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14765494

10.1242/JEB.01312

Cold-stable eye lens crystallins of the Antarctic nototheniid toothfish Dissostichus mawsoni Norman

SUMMARY The eye lenses of the Antarctic nototheniid fishes that inhabit the perennially freezing Antarctic seawater are transparent at –2°C, whereas the cold-sensitive mammalian and tropical fish lenses display cold-induced cataract at 20°C and 7°C, respectively. No cold-cataract occurs in the giant Antarctic toothfish Dissostichus mawsoni lens when cooled to temperatures as low as –12°C, indicating highly cold-stable lens proteins. To investigate this cold stability, we characterised the lens crystallin proteins of the Antarctic toothfish, in parallel with those of the sub-tropical bigeye tuna Thunnus obesus and the endothermic cow Bos taurus, representing three disparate thermal climes (–2°C, 18°C and 37°C, respectively). Sizing chromatography resolved their lens crystallins into three groups,α /βH, β and γ, with γ crystallins being the most abundant (>40%) lens proteins in fish, in contrast to the cow lens where they comprise only 19%. The upper thermal stability of these crystallin components correlated with the body temperature of the species. In vitro chaperone assays showed that fish α crystallin can protect same-species γ crystallins from heat denaturation, as well as lysozyme from DTT-induced unfolding, and therefore are small Heat Shock Proteins (sHSP) like their mammalian counterparts. Dynamic light scattering measured an increase in size of αγ crystallin mixtures upon heating, which supports formation of the αγ complex as an integral part of the chaperone process. Surprisingly, in cross-species chaperone assays, tunaα crystallins only partly protected toothfish γ crystallins, while cow α crystallins completely failed to protect, indicating partial and no αγ interaction, respectively. Toothfish γ was likely to be the component that failed to interact, as the supernatant from a cowα plus toothfish γ incubation could chaperone cow γ crystallins in a subsequent heat incubation, indicating the presence of uncomplexed cow α. This suggests that the inability of toothfish γ crystallins to fully complex with tuna α, and not at all with the cowα crystallins, may have its basis in adaptive changes in the protein that relate to the extreme cold-stability of the toothfish lens.

The Journal of Experimental Biology

18680315

10.1016/J.CUB.2008.11.061

A Novel Vertebrate Eye Using Both Refractive and Reflective Optics

Sunlight is attenuated rapidly in the ocean, resulting in little visually useful light reaching deeper than approximately 1000 m in even the clearest water. To maximize sensitivity to the relatively brighter downwelling sunlight, to view the silhouette of animals above them, and to increase the binocular overlap of their eyes, many mesopelagic animals have developed upward-pointing tubular eyes. However, these sacrifice the ability to detect bioluminescent and reflective objects in other directions. Thus, some mesopelagic fish with tubular eyes extend their visual fields laterally and/or ventrally by lensless ocular diverticula, which are thought to provide unfocused images, allowing only simple detection of objects, with little spatial resolution. Here, we show that a medial mirror within the ventrally facing ocular diverticulum of the spookfish, Dolichopteryx longipes, consisting of a multilayer stack derived from a retinal tapetum, is used to reflect light onto a lateral retina. The reflective plates are not orientated parallel to the surface of the mirror. Instead, plate angles change progressively around the mirror, and computer modeling indicates that this provides a well-focused image. This is the first report of an ocular image being formed in a vertebrate eye by a mirror.

Current Biology

161261491

10.1126/SCIENCE.291.5510.1884

Patience Yields Secrets of Seed Longevity

BOTANYHow long can a seed survive in the dark, cold ground, yet still burst into life when blessed by sun or rain? A pioneering experiment begun over a century ago to answer this question has become the world's longest running seed viability experiment. Along the way, it has inspired scientists in a growing number of fields worldwide to explore the mystery of seed longevity.

Science

81064998

10.1007/978-1-4419-7162-3_19

Arsenic Hyperaccumulator Fern Pteris vittata: Utilities for Arsenic Phytoremediation and Plant Biotechnology

Arsenic is a toxic metalloid that is widespread in the environment due to both man-made and natural causes. Soils, food, and ground water contaminated with arsenic pose serious health risks to millions of people in different parts of the World. While engineering methods to remediate arsenic-contaminated environments are available, they are often prohibitively expensive and cumbersome. It was discovered about a decade ago that the Chinese brake fern (Pteris vittata) had an extraordinary ability to tolerate and hyperaccumulate arsenic, up to about 2% of dry weight in its fronds. This opened up new opportunities to develop the brake fern for a cost-effective green technology to remediate arsenic-contaminated environments. The objective of this review is to highlight some of the salient findings on this and related ferns regarding their arsenic tolerance and hyperaccumulation traits. Investigations have shown that arsenic hyperaccumulation in brake fern has evolved as a defense against herbivory. Research employing molecular biology tools have identified some of the key genes and proteins important for arsenic metabolism in this species including genes for arsenic-induced oxidative stress. Comparative biochemistry of how organisms adapt to arsenic suggests that many other fern genes related to arsenic transport and metabolism are yet to be characterized in this fern. Our research indicates that brake fern could be a source of genes that could inform us about how plants adapt to abiotic stress factors such as high temperature stress and drought that have oxidative stress as a component. Some of these genes can be expected to be valuable for improving crops for increased tolerance to stress.

