tolerance and hyperaccumulation were studied in the Se hyperaccumulator Stanleya pinnata (Brassicaceae) by comparing it with the related secondary Se accumulator Stanleya albescens using a combination of physiological, structural, genomic, and biochemical approaches. S. pinnata accumulated 3.6-fold more Se and was tolerant to 20 μm selenate, while S. albescens suffered reduced growth, chlorosis and necrosis, impaired photosynthesis, and high levels of reactive oxygen species. Levels of ascorbic acid, glutathione, total sulfur, and nonprotein thiols were higher in S. pinnata, suggesting that Se tolerance may in part be due to increased antioxidants and up-regulated sulfur assimilation. S. pinnata had higher selenocysteine methyltransferase protein levels and, judged from liquid chromatography-mass spectrometry, mainly accumulated the free amino acid methylselenocysteine, while S. albescens accumulated mainly the free amino acid selenocystathionine. S. albescens leaf x-ray absorption near-edge structure scans mainly detected a carbon-Se-carbon compound (presumably selenocystathionine) in addition to some selenocysteine and selenate. Thus, S. albescens may accumulate more toxic forms of Se in its leaves than S. pinnata. The species also showed different leaf Se sequestration patterns: while S. albescens showed a diffuse pattern, S. pinnata sequestered Se in localized epidermal cell clusters along leaf margins and tips, concentrated inside of epidermal cells. Transcript analyses of S. pinnata showed a constitutively higher expression of genes involved in sulfur assimilation, antioxidant activities, defense, and response to (methyl)jasmonic acid, salicylic acid, or ethylene. The levels of some of these hormones were constitutively elevated in S. pinnata compared with S. albescens, and leaf Se accumulation was slightly enhanced in both species when these hormones were supplied. Thus, defense-related phytohormones may play an important signaling role in the Se hyperaccumulation of S. pinnata, perhaps by constitutively up-regulating sulfur/Se assimilation followed by methylation of selenocysteine and the targeted sequestration of methylselenocysteine.

Plant Physiology

4172015

10.1093/ICB/ICW092

Hypoxia and Anoxia Tolerance in the Annual Killifish Austrofundulus limnaeus.

Embryos of the annual killifish Austrofundulus limnaeus are routinely exposed to oxygen limitation during development and are extremely tolerant of anoxia. Importantly, tolerance of anoxia is not strictly associated with entrance into metabolic dormancy associated with diapause II, but rather any embryo will respond to anoxia by entering into a state of anoxia-induced quiescence. Hypoxia causes a reduction in the rate of development, reduced heart rates, and reduced capacities for metabolic enzyme activity in both aerobic and anaerobic pathways. Embryos of A. limnaeus begin life as oxyconformers, and transition into oxyregulators near the completion of embryonic development. As this transition occurs, extreme anoxia tolerance is lost. The rate of early development is independent of oxygen partial pressure, despite the fact that the embryos are oxyconformers. This suggests a contribution from anaerobic pathways to support early development. However, the specific pathways supporting this metabolism are unknown. The response of A. limnaeus embryos to hypoxia and anoxia is unique compared to other fishes and most other vertebrates, and thus future studies on this species may lend insight into novel mechanisms that support survival during prolonged oxygen limitation.

Integrative and Comparative Biology

95971297

10.2136/SSSAJ2009.0313

Cutin and Cutan Biopolymers: Their Role as Natural Sorbents

The aliphatic biopolymers cutin and cutan are important precursors of soil organic matter. In this study, we examined the effects of these biopolymers' decomposition and transformation in the soil on their sorptive properties. The levels of cutin and cutan decreased by 35 and 30%, respectively, after 20 mo of incubation. Carbon-13 nuclear magnetic resonance and differential scanning calorimeter analyses suggested that the rigid (crystalline) polymethylene moieties of cutan decompose with time. This observation is in contrast to previous reports, which suggested that this alkyl-C moiety is resistant to biodegradation. Cutin, however, exhibited mainly decomposition of the mobile (amorphous) polymethylene moieties. Moreover, some of its degraded materials were transformed into humic materials. The phenanthrene sorption coefficient decreased by 80 and 37% with incubation time of the cutin and cutan samples, respectively. For 1-naphthol, the sorption capacity decreased by 90% due to cutin decomposition. With cutan, this parameter did not show any changes correlated with incubation time. Phenanthrene exhibited linear and reversible sorption isotherms. In contrast, pronounced desorption hysteresis was obtained for 1-naphthol with the 20-mo-incubated cutin sample and with all cutan samples. With all cutan samples, desorption hysteresis increased with decomposition. Our data suggest that the sorptive nature of both biopolymers was affected by soil decomposition. With degradation, the role of cutin as a natural sorbent decreases while cutan acts as a natural highly efficient sorbent for organic compounds in the soil.