Reviews in Environmental Science and Bio\/technology

13862880

10.1086/648065

An Intertidal Sea Star Adjusts Thermal Inertia to Avoid Extreme Body Temperatures

The body temperature of ectotherms is influenced by the interaction of abiotic conditions, morphology, and behavior. Although organisms living in different thermal habitats may exhibit morphological plasticity or move from unfavorable locations, there are few examples of animals adjusting their thermal properties in response to short‐term changes in local conditions. Here, we show that the intertidal sea star Pisaster ochraceus modulates its thermal inertia in response to prior thermal exposure. After exposure to high body temperature at low tide, sea stars increase the amount of colder‐than‐air fluid in their coelomic cavity when submerged during high tide, resulting in a lower body temperature during the subsequent low tide. Moreover, this buffering capacity is more effective when seawater is cold during the previous high tide. This ability to modify the volume of coelomic fluid provides sea stars with a novel thermoregulatory “backup” when faced with prolonged exposure to elevated aerial temperatures.

The American Naturalist

137028112

10.1016/S1672-6529(11)60014-0

Investigation of microstructure, natural frequencies and vibration modes of dragonfly wing

In the present work, a thorough investigation on the microstructural and morphological aspects of dragonfly wings was carried out using scanning electron microscope. Then, based on this study and the previous reports, a precise three-dimensional numerical model was developed and natural frequencies and vibration modes of dragonfly forewing were determined by finite element method. The results shown that dragonfly wings are made of a series of adaptive materials, which form a very complex composite structure. This bio-composite fabrication has some unique features and potential benefits. Furthermore, the numerical results show that the first natural frequency of dragonfly wings is about 168 Hz and bending is the predominant deformation mode in this stage. The accuracy of the present analysis is verified by comparison of calculated results with experimental data. This paper may be helpful for micro aerial vehicle design concerning dynamic response.

Journal of Bionic Engineering

18931425

10.1146/ANNUREV.FLUID.36.050802.121940

DISSECTING INSECT FLIGHT

▪ Abstract “What force does an insect wing generate?” Finding answers to this enduring question is an essential step toward our understanding of interactions of moving objects with fluids that enable most living species such as insects, birds, and fish to travel efficiently and us to follow similar suit with sails, oars, and airfoils. We give a brief history of research in insect flight and discuss recent findings in unsteady aerodynamics of flapping flight at intermediate range Reynolds numbers (10–104). In particular, we examine the unsteady mechanisms in uniform and accelerated motions, forward and hovering flight, as well as passive flight of free-falling objects. The results obtained by “taking the insects apart” helped us to resolve previous puzzles about the force estimates in hovering insects, to ellucidate basic mechanisms essential to flapping flight, and to gain insights about the efficieny of flight.

Annual Review of Fluid Mechanics

5025765

10.5091/PLECEVO.2016.1174

A three-dimensional study of sub-foliar condensation in desert rhubarb (Rheum palaestinum, Polygonaceae)

The rare perennial plant species Rheum palaestinum Feinbr. (Polygonaceae), commonly known as desert rhubarb, is endemic to Jordan and southern Israel and grows in areas with low annual rainfall (Al-Eisawi 1998). It has an underground woody stem and grows mostly in shallow ravines of stonysandy terrains during the winter and early spring in years with above-normal precipitation. It produces one to four rounded leaves, 20–60 cm in diameter, with a wrinkled surface (fig. 1). The large leaf size of this species is atypical within arid ecosystems; in the presence of abundant sun, small leaf size is considered as one of the most common patterns of desert plants to decrease transpiration rates and increase water-use efficiency (Gibson 1996). The annual precipitation in Jordan’s desert is less than 75 mm, and January is the wettest month (Tarawneh & Kadıoğlu 2002). A preliminary study of the relationship between precipitation patterns and leaf growth suggested complex and under-studied water-absorption strategies for plants growing in arid environments. Our personal observations showed some unique morphologies and timing patterns that perennial plants in the tableland desert of Jordan have developed as survival strategies. A previous study showed that the large size and surface morphology of rhubarb leaves help to create a self-irrigation system and increase rainwater harvesting by 16-fold compared to other desert plants (Lev-Yadun et al. 2008). A simple leaf morphology can effectively drain rainwater without the need for wrinkles that dramatically increase leaf transpiration area, as has been shown for the lotus leaf (Barthlott & Neinhuis 1996). The leaf morphology of rhubarb may not play a crucial role in water collection, as rainfall is limited during its maximum growth period (March–April). Additionally, the leaves are tightly attached to the ground and the margins are bent downward to contact the soil; these morphological features favour the function of a vapour-trapping system under the leaf rather than water drainage on the upper surface. Rainwater collection is related to the leaf horizontal catchment area and not to the surface area maximized by the wrinkles. Because the water absorption rate needs to be higher than the transpiration rate, rhubarb leaf wrinkles increase the leaf surface area relative to the leaf footprint and

Plant Ecology and Evolution

32412719

10.1073/PNAS.90.11.5076

Three-dimensional structures of avidin and the avidin-biotin complex.

The crystal structures of a deglycosylated form of the egg-white glycoprotein avidin and of its complex with biotin have been determined to 2.6 and 3.0 A, respectively. The structures reveal the amino acid residues critical for stabilization of the tetrameric assembly and for the exceptionally tight binding of biotin. Each monomer is an eight-stranded antiparallel beta-barrel, remarkably similar to that of the genetically distinct bacterial analog streptavidin. As in streptavidin, binding of biotin involves a highly stabilized network of polar and hydrophobic interactions. There are, however, some differences. The presence of additional hydrophobic and hydrophilic groups in the binding site of avidin (which are missing in streptavidin) may account for its higher affinity constant. Two amino acid substitutions are proposed to be responsible for its susceptibility to denaturation relative to streptavidin. Unexpectedly, a residual N-acetylglucosamine moiety was detected in the deglycosylated avidin monomer by difference Fourier synthesis.

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

10305261

10.1242/JEB.034801

Elastic energy storage in the mantis shrimp's fast predatory strike

SUMMARY Storage of elastic energy is key to increasing the power output of many biological systems. Mantis shrimp (Stomatopoda) must store considerable elastic energy prior to their rapid raptorial strikes; however, little is known about the dynamics and location of elastic energy storage structures in this system. We used computed tomography (CT) to visualize the mineralization patterns in Gonodactylaceus falcatus and high speed videography of Odontodactylus scyllarus to observe the dynamics of spring loading. Using a materials testing apparatus, we measured the force and work required to contract the elastic structures in G. falcatus. There was a positive linear correlation between contraction force and contraction distance; alternative model tests further supported the use of a linear model. Therefore, we modeled the system as a Hookean spring. The force required to fully compress the spring was positively correlated with body mass and appendage size, but the spring constant did not scale with body size, suggesting a possible role of muscle constraints in the scaling of this system. One hypothesized elastic storage structure, the saddle, only contributed approximately 11% of the total measured force, thus suggesting that primary site of elastic energy storage is in the mineralized ventral bars found in the merus segment of the raptorial appendages. Furthermore, the intact system exhibited 81% resilience and severing the saddle resulted in a non-significant reduction to 77% resilience. The remarkable shapes and mineralization patterns that characterize the mantis shrimp's raptorial appendage further reveal a highly integrated mechanical power amplification system based on exoskeletal elastic energy storage.

The Journal of Experimental Biology

41169071

10.1098/RSPB.2006.3675

An experimental test of the contributions and condition dependence of microstructure and carotenoids in yellow plumage coloration

A combination of structural and pigmentary components is responsible for many of the colour displays of animals. Despite the ubiquity of this type of coloration, neither the relative contribution of structures and pigments to variation in such colour displays nor the relative effects of extrinsic factors on the structural and pigment-based components of such colour has been determined. Understanding the sources of colour variation is important because structures and pigments may convey different information to conspecifics. In an experiment on captive American goldfinches Carduelis tristis, we manipulated two parameters, carotenoid availability and food availability, known to affect the expression of carotenoid pigments in a full-factorial design. Yellow feathers from these birds were then analysed in two ways. First, we used full-spectrum spectrometry and high-performance liquid chromatography to examine the extent to which variation in white structural colour and total carotenoid content was associated with variation in colour properties of feathers. The carotenoid content of yellow feathers predicted two colour parameters (principal component 1—representing high values of ultraviolet and yellow chroma and low values of violet–blue chroma—and hue). Two different colour parameters (violet–blue and yellow chroma) from white de-pigmented feathers, as well as carotenoid content, predicted reflectance measurements from yellow feathers. Second, we determined the relative effects of our experimental manipulations on white structural colour and yellow colour. Carotenoid availability directly affected yellow colour, while food availability affected it only in combination with carotenoid availability. None of our manipulations had significant effects on the expression of white structural colour. Our results suggest that the contribution of microstructures to variation in the expression of yellow coloration is less than the contribution of carotenoid content, and that carotenoid deposition is more dependent on extrinsic variability than is the production of white structural colour.