Soil Science Society of America Journal

31305534

10.1128/AEM.01294-09

The Bacterially Produced Metabolite Violacein Is Associated with Survival of Amphibians Infected with a Lethal Fungus

ABSTRACT The disease chytridiomycosis, which is caused by the chytrid fungus Batrachochytrium dendrobatidis, is associated with recent declines in amphibian populations. Susceptibility to this disease varies among amphibian populations and species, and resistance appears to be attributable in part to the presence of antifungal microbial species associated with the skin of amphibians. The betaproteobacterium Janthinobacterium lividum has been isolated from the skins of several amphibian species and produces the antifungal metabolite violacein, which inhibits B. dendrobatidis. In this study, we added J. lividum to red-backed salamanders (Plethodon cinereus) to obtain an increased range of violacein concentrations on the skin. Adding J. lividum to the skin of the salamander increased the concentration of violacein on the skin, which was strongly associated with survival after experimental exposure to B. dendrobatidis. As expected from previous work, some individuals that did not receive J. lividum and were exposed to B. dendrobatidis survived. These individuals had concentrations of bacterially produced violacein on their skins that were predicted to kill B. dendrobatidis. Our study suggests that a threshold violacein concentration of about 18 μM on a salamander's skin prevents mortality and morbidity caused by B. dendrobatidis. In addition, we show that over one-half of individuals in nature support antifungal bacteria that produce violacein, which suggests that there is a mutualism between violacein-producing bacteria and P. cinereus and that adding J. lividum is effective for protecting individuals that lack violacein-producing skin bacteria.

Applied and Environmental Microbiology

85727432

10.4319/LO.2011.56.4.1310

Phase transitions of wax esters adjust buoyancy in diapausing Calanoides acutus

We study the composition and biophysical properties of wax esters extracted from the Antarctic copepod, Calanoides acutus, to explore if these factors adjust buoyancy in diapausing copepods. Levels of wax ester in the copepods were correlated with depth, with deeper animals containing higher amounts. An unsaturation index was used to determine the proportions of polyunsaturated wax esters in the oil sac of the copepods. The proportion of polyunsaturated wax ester in copepods that had descended to depth was always close to 50% and attributable to high amounts of the diatom biomarker fatty acid 20:5(n-3) contained in these storage lipids. High-pressure differential scanning calorimetry indicated that wax esters with such high levels of unsaturation exhibited unusual properties, changing from a liquid to a solid phase at pressures and temperatures below 500 m in the ocean. The dense, solid wax esters reduce the overall buoyancy of the lipid-rich copepods at depth and help facilitate neutral buoyancy. The composition of wax esters is a key factor in buoyancy control in these organisms during diapause. Many calanoid copepods inhabiting high-latitude environments overwinter at great depths in the oceans in a state of diapause, a condition where metabolic processes are either arrested or greatly reduced (Dahms 1995). A fundamental requirement of successful overwintering is the acquisition of substantial lipid reserves during summer when microplankton and particularly diatom production is

Limnology and Oceanography

86589096

10.1111/J.1365-2435.2011.01890.X

Preparing for hibernation in ground squirrels: adrenal androgen production in summer linked to environmental severity in winter

Summary 1. At high latitudes, evolutionary adaptations focus on those that maximize survival, with hibernation being a major one used by many smaller mammals. Typically, mammalian hibernators overwinter in sites that are ≈0°C. However, in arctic regions, such sites do not exist, necessitating hibernation at sites well below 0°C. Lipid, the normal fuel of most hibernators, may not provide sufficient glucose needed by certain tissues to permit survival, with muscle breakdown being required. Critical to enhancing muscle stores are high concentrations of anabolic androgens prior to hibernation when the gonads are inactive. 2. We compare and contrast androgen levels in arctic ground squirrels (AGS) (Urocitellus parryii Richardson) from the Yukon and Columbian ground squirrel (CGS) (U. columbianus Ord) from southern Alberta. 3. In males, changes in testes mass over the active season were similar between AGS and CGS. In contrast, during the breeding and the nonbreeding, pre-hibernation periods, androgen levels in AGS were 6–10 and 20–25 times, respectively, those of CGS. From the breeding to the pre-hibernation periods, androgen levels declined 41% in AGS, but 86% in CGS. In females, androgen levels in AGS were high throughout the active season and, prior to hibernation, were 24 times those in CGS. 4. In pre-hibernating AGS, we determined the source of these high androgen levels from two studies. First, using a hormonal challenge protocol to probe the hypothalamic-pituitary-adrenal axis, we found that androgen levels in both females and males decreased ≥10% in response to suppression by dexamethasone (an artificial glucocorticoid that inhibits ACTH release) and increased ≥18% in response to direct adrenal stimulation by adrenocorticorticotropic homone (ACTH). Second, by sequential hormonal injections in males of gonadotropin-releasing hormone (GnRH) and of ACTH coupled with gonadectomy (GDX), followed by adrenalectomy (ADX), we found that GnRH had no effect, whereas ACTH stimulated androgen levels by >40%, both before and after GDX. After ADX, levels fell by 80%. Thus, the adrenals, not the gonads, are the source of these androgens. 5. We hypothesize that pre-hibernating AGS have evolved a solution seen in no other known mammal: exploiting the benefits of high adrenal androgen levels prior to hibernation to build muscle that is then catabolized overwinter. The unknown is how AGS have mitigated the costs of these high androgen levels.