Proceedings of The Royal Society B: Biological Sciences

90785148

10.5091/PLECEVO.2017.1284

Self-irrigation in the desert rhubarb Rheum palaestinum – a response to Khammash

Plant Ecology and Evolution

33222709

10.1111/J.1365-2672.2009.04554.X

Production of cell–cell signalling molecules by bacteria isolated from human chronic wounds

Aim:  To (i) identify chronic wound bacteria and to test their ability to produce acyl‐homoserine‐lactones (AHLs) and autoinducer‐2 (AI‐2) cell–cell signalling molecules and (ii) determine whether chronic wound debridement samples might contain these molecules.

Journal of Applied Microbiology

96591279

10.1016/S1672-6529(07)60001-8

Numerical simulation of electroosmotic flow near earthworm surface

The electroosmotic flow near an earthworm surface is simulated numerically to further understand the anti soil adhesion mechanism of earthworm. A lattice Poisson method is employed to solve electric potential and charge distributions in the electric double layer along the earthworm surface. The external electric field is obtained by solving a Laplace equation. The electroosmotic flow controlled by the Navier-Stokes equations with external body force is simulated by the lattice Boltzmann method. A benchmark test shows that accurate electric potential distributions can be obtained by the LPM. The simulation shows that the moving vortices, which probably contribute to anti soil adhesion, are formed near earthworm body surface by the nonuniform and variational electrical force.

Journal of Bionic Engineering

27675285

10.1007/S11829-007-9002-7

Mutations perturbing petal cell shape and anthocyanin synthesis influence bumblebee perception of Antirrhinum majus flower colour

We wished to understand the effects on pollinator behaviour of single mutations in plant genes controlling flower appearance. To this end, we analysed snapdragon flowers (Antirrhinum majus), including the mixta and nivea mutants, in controlled laboratory conditions using psychophysical tests with bumblebees. The MIXTA locus controls petal epidermal cell shape, and thus the path that incident light takes within the pigment-containing cells. The effect is that mixta mutant flowers are pink in comparison to the wild type purple flowers, and mutants lack the sparkling sheen of wild type flowers that is clearly visible to human observers. Despite their fundamentally different appearance to humans, and even though bees could discriminate the flowers, inexperienced bees exhibited no preference for either type, and the flowers did not differ in their detectability in a Y-maze—either when the flowers appeared in front of a homogeneous or a dappled background. Equally counterintuitive effects were found for the non-pigmented, UV reflecting nivea mutant: even though the overall reflectance intensity and UV signal of nivea flowers is several times that of wild type flowers, their detectability was significantly reduced relative to wild type flowers. In addition, naïve foragers preferred wild type flowers over nivea mutants, even though these generated a stronger signal in all receptor types. Our results show that single mutations affecting flower signal can have profound effects on pollinator behaviour—but not in ways predictable by crude assessments via human perception, nor simple quantification of UV signals. However, current models of bee visual perception predict the observed effects very well.

Arthropod-plant Interactions

13347986

10.1111/J.1469-8137.2010.03220.X

Birch (Betula spp.) leaves adsorb and re-release volatiles specific to neighbouring plants--a mechanism for associational herbivore resistance?

Plant-emitted semi-volatile compounds have low vaporization rates at 20-25 degrees C and may therefore persist on surfaces such as plant foliage. The passive adsorption of arthropod-repellent semi-volatiles to neighbouring foliage could convey associational resistance, whereby a plant's neighbours reduce damage caused by herbivores. We found that birch (Betula spp.) leaves adsorb and re-release the specific arthropod-repelling C(15) semi-volatiles ledene, ledol and palustrol produced by Rhododendron tomentosum when grown in mixed association in a field setup. In a natural habitat, a higher concentration of ledene was released from birches neighbouring R. tomentosum than from birches situated > 5 m from R. tomentosum. Emission of alpha-humulene, a sesquiterpene synthesized by both Betula pendula and R. tomentosum, was also increased in R. tomentosum-neighbouring B. pendula. In assessments for associational resistance, we found that the polyphagous green leaf weevils (Polydrusus flavipes) and autumnal moth (Epirrita autumnata) larvae both preferred B. pendula to R. tomentosum. P. flavipes also preferred birch leaves not exposed to R. tomentosum to leaves from mixed associations. In the field, a reduction in Euceraphis betulae aphid density occurred in mixed associations. Our results suggest that plant/tree species may be protected by semi-volatile compounds emitted by a more herbivore-resistant heterospecific neighbour.

New Phytologist

24611374

10.1023/A:1017506914063

Nitrogen retention in wetlands, lakes and rivers

As human activities continue to alter the global nitrogen cycle, the ability to predict the impact of increased nitrogen loading to freshwater systems is becoming more and more important. Nitrogen retention is of particular interest because it is through its combined processes (denitrification, nitrogen sedimentation and uptake by aquatic plants) that local and downstream nitrogen concentrations are reduced. Here, we compare the magnitude of nitrogen retention and its components in wetlands, lakes and rivers. We show that wetlands retain the highest proportion of total nitrogen loading, followed by lakes and then rivers. The differences in the proportion of N retained among systems is explained almost entirely by differences in water discharge. Denitrification is the primary mechanism of nitrogen retention, followed by nitrogen sedimentation and uptake by aquatic plants.

Hydrobiologia

4805345

10.1111/J.1469-8137.2011.04005.X

Genetic evidence for natural product-mediated plant-plant allelopathy in rice (Oryza sativa).

• There is controversy as to whether specific natural products play a role in directly mediating antagonistic plant-plant interactions - that is, allelopathy. If proved to exist, such phenomena would hold considerable promise for agronomic improvement of staple food crops such as rice (Oryza sativa). • However, while substantiated by the presence of phytotoxic compounds at potentially relevant concentrations, demonstrating a direct role for specific natural products in allelopathy has been difficult because of the chemical complexity of root and plant litter exudates. This complexity can be bypassed via selective genetic manipulation to ablate production of putative allelopathic compounds, but such an approach previously has not been applied. • The rice diterpenoid momilactones provide an example of natural products for which correlative biochemical evidence has been obtained for a role in allelopathy. Here, we apply reverse genetics, using knock-outs of the relevant diterpene synthases (copalyl diphosphate synthase 4 (OsCPS4) and kaurene synthase-like 4 (OsKSL4)), to demonstrate that rice momilactones are involved in allelopathy, including suppressing growth of the widespread rice paddy weed, barnyard grass (Echinochloa crus-galli). • Thus, our results not only provide novel genetic evidence for natural product-mediated allelopathy, but also furnish a molecular target for breeding and metabolic engineering of this important crop plant.

New Phytologist

1628191

10.1023/A:1006245605705

Can the ecosystem mimic hypotheses be applied to farms in African savannahs?

The first ecosystem mimic hypothesis suggests clear advantages if man-made land use systems do not deviate greatly in their resource use patterns from natural ecosystems typical of a given climatic zone. The second hypothesis claims that additional advantages will accrue if agroecosystems also maintain a substantial part of the diversity of natural systems. We test these hypotheses for the savannah zone of sub-Saharan Africa, with its low soil fertility and variable rainfall. Where annual food crops replace the natural grass understorey of savannah systems, water use will decrease and stream and groundwater flow change, unless tree density increases relative to the natural situation. Increasing tree density, however, will decrease crop yields, unless the trees meet specific criteria. Food crop production in the parkland systems may benefit from lower temperatures under tree canopies, but water use by trees providing this shade will prevent crops from benefiting. In old parkland trees that farmers have traditionally retained when opening fields for crops, water use per unit shade is less than in most fast growing trees introduced for agroforestry trials. Strong competition between plants adapted to years with different rainfall patterns may stabilise total system productivity -- but this will be appreciated by a farmer only if the components are of comparable value. The best precondition for farmers to maintain diversity in their agroecosystem hinges on the availability of a broad basket of choices, without clear winners or 'best bets'.

Agroforestry Systems

82771386

10.1016/BS.AIIP.2015.06.004

Evolution of the Mechanisms Underlying Insect Respiratory Gas Exchange

Abstract Many factors influence gas exchange patterns in insects and are generally treated in isolation from one another. Here, we provide a review of the current state of knowledge on the physics of gas exchange, insect respiratory chemoreceptors, the diversity and the methods typically used in the characterisation of respiratory pattern types, briefly covering some of the new tools and techniques that are being incorporated into this field. We then discuss the functional significance of insect gas exchange pattern variation, and possible evolutionary explanations of discontinuous gas exchange as a derived control mechanism for effecting physiological change in the context of (a) adaptive hypotheses, (b) non-adaptive hypotheses and (c) mathematical modelling of gas exchange. The lack of consensus in the literature for all proposed adaptive or mechanistic hypotheses suggests that multiple factors influence which gas exchange pattern is displayed by any particular insect during a given experiment. Thus, while the primary function of a breathing pattern is to meet an animal's gas exchange requirements, it is an interacting hierarchy of constraints that most likely determines how this demand may be met. We conclude the review with a brief discussion of future directions for the field.

Advances in Insect Physiology

5769057

10.1126/SCIENCE.1193210

A Biological Solution to a Fundamental Distributed Computing Problem

Modeling of development in the fruit fly yields an algorithm useful in designing wireless communication networks. Computational and biological systems are often distributed so that processors (cells) jointly solve a task, without any of them receiving all inputs or observing all outputs. Maximal independent set (MIS) selection is a fundamental distributed computing procedure that seeks to elect a set of local leaders in a network. A variant of this problem is solved during the development of the fly’s nervous system, when sensory organ precursor (SOP) cells are chosen. By studying SOP selection, we derived a fast algorithm for MIS selection that combines two attractive features. First, processors do not need to know their degree; second, it has an optimal message complexity while only using one-bit messages. Our findings suggest that simple and efficient algorithms can be developed on the basis of biologically derived insights.

Science

1941062

10.1073/PNAS.0408304102

Evidence for self-cleaning in gecko setae.