Functional Ecology

84088544

10.1111/J.1365-2745.2009.01601.X

The ecological engineering impact of a single tree species on the soil microbial community

1. Ecosystem engineering by a single species can have a cascading effect on many ecosystem processes. While the impact of above-ground ecological engineers on soil chemical properties has been studied, few studies have assessed their impact on the soil microbial community, which is largely responsible for many ecosystem functions. 2. Utilizing a long-term experiment where birch was planted on heather moorland 20 years ago, the engineering impact of a single tree species (Betula pubescens) on the soil microbial community was assessed using phospholipid fatty acid (PLFA) analysis and fungal polymerase chain reaction–denaturing gradient gel electrophoresis (PCR-DGGE). Changes in the soil microbial community were then related to soil chemical and physical variables and tree performance variables. 3. Under birch, total microbial biomass (total PLFA) declined, species richness increased and the ratio of fungal : bacterial PLFA declined. The fungal PLFA marker increased with increasing organic matter and depth of the LFH and O soil horizons, characteristics associated with moorland soils. Bacterial PLFAs increased with increasing birch canopy cover. The fungal community of the birch plots was different from that in the heather plots and changes in the fungal community composition were related to the size of the birch trees in the plots. 4. Changes in the soil microbial community were also related to changes in mineralizable N. Mineralizable N was correlated with both decreasing total soil microbial biomass and decreasing fungal : bacterial ratio. 5. The durability of the engineering effects of birch was studied in a second experiment. Plots were established in first-generation birch woodland that had developed on Calluna-dominated moorland. The plots were cleared of birch and planted with heather. After 20 years, there was no difference in the community composition of the PLFAs. In contrast, there were significant differences in the fungal community composition as judged by DGGE analysis, with the fungal community in the felled birch plots being similar to the heather moorland. 6. Synthesis. This work demonstrates that addition of a single tree species to heather moorland results in changes in below-ground soil microbial communities and in nutrient cycling.

Journal of Ecology

6317232

10.1186/1471-2148-10-214

Molecular basis of a novel adaptation to hypoxic-hypercapnia in a strictly fossorial mole

BackgroundElevated blood O2 affinity enhances survival at low O2 pressures, and is perhaps the best known and most broadly accepted evolutionary adjustment of terrestrial vertebrates to environmental hypoxia. This phenotype arises by increasing the intrinsic O2 affinity of the hemoglobin (Hb) molecule, by decreasing the intracellular concentration of allosteric effectors (e.g., 2,3-diphosphoglycerate; DPG), or by suppressing the sensitivity of Hb to these physiological cofactors.ResultsHere we report that strictly fossorial eastern moles (Scalopus aquaticus) have evolved a low O2 affinity, DPG-insensitive Hb - contrary to expectations for a mammalian species that is adapted to the chronic hypoxia and hypercapnia of subterranean burrow systems. Molecular modelling indicates that this functional shift is principally attributable to a single charge altering amino acid substitution in the β-type δ-globin chain (δ136Gly→Glu) of this species that perturbs electrostatic interactions between the dimer subunits via formation of an intra-chain salt-bridge with δ82Lys. However, this replacement also abolishes key binding sites for the red blood cell effectors Cl-, lactate and DPG (the latter of which is virtually absent from the red cells of this species) at δ82Lys, thereby markedly reducing competition for carbamate formation (CO2 binding) at the δ-chain N-termini.ConclusionsWe propose this Hb phenotype illustrates a novel mechanism for adaptively elevating the CO2 carrying capacity of eastern mole blood during burst tunnelling activities associated with subterranean habitation.

BMC Evolutionary Biology

11093057

10.1242/JEB.00979

Hypoxic survival strategies in two fishes: extreme anoxia tolerance in the North European crucian carp and natural hypoxic preconditioning in a coral-reef shark

SUMMARY Especially in aquatic habitats, hypoxia can be an important evolutionary driving force resulting in both convergent and divergent physiological strategies for hypoxic survival. Examining adaptations to anoxic/hypoxic survival in hypoxia-tolerant animals may offer fresh ideas for the treatment of hypoxia-related diseases. Here, we summarise our present knowledge of two fishes that have evolved to survive hypoxia under very different circumstances. The crucian carp (Carassius carassius) is of particular interest because of its extreme anoxia tolerance. During the long North European winter, it survives for months in completely oxygen-deprived freshwater habitats. The crucian carp also tolerates a few days of anoxia at room temperature and, unlike anoxia-tolerant freshwater turtles, it is still physically active in anoxia. Moreover, the crucian carp does not appear to reduce neuronal ion permeability during anoxia and may primarily rely on more subtle neuromodulatory mechanisms for anoxic metabolic depression. The epaulette shark (Hemiscyllium ocellatum) is a tropical marine vertebrate. It lives on shallow reef platforms that repeatedly become cut off from the ocean during periods of low tides. During nocturnal low tides, the water [O2] can fall by 80% due to respiration of the coral and associated organisms. Since the tides become lower and lower over a period of a few days, the hypoxic exposure during subsequent low tides will become progressively longer and more severe. Thus, this shark is under a natural hypoxic preconditioning regimen. Interestingly, hypoxic preconditioning lowers its metabolic rate and its critical PO2. Moreover, repeated anoxia appears to stimulate metabolic depression in an adenosine-dependent way.

The Journal of Experimental Biology

23938751

10.1007/BF00610241

Thermoperception in the common vampire bat (Desmodus rotundus)

Summary1.The common vampire bat,Desmodus rotundus, is known to be capable of detecting temperature differences. In the experiments described here two animals were trained to give preference to the radiation emitted by a warm signal unit (the negative unit was left at room temperature). The distance between the decision line and the signal units was 8, 12 or 16 cm. Both animals responded to radiation as low as 0.5 × 10−4 W cm−2 (Fig. 3).2.Based on calculations of the radiation emitted by the human skin, vampires should be capable of detecting warm-blooded animals at a distance up to 16 cm (Fig. 4). This sense for thermal radiation may aid these bats in localizing or selecting a suitable biting site.3.Histological studies of the bats' facial structures indicate that thermal stimuli are most probably perceived in the three pits surrounding the central nose leaf: the thin, hairless and glandless skin is underlaid with dense connective tissue. Thermography reveals that the surface temperature of the nasal region is up to 9 °C lower than that of the neighboring parts of the face (Fig. 2).

Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology

1279919

10.1007/BF00610867

The physiology of vocalization by the echolocating oilbird,Steatornis caripensis

Summary1.Oilbirds (Steatornis caripensis; Steatornithidae) have a bilaterally asymmetrical bronchial syrinx (Fig. 2) with which they produce echolocating clicks and a variety of social vocalizations. The sonar clicks typically have a duration of about 40 to 50 ms and can be classified as continuous, double or single. Agonistic squawks typically have a duration of about 0.5 s and contain multiple harmonic components (Figs. 5, 6).2.Both sonar clicks and agonistic squawks are initiated by contraction of the sternotrachealis muscles (Figs. 7 and 16) which stretch the trachea, reducing the tension across the syrinx and causing the cartilaginous bronchial semi-rings supporting the cranial and caudal edges of the external tympaniform membranes (ETM) to hinge inward, folding the ETM into the syringeal lumen (Fig. 17). Bernoulli forces created by expiratory air flowing through the restricted syringeal aperture presumably initiate vibration of the internal and/or external tympaniform membranes.3.Social vocalizations such as the agonistic squawk, continue until the sternotrachealis muscles relax (Fig. 10), allowing the cranial portion of the bronchus to move anteriad and abducting the ETM.4.Sonar clicks are terminated by rapid contraction of a previously undescribed intrinsic syringeal muscle, the broncholateralis, which inserts on the semi-ring supporting the anterior edge of the ETM and causes it to rotate about its articulation with the next anterior bronchial cartilage in such a way that it abducts the ETM (Figs. 8, 16, 17). Musculus broncholateralis contracts only during sonar clicks, appears to have a high proportion of twitch-type fibers, and is specialized for the rapid abduction of the ETM to produce short duration, click-like vocalizations.5.Tracheal airflow and sternal air sac pressure reflect the changes in the syringeal aperture. Tracheal airflow at first increases as expiratory effort increases subsyringeal pressure. The initial high rate of airflow drops at the onset of phonation due to the increased syringeal resistance. In the case of a double click, airflow momentarily ceases during the intraclick interval when the ETM temporarily closes the syrinx. Air sac pressure rises to its maximum level at this time. Expiratory airflow rapidly increases as the ETM is abducted from either its closed or phonatory position to its open, resting position. Each sonar click requires about 1 cm3 of air; a typical agonistic squawk may use about 27 cm3 of air (Figs. 11, 12, 13; Tables 3, 4).6.Each sonar click is often accompanied by a complete respiratory cycle or ‘mini-breath’ (Fig. 11). Pulmonary ventilation can be controlled independently from the clicking rate by varying the tidal volume of the mini-breaths, which may be as small as the tracheal and bronchial dead space. Mini-breaths permit oilbirds to produce click trains having a long train duration uninterrupted by a long inspiration.7.A dual flow probe was used to simultaneously measure the rate of airflow through each semi-syrinx during vocalization. The rate of airflow through the right semi-syrinx was 40 to 60% greater than that through the left. Both syringes functioned together except during the middle portion of some continuous type sonar clicks when sound was sometimes generated only by one semi-syrinx, the other being closed (Figs. 14, 15; Tables 5, 6).8.The fluid subsyringeal power reaches approximately 100 and 150 mW in the left and right semi-syrinx, respectively, during the second member of a double sonar click (Table 6). Total syringeal power during agonistic squawks reaches at least 60 mW and syringeal resistance during these vocalizations is as high as 1500 cm H20/LPS (Table 7).

Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology

28234765

10.1007/BF01049065

The evolution of sweat glands

Mammals have two kinds of sweat glands, apocrine and eccrine, which provide for thermal cooling. In this paper we describe the distribution and characteristics of these glands in selected mammals, especially primates, and reject the suggested development of the eccrine gland from the apocrine gland during the Tertiary geological period. The evidence strongly suggests that the two glands, depending on the presence or absence of fur, have equal and similar functions among mammals; apocrine glands are not primitive. However, there is a unique and remarkable thermal eccrine system in humans; we suggest that this system evolved in concert with bipedalism and a smooth hairless skin.

International Journal of Biometeorology

34966023

10.1007/S00226-005-0065-2

Biodegradation of new quaternary ammonium compounds in treated wood by mould fungi

The degradation of seven potential wood preservatives based on imidazolium compounds (ICs) and quaternary ammonium compounds (QACs) with a modified anion structure by mould fungi was determined using soil-block method. Experiments were carried out on Scots pine (Pinus sylvestris L.) wood. Two-phase titration and high-performance liquid chromatography (HPLC) method were used to detect and quantify the degradation products. The performed soil-block tests showed that the ICs and QACs with alkoxymethyl substituents were leached from the experimental wood when in contact with moist soil and revealed their fungal detoxification by mould fungi, especially by Gliocladium roseum. The degree of biological decomposition of new compounds was higher than didecyldimethylammonium chloride and didecylmethylpoli(oxyethyl)ammonium propionate. The observations of the colonization by mould fungi were made using the scanning electron microscope (SEM). Decay of treated wood by mould fungi showed its tolerance to QACs.

Wood Science and Technology

10292791

10.1007/S00442-012-2575-6

Aerial roots of epiphytic orchids: the velamen radicum and its role in water and nutrient uptake

The velamen radicum, a spongy, usually multiple epidermis of the roots, which at maturity consists of dead cells, is frequently described as an important adaptation of epiphytic orchids. Yet, quantitative evidence for the alleged functions, e.g., efficient water and nutrient uptake, nutrient retention, reduction of water loss, mechanical protection, or the avoidance of overheating, is rare or missing. We tested the notion originally put forward by Went in 1940 that the velamen allows plants to capture and immobilize the first solutions arriving in a rainfall, which are the most heavily charged with nutrients. In a series of experiments, we examined whether all necessary functional characteristics are given for this scenario to be realistic under ecological conditions. First, we show that the velamen of a large number of orchid species takes up solutions within seconds, while evaporation from the velamen takes several hours. Charged ions are retained in the velamen probably due to positive and negative charges in the cell walls, while uncharged compounds are lost to the external medium. Finally, we demonstrate that nutrient uptake follows biphasic kinetics with a highly efficient, active transport system at low external concentrations. Thus, our results lend strong support to Went’s hypothesis: the velamen fulfills an important function in nutrient uptake in the epiphytic habitat. Most of the other functions outlined above still await similar experimental scrutiny.

Oecologia

59129789

10.1007/S00227-001-0710-8

Average nanorough skin surface of the pilot whale (Globicephalamelas, Delphinidae): considerations on the self-cleaning abilities based on nanoroughness

Abstract. In aquatic environments, the biofouling process is assumed to initiate from the conditioning layer of absorbed organic carbon residues on wetted surfaces. Microfouling organisms attach to this conditioning layer, building up a biofilm on which further biofouling proceeds. In dolphins, biofouling reduces hydrodynamic efficiency and may negatively affect health if not managed. In the present study we examined the skin surface of the pilot whale (Globicephalamelas). Employing cryo-scanning electron microscopic techniques combined with various sample preparations, the skin displayed an average nanorough surface characterized by a pattern of nanoridge-enclosed pores; the average pore size (approximately 0.20 µm2) was below the size of most marine biofouling organisms. Further, the implications of this type of surface to the self-cleaning abilities of the skin of pilot whales are discussed, based on reduced available space for biofouler attachment, the lack of any particular microniches as shelters for biofoulers, and the challenges of turbulent water flow and liquid–air interfaces during surfacing and jumping of the dolphin.

Marine Biology

73796

10.1007/S004420050198

Alternative fire resistance strategies in savanna trees

Abstract Bark properties (mainly thickness) are usually presented as the main explanation for tree survival in intense fires. Savanna fires are mild, frequent, and supposed to affect tree recruitment rather than adult survival: trunk profile and growth rate of young trees between two successive fires can also affect survival. These factors and fire severity were measured on a sample of 20 trees near the recruitment stage of two savanna species chosen for their contrasted fire resistance strategies (Crossopteryx febrifuga and Piliostigma thonningii). Crossopteryx has a higher intrinsic resistance to fire (bark properties) than Piliostigma: a 20-mm-diameter stem of Crossopteryx survives exposure to 650°C, while Piliostigma needs a diameter of at least 40 mm to survive. Crossopteryx has a thicker trunk than Piliostigma: for two trees of the same height, the basal diameter of Crossopteryx will be 1.6 times greater. Piliostigma grows 2.26 times faster than Crossopteryx between two successive fires. The two species have different fire resistance strategies: one relies on resistance of aboveground structures to fire, while the other relies on its ability to quickly re-build aboveground structures. Crossopteryx is able to recruit in almost any fire conditions while Piliostigma needs locally or temporarily milder fire conditions. In savannas, fire resistance is a complex property which cannot be assessed simply by measuring only one of its components, such as bark thickness. Bark properties, trunk profile and growth rate define strategies of fire resistance. Fire resistance may interact with competition: we suggest that differences in fire resistance strategies have important effects on the structure and dynamics of savanna ecosystems.

Oecologia

9380561

10.1007/S12600-010-0087-7

The activity of a selected extract of Drimys winteri bark and polygodial on settling and probing behavior of the lettuce aphid Nasonovia ribisnigri

An n-hexane extract and the sesquiterpene polygodial isolated from the bark of Drimys winteri J.R. Forster & G. Forster (Winteraceae) were tested to assess their ability to inhibit settling of the aphid Nasonovia ribisnigri Mosley on lettuce leaves; assessments were made using a choice and no-choice leaf-disk assay. The n-hexane extract and the polygodial both significantly inhibited settling in the choice and no-choice tests, but their application on lettuce leaves did not result in any aphid mortality. Probing behavior of N. ribisnigri on polygodial-treated plants was assessed by means of the electrical penetration graph technique. Polygodial interfered with aphid probing behavior by reducing the total probing time, the number of probes, and the number of intracellular punctures. Aphids did not reach the sieve elements of polygodial-treated plants during the 2-h access period. Both tested compounds have the potential to be used in the development of lettuce aphid control agents to reduce the risk of virus transmission.