A tokay gecko can cling to virtually any surface and support its body mass with a single toe by using the millions of keratinous setae on its toe pads. Each seta branches into hundreds of 200-nm spatulae that make intimate contact with a variety of surface profiles. We showed previously that the combined surface area of billions of spatulae maximizes van der Waals interactions to generate large adhesive and shear forces. Geckos are not known to groom their feet yet retain their stickiness for months between molts. How geckos manage to keep their feet clean while walking about with sticky toes has remained a puzzle until now. Although self-cleaning by water droplets occurs in plant and animal surfaces, no adhesive has been shown to self-clean. In the present study, we demonstrate that gecko setae are a self-cleaning adhesive. Geckos with dirty feet recovered their ability to cling to vertical surfaces after only a few steps. Self-cleaning occurred in arrays of setae isolated from the gecko. Contact mechanical models suggest that self-cleaning occurs by an energetic disequilibrium between the adhesive forces attracting a dirt particle to the substrate and those attracting the same particle to one or more spatulae. We propose that the property of self-cleaning is intrinsic to the setal nanostructure and therefore should be replicable in synthetic adhesive materials in the future.

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

17679109

10.1242/JEB.034991

Ontogenetic changes in tracheal structure facilitate deep dives and cold water foraging in adult leatherback sea turtles

SUMMARY Adult leatherbacks are large animals (300–500 kg), overlapping in size with marine pinniped and cetacean species. Unlike marine mammals, they start their aquatic life as 40–50 g hatchlings, so undergo a 10,000-fold increase in body mass during independent existence. Hatchlings are limited to the tropics and near-surface water. Adults, obligate predators on gelatinous plankton, encounter cold water at depth (<1280 m) or high latitude and are gigantotherms that maintain elevated core body temperatures in cold water. This study shows that there are great ontogenetic changes in tracheal structure related to diving and exposure to cold. Hatchling leatherbacks have a conventional reptilian tracheal structure with circular cartilaginous rings interspersed with extensive connective tissue. The adult trachea is an almost continuous ellipsoidal cartilaginous tube composed of interlocking plates, and will collapse easily in the upper part of the water column during dives, thus avoiding pressure-related structural and physiological problems. It is lined with an extensive, dense erectile vascular plexus that will warm and humidify cold inspired air and possibly retain heat on expiration. A sub-luminal lymphatic plexus is also present. Mammals and birds have independently evolved nasal turbinates to fulfil such a respiratory thermocontrol function; for them, turbinates are regarded as diagnostic of endothermy. This is the first demonstration of a turbinate equivalent in a living reptile.

The Journal of Experimental Biology

25741471

10.1016/0021-9290(96)00001-2

Experimental and theoretical quantification of the development of damage in fatigue tests of bone and antler.

This study concerns the development of damage (as measured by a reduction in elastic modulus) in two kinds of bones differing considerably in their degrees of mineralisation: laminar bone from bovine femur and osteonal bone from red deer antler. Antler bone is much tougher than 'ordinary' bone and its failure properties have been investigated in: (i) monotonic tensile tests and (ii) creep rupture experiments. Tensile fatigue is another way of examining how damage develops in bone. The development of damage in the present fatigue tests was non-linear with the cycle number, the degree of non-linearity was dependent on the level of stress and followed a clearly different course for bone and antler. Antler was a more damage-tolerant material, being able to achieve a reduction in the final modulus of elasticity, just prior to failure, three times greater than 'ordinary' bone. The evolution of damage is quantified by an empirical and a graphical method and by the use of Continuum Damage Mechanics (CDM) expressions. The CDM method shows important conditions, found in antler, but not in bone, that seen necessary for achieving stable fractures and consequently producing very tough materials.

Journal of Biomechanics

47017314

10.1098/RSOS.171323

Structural design of the minute clypeasteroid echinoid Echinocyamus pusillus

The clypeasteroid echinoid skeleton is a multi-plated, light-weight shell construction produced by biomineralization processes. In shell constructions, joints between individual elements are considered as weak points, yet these echinoid skeletons show an extensive preservation potential in both Recent and fossil environments. The remarkable strength of the test is achieved by skeletal reinforcement structures and their constructional layouts. Micro-computed tomography and scanning electron microscopy are used for microstructural and volumetric analyses of the echinoid's skeleton. It is shown that strengthening mechanisms act on different hierarchical levels from the overall shape of the skeleton to skeletal interlocking. The tight-fitting and interlocking plate joints lead to a shell considered to behave as a monolithic structure. The plate's architecture features distinct regions interpreted as a significant load-transferring system. The internal support system follows the segmentation of the remaining skeleton, where sutural layout and stereom distribution are designed for effective load transfer. The structural analysis of the multi-plated, yet monolithic skeleton of Echinocyamus pusillus reveals new aspects of the micro-morphology and its structural relevance for the load-bearing behaviour. The analysed structural principles allow E. pusillus to be considered as a role model for the development of multi-element, light-weight shell constructions.