Phytoparasitica

136873114

10.1016/S1672-6529(10)60252-1

Bionic photovoltaic panels bio-inspired by green leaves

In strong solar light, silicon solar panels can heat up by 70°C and, thereby, loose approximately one third of their efficiency for electricity generation. Leaf structures of plants on the other hand, have developed a series of technological adaptations, which allow them to limit their temperature to 40–45°C in full sunlight, even if water evaporation is suppressed. This is accomplished by several strategies such as limitation of leaf size, optimization of aerodynamics in wind, limitation of absorbed solar energy only to the useful fraction of radiation and by efficient thermal emission. Optical and infrared thermographic measurements under a solar simulator and in a streaming channel were used to investigate the corresponding properties of leaves and to identify suitable bionic model systems. Experiments started with the serrated structure of ordinary green leaves distributed over typical twig structures and finally identified the Australian palm tree Licuala ramsayi as a more useful bionic model. It combines a large area for solar energy harvesting with optimized aerodynamic properties for cooling and is able to restructure itself as a protection against strong winds. The bionic models, which were constructed and built, are analyzed and discussed.

Journal of Bionic Engineering

86195166

10.1046/J.0028-646X.2001.00299.X

Epicormic strand structure in Angophora, Eucalyptus and Lophostemon (Myrtaceae): implications for fire resistance and recovery

Summary • Epicormic bud producing structures in the eucalypts, a large group of woody plants of considerable ecological, horticultural and silvicultural importance, are described here. • The outer portion of epicormic strands excised from the bark of large diameter stems of 18 Eucalyptus species, two Angophora species and Lophostemon confertus was examined anatomically in semithin sections. • In the inner bark each eucalypt strand usually possessed 5–12 radially orientated strips of tissue of meristematic appearance. The meristem strips were c. 30–50 µm high, 70–110 µm wide and 2000–10 000 µm long, with a lacuna above the meristem surface. Few buds or bud primordia were associated with the strands and the strands appeared to have a reduced regenerative potential in the outer bark. • In most angiosperm trees dormant epicormic buds are present in the outer bark, a position where they could be killed by fire. By contrast, in eucalypts the greatest epicormic bud initiation potential is at the level of the vascular cambium, which is protected by the maximum bark thickness. This might explain the pronounced ability of eucalypts to produce bole and branch epicormic shoots after moderate to intense fire.

New Phytologist

46923063

10.1002/(SICI)1097-4687(199710)234:1<1::AID-JMOR1>3.0.CO;2-I

Ultrastructural architecture of the microtrichia of the insect cuticle

The ultrastructure of the microtrichia (MT) of the insect cuticle was studied using scanning electron microscopy (SEM). After dissolving the protein matrix of chitin‐protein microfibrils with NaOH, the orientation of the axial chitin fibers was three‐dimensionally demonstrated. Microfibrils of the outermost exocuticular lamella lie parallel to the slope of the cone surface of the MT and rotate slightly on the top of the MT. Microfibrils of the external lamella of the transitional area between planar cuticle and conical cuticle of the MT corresponded to the shape of the surface within one lamella and preferred directions of MT's microfibrils in the successive lamella rotated. In the deeper layers of the cuticle, the rotation of both the microfibrils and successive lamella results in the twisted straw architecture of the microfibrils' composition within the MT. The deepest microfibrils that are located close to the axis of the MT form compact clusters of fibrils (1.0–1.5 μm length). The twisted‐straw architecture of microfibrils in the MT is derived from principles of development of extracellular fibrous composites. It is suggested, however, that this architecture has an additional functional significance as a strategic design with particular mechanical properties. J. Morphol. 234:1–10, 1997. © 1997 Wiley‐Liss, Inc.

Journal of Morphology

137373088

10.1002/ADEM.201080065

Pummelos as Concept Generators for Biomimetically Inspired Low Weight Structures with Excellent Damping Properties

Natural materials often exhibit excellent mechanical properties. An example of outstanding impact resistance is the pummelo fruit (Citrus maxima) which can drop from heights of 10 m and more without showing significant outer damage. Our data suggest that this impact resistance is due to the hierarchical organization of the fruit peel, called pericarp. The project presented in the current paper aims at transferring structural features from the pummelo pericarp to engineering materials, in our case metal foams, produced by the investment casting process. The transfer necessitates a detailed structural and mechanical analysis of the biological model on the one hand, and the identification and development of adequate materials and processes on the other hand. Based on this analysis, engineering composite foam structures are developed and processed which show enhanced damping and impact properties. The modified investment casting process and the model alloy Bi57Sn43 proved to be excellent candidates to make these bio-inspired structures. Mechanical testing of both the natural and the engineering structures has to consider the necessity to evaluate the impact of the different hierarchical features. Therefore, specimens of largely varying sizes have to be tested and size effects cannot be ignored, especially as the engineering structures might be upscaled in comparison with the natural role model. All in all, the present results are very promising: the basis for a transfer of bio-inspired structural hierarchical levels has been set.

Advanced Engineering Materials

36699934

10.1111/J.1365-2915.2005.00577.X

Antibacterial properties of larval secretions of the blowfly, Lucilia sericata

Abstract.  The antibacterial properties of secretions aseptically collected from larvae of the greenbottle fly Lucilia sericata (Meigen) (Diptera: Calliphoridae) were examined. These investigations revealed the presence of small (<1 kDa) antibacterial factor(s) within the larval secretions, active against a range of bacteria. These include the Gram‐positive Staphylococcus aureus, both methicillin‐resistant Staphylococcus aureus (MRSA) and methicillin‐sensitive Staphylococcus aureus (MSSA), Streptococcus pyogenes and to a lesser extent the Gram‐negative Pseudomonas aeruginosa. These secretions were shown to be highly stable as a freeze‐dried preparation and, considering the activity against organisms typically associated with clinical infection, may be a source of novel antibiotic‐like compounds that may be used for infection control and in the fight against MRSA.

Medical and Veterinary Entomology

1457374

10.1111/J.1461-0248.2010.01501.X

Predator-released hydrocarbons repel oviposition by a mosquito.

Prey species commonly use predator-released kairomones (PRKs) to detect risk of predation, yet the chemical identity of PRKs remains elusive. Chemical identification of PRKs will facilitate the study of predator-prey interactions and the risk of predation, and when the prey are pests, will potentially provide environmentally friendly means of pest control. In temporary pools of the Mediterranean and Middle East, larvae of the mosquito Culiseta longiareolata Macquart are highly vulnerable to the common predatory backswimmer, Notonecta maculata Fabricius. We demonstrate that N. maculata releases two hydrocarbons, n-heneicosane and n-tricosane, which repel ovipositing females of C. longiareolata. In behavioural tests with environmentally relevant chemical concentrations in outdoor mesocosm experiments, the repellent effects of the two compounds were additive at the tested concentrations.

Ecology Letters

85065678

10.1111/J.1748-7692.1998.TB00716.X

PREHENSILE USE OF PERIORAL BRISTLES DURING FEEDING AND ASSOCIATED BEHAVIORS OF THE FLORIDA MANATEE (TRICHECHUS MANATUS LATIROSTRIS)

The use of perioral bristles (modified vibrissae) by 17 captive Florida manatees and approximately 20 wild manatees was analyzed. Captive manatees were fed six species of aquatic vegetation normally eaten in the wild (four freshwater species and two seagrasses). Inanimate objects were placed in the holding tanks with manatees at Lowry Park Zoological Gardens (Tampa, FL) to determine the degree to which perioral bristles were used in exploration and to define the range of manipulative behavior. In addition, behavioral observations were made on the use of perioral bristles during social interactions with conspecifics. Observations were recorded using a Hi8-format video camera. Florida manatees possess an unusually large degree of fine motor control of the snout and perioral bristles. The large and robust perioral bristle fields of the upper lip were used in a prehensile manner during feeding. Bristle use by manatees feeding on submerged vegetation differed from that seen during feeding on floating vegetation. Other behavioral use of the perioral bristles shows variation depending upon the situation encountered. The degree of plasticity of perioral bristle use supports our hypothesis that the vibrissal-muscular complex of the Florida manatee has evolved to increase the efficiency of grazing and browsing on aquatic vegetation and to fully maximize the potential of the manatee as a generalist feeder. The manipulative and sensitive nature of the manatee snout is likely a manifestation of a complex sensory and motor system which has evolved for marine mammal aquatic herbivores living in shallow turbid habitats.

Marine Mammal Science

84758246

10.1111/J.1748-7692.1998.TB00717.X

THE MUSCULAR HYDROSTAT OF THE FLORIDA MANATEE (TRICHECHUS MANATUS LATIROSTRIS): A FUNCTIONAL MORPHOLOGICAL MODEL OF PERIORAL BRISTLE USE

Facial musculature was examined in the Florida manatee, Tricbecbus manatus latirostris, in order to develop a functional model of perioral bristle use. Muscles identified include the M. levator nasolabialis, M. buccinatorius, M. maxillonasolabialis, M. centralis nasi, M. lateralis nasi, M. spbincter colli profundus pars oris, M. orbicularis oris, M. mandibularis, and M. mentalis. A new muscle, M. centralis nasi, has been named and is an integral part of perioral bristle movement. The snout of the Florida manatee is capable of performing complex movements. The prehensile ability of Florida manatees can be explained in the context of a muscular hydrostat as defined by Kier and Smith (1985). Eversion of certain bristles in the upper lip occurs by shortening longitudinal, transverse, and semicircular muscles in combination with volume displacement due to compensatory changes in the shape of the snout. Midline sweeping of these bristles is accomplished by the contraction of M. centralis nasi. Eversion of bristles on the lower jaw is a result of shortening of M. mentalis. Contraction of M. orbicularis oris pushes vegetation into the oral cavity. All observed movement patterns and uses of perioral bristles can be explained by variation of these sequences within the context of muscular hydrostat function.

Marine Mammal Science

20114403

10.1002/YEA.1148

Mycosporine‐glutaminol‐glucoside, a UV‐absorbing compound of two Rhodotorula yeast species

High‐performance liquid chromatography (HPLC), alone or in combination with mass spectrometry (MS), was used to screen the basidiomycetous yeasts Rhodotorula minuta and R. slooffiae isolated from lakes for the presence of UV‐absorbing compounds. Mycosporine‐glutaminol‐glucoside (maximum absorption, 310 nm), a UV‐photoprotective mycosporine known in terrestrial fungi, was the major UV‐absorbing compound found in these species. This is the first identification of a mycosporine in yeasts. The presence of this compound seems to be a promising chemotaxonomical marker for yeast systematics. Copyright © 2004 John Wiley & Sons, Ltd.