Royal Society Open Science

34506741

10.1073/PNAS.231471698

Attractive and defensive functions of the ultraviolet pigments of a flower (Hypericum calycinum)

The flower of Hypericum calycinum, which appears uniformly yellow to humans, bears a UV pattern, presumably visible to insects. Two categories of pigments, flavonoids and dearomatized isoprenylated phloroglucinols (DIPs), are responsible for the UV demarcations of this flower. Flavonoids had been shown previously to function as floral UV pigments, but DIPs had not been demonstrated to serve in that capacity. We found the DIPs to be present in high concentration in the anthers and ovarian wall of the flower, suggesting that the compounds also serve in defense. Indeed, feeding tests done with one of the DIPs (hypercalin A) showed the compound to be deterrent and toxic to a caterpillar (Utetheisa ornatrix). The possibility that floral UV pigments fulfill both a visual and a defensive function had not previously been contemplated. DIPs may also serve for protection of female reproductive structures in other plants, for example in hops (Humulus lupulus). The DIPs of hops are put to human use as bitter flavoring agents and preservatives in beer.

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

212748324

10.3389/FPLS.2020.00302

Fungal Aquaporins in Ectomycorrhizal Root Water Transport

Ectomycorrhizal fungi influence root water transport of host plants. To delineate the exact mechanisms of how fungal partner alters root water relations, it is important to understand the functions of fungal transmembrane water channels, i.e., aquaporins, the key component in the symplastic pathways. In this paper, we discussed what roles the fungal aquaporins may play in root water transport. We also highlighted the opportunities of using integrated approaches to address rising questions in future hotspots of aquaporin and root water relations research.

Frontiers in Plant Science

9510305

10.1016/J.CUB.2009.04.051

Conical Epidermal Cells Allow Bees to Grip Flowers and Increase Foraging Efficiency

The plant surface is by default flat, and development away from this default is thought to have some function of evolutionary advantage. Although the functions of many plant epidermal cells have been described, the function of conical epidermal cells, a defining feature of petals in the majority of insect-pollinated flowers, has not. The location and frequency of conical cells have led to speculation that they play a role in attracting animal pollinators. Snapdragon (Antirrhinum) mutants lacking conical cells have been shown to be discriminated against by foraging bumblebees. Here we investigated the extent to which a difference in petal surface structure influences pollinator behavior through touch-based discrimination. To isolate touch-based responses, we used both biomimetic replicas of petal surfaces and isogenic Antirrhinum lines differing only in petal epidermal cell shape. We show that foraging bumblebees are able to discriminate between different surfaces via tactile cues alone. We find that bumblebees use color cues to discriminate against flowers that lack conical cells--but only when flower surfaces are presented at steep angles, making them difficult to manipulate. This facilitation of physical handling is a likely explanation for the prevalence of conical epidermal petal cells in most flowering plants.

Current Biology

86811809

10.1093/MOLLUS/EYQ006

THE CALCAREOUS EGG CAPSULE OF THE PATAGONIAN NEOGASTROPOD ODONTOCYMBIOLA MAGELLANICA: MORPHOLOGY, SECRETION AND MINERALOGY

Odontocymbiola magellanica is the only known South American volutid gastropod that deposits calcareous egg capsules. The spawn is moulded and fixed to flat or convex surfaces by the female’s ventral pedal gland, during an hours-long process in which the female adopts a stereotyped posture and appears nonreactive to most external stimuli. Microscopically, the different cells of the ventral pedal gland show features suggesting their participation in the secretion of both the organic matrix and the calcium component of the calcareous layer. The latter consists mainly of numerous spherspherulites that are packed together around cylindrical, septated spaces which traverse the spherspherulitic layer and attach to the membranous layers surrounding the capsule cavity. These septated spaces should ensure permeability of the capsule wall, which is necessary for gas exchange and excretion by the embryo. The calcareous layer is made of high-magnesium calcite, a calcium carbonate polymorph in which Ca is partially substituted by Mg in the calcite lattice. Mg substitution is thought to confer a greater crack resistance to the mineral; it is found in many invertebrates, but apparently has not been reported before in molluscs. Odontocymbiola magellanica is a long-lived species, investing heavily in its egg capsules.

Journal of Molluscan Studies

1657537

10.1073/PNAS.0800966105

Extreme resistance of bdelloid rotifers to ionizing radiation

Rotifers of class Bdelloidea are common invertebrate animals with highly unusual characteristics, including apparently obligate asexuality, the ability to resume reproduction after desiccation at any life stage, and a paucity of transposable genetic elements of types not prone to horizontal transmission. We find that bdelloids are also extraordinarily resistant to ionizing radiation (IR). Reproduction of the bdelloids Adineta vaga and Philodina roseola is much more resistant to IR than that of Euchlanis dilatata, a rotifer belonging to the desiccation-intolerant and facultatively sexual class Monogononta, and all other animals for which we have found relevant data. By analogy with the desiccation- and radiation-resistant bacterium Deinococcus radiodurans, we suggest that the extraordinary radiation resistance of bdelloid rotifers is a consequence of their evolutionary adaptation to survive episodes of desiccation encountered in their characteristic habitats and that the damage incurred in such episodes includes DNA breakage that is repaired upon rehydration. Such breakage and repair may have maintained bdelloid chromosomes as colinear pairs and kept the load of transposable genetic elements low and may also have contributed to the success of bdelloid rotifers in avoiding the early extinction suffered by most asexuals.