Yeast

32340025

10.1042/BJ3560503

Novel barnacle underwater adhesive protein is a charged amino acid-rich protein constituted by a Cys-rich repetitive sequence.

Barnacle cement is an underwater adhesive that is used for permanent settlement, and is an insoluble protein complex. A method for rendering soluble the cement of Megabalanus rosa has been developed, and three major proteins have been identified in a previous study. To survey the M. rosa cement proteins in a lower molecular mass range, the cement proteins were separated by reversed-phase HPLC and a previously unidentified protein named 20 kDa M. rosa cement protein (Mrcp-20k) was found. Mrcp-20k cDNA was cloned to reveal its primary structure. This cDNA was 902 bp long and encoded a 202 amino acid-long open reading frame, including 19 amino acids of the signal sequence. The molecular mass in the disulphide form was calculated to be 20357 Da and the isoelectric point of the mature polypeptide was 4.72. Mrcp-20k was characterized by an abundance of Cys residues and charged amino acids. The most common amino acid was Cys (17.5%), with Asp (11.5%), Glu (10.4%) and His (10.4%) following in order of magnitude. The alignment of the Cys residues indicated the primary structure of this protein to consist of six degenerated repeats, each about 30 residues long. Mrcp-20k has no intermolecular disulphide bonds and no free thiol groups of Cys in the insoluble cement complex. Abundant Cys is thought to play a role in maintaining the topology of charged amino acids on the molecular surface by intramolecular disulphide-bond formation. The possible function of abundant charged amino acids, including the interaction with a variety of surface metals on the substratum, is discussed.

8315410

10.1007/S00248-006-9109-X

Eisenia fetida (Oligochaeta, Lumbricidae) Activates Fungal Growth, Triggering Cellulose Decomposition During Vermicomposting

Cellulose is the most abundant polymer in nature and constitutes a large pool of carbon for microorganisms, the main agents responsible for soil organic matter decomposition. Cellulolysis occurs as the result of the combined action of fungi and bacteria with different requirements. Earthworms influence decomposition indirectly by affecting microbial population structure and dynamics and also directly because the guts of some species possess cellulolytic activity. Here we assess whether the earthworm Eisenia fetida (Savigny 1826) digests cellulose directly (i.e., with its associated gut microbiota) and also whether the effects of E. fetida on microbial biomass and activity lead to a change in the equilibrium between fungi and bacteria. By enhancing fungal communities, E. fetida would presumably trigger more efficient cellulose decomposition. To evaluate the role of E. fetida in cellulose decomposition, we carried out an experiment in which pig slurry, a microbial-rich substrate, was treated in small-scale vermireactors with and without earthworms. The presence of earthworms in vermireactors significantly increased the rate of cellulose decomposition (0.43 and 0.26% cellulose loss day−1, with and without earthworms, respectively). However, the direct contribution of E. fetida to degradation of cellulose was not significant, although its presence increased microbial biomass (Cmic) and enzyme activity (cellulase and β-glucosidase). Surprisingly, as fungi may be part of the diet of earthworms, the activity of E. fetida triggered fungal growth during vermicomposting. We suggest that this activation is a key step leading to more intense and efficient cellulolysis during vermicomposting of organic wastes.

Microbial Ecology

53871670

10.1007/S00442-018-4306-0

The avian “hibernation” enigma: thermoregulatory patterns and roost choice of the common poorwill

Compared to mammals, there are relatively few studies examining heterothermy in birds. In 13 bird families known to contain heterothermic species, the common poorwill (Phalaenoptilus nuttallii) is the only species that ostensibly hibernates. We used temperature-sensitive radio-transmitters to collect roost and skin temperature (Tskin) data, and winter roost preferences for free-ranging poorwills in southern Arizona. Further, to determine the effect of passive rewarming on torpor bout duration and active rewarming (i.e., the use of metabolic heat to increase Tskin), we experimentally shaded seven birds during winter to prevent them from passively rewarming via solar radiation. Poorwills selected winter roosts that were open to the south or southwest, facilitating passive solar warming in the late afternoon. Shaded birds actively rewarmed following at least 3 days of continuous torpor. Average torpor bout duration by shaded birds was 122 h and ranged from 91 to 164 h. Active rewarming by shaded birds occurred on significantly warmer days than those when poorwills remained torpid. One shaded bird remained inactive for 45 days, during which it spontaneously rewarmed actively on eight occasions. Our findings show that during winter poorwills exhibit physiological patterns and active rewarming similar to hibernating mammals.

Oecologia

20382668

10.1021/JA104996Y

Oysters produce an organic-inorganic adhesive for intertidal reef construction.

Coastal ecosystems rely upon oyster reefs to filter water, provide protection from storms, and build habitat for other species. From a chemistry perspective, few details are available to illustrate how these shellfish construct such extensive reef systems. Experiments presented here show that oysters generate a biomineralized adhesive material for aggregating into large communities. This cement is an organic-inorganic hybrid and differs from the surrounding shells by displaying an alternate CaCO(3) crystal form, a cross-linked organic matrix, and an elevated protein content. Emerging themes and unique aspects are both revealed when comparing oyster cement to the adhesives of other marine organisms. The presence of cross-linked proteins provides an analogy to mussel and barnacle adhesives whereas the high inorganic content is exclusive to oysters. With a description of oyster cement in hand we gain strategies for developing synthetic composite materials as well as a better understanding of the components needed for healthy coastal environments.

Journal of the American Chemical Society