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

14750972

10.1242/JEB.037861

Energy storage and synchronisation of hind leg movements during jumping in planthopper insects (Hemiptera, Issidae)

SUMMARY The hind legs of Issus (Hemiptera, Issidae) move in the same plane underneath the body, an arrangement that means they must also move synchronously to power jumping. Moreover, they move so quickly that energy must be stored before a jump and then released suddenly. High speed imaging and analysis of the mechanics of the proximal joints of the hind legs show that mechanical mechanisms ensure both synchrony of movements and energy storage. The hind trochantera move first in jumping and are synchronised to within 30 μs. Synchrony is achieved by mechanical interactions between small protrusions from each trochantera which fluoresce bright blue under specific wavelengths of ultra-violet light and which touch at the midline when the legs are cocked before a jump. In dead Issus, a depression force applied to a cocked hind leg, or to the tendon of its trochanteral depressor muscle causes a simultaneous depression of both hind legs. The protrusion of the hind leg that moves first nudges the other hind leg so that both move synchronously. Contractions of the trochanteral depressor muscles that precede a jump bend the metathoracic pleural arches of the internal skeleton. Large areas of these bow-shaped structures fluoresce bright blue in ultraviolet light, and the intensity of this fluorescence depends on the pH of the bathing saline. These are key signatures of the rubber-like protein resilin. The remainder of a pleural arch consists of stiff cuticle. Bending these composite structures stores energy and their recoil powers jumping.

The Journal of Experimental Biology

38574940

10.1016/0092-8674(90)90587-5

Rain-, wind-, and touch-induced expression of calmodulin and calmodulin-related genes in Arabidopsis

In response to water spray, subirrigation, wind, touch, wounding, or darkness, Arabidopsis regulates the expression of at least four touch-induced (TCH) genes. Ten to thirty minutes after stimulation, mRNA levels increase up to 100-fold. Arabidopsis plants stimulated by touch develop shorter petioles and bolts. This developmental response is known as thigmomorphogenesis. TCH 1 cDNA encodes the putative Arabidopsis calmodulin differing in one amino acid from wheat calmodulin. Sequenced regions of TCH 2 and TCH 3 contain 44% and 70% amino acid identities to calmodulin, respectively. The regulation of this calmodulin-related gene family in Arabidopsis suggests that calcium ions and calmodulin are involved in transduction of signals from the environment, enabling plants to sense and respond to environmental changes.

Cell

137342658

10.1016/S1672-6529(07)60010-9

Non-smooth morphologies of typical plant leaf surfaces and their anti-adhesion effects

The micromorphologies of surfaces of several typical plant leaves were investigated by scanning electron microscopy(SEM). Different non-smooth surface characteristics were described and classified. The hydrophobicity and anti-adhesion of non-smooth leaf surfaces were quantitatively measured. Results show that the morphology of epidermal cells and the morphology and distribution density of epicuticular wax directly affect the hydrophobicity and anti-adhesion. The surface with uniformly distributed convex units shows the best anti-adhesion, and the surface with regularly arranged trellis units displays better anti-adhesion. In contrast, the surface with randomly distributed hair units performs relatively bad anti-adhesion. The hydrophobic models of papilla-ciliary and fold-setal non-smooth surfaces were set up to determine the impacts of geometric parameters on the hydrophobicity. This study may provide an insight into surface machine molding and apparent morphology design for biomimetics engineering.

Journal of Bionic Engineering

85816907

10.2307/1540846

FISH MUCUS: IN SITU MEASUREMENTS OF POLYMER DRAG REDUCTION

The external layer of mucus on fish was investigated as a drag reducing polymer. Comparing velocity profiles for water flow over rainbow trout (Salmo gairdneri) and wax models of trout with and without hydrodynamically smooth surfaces revealed that the integumental mucous secretion can significantly reduce the rate of momentum transfer through the boundary layer. The difference in momentum transfer is expressed as a reduction in friction drag and discussed in view of the overall drag experienced by fish.

The Biological Bulletin

4382732

10.1038/NATURE13883

Passive radiative cooling below ambient air temperature under direct sunlight

Cooling is a significant end-use of energy globally and a major driver of peak electricity demand. Air conditioning, for example, accounts for nearly fifteen per cent of the primary energy used by buildings in the United States. A passive cooling strategy that cools without any electricity input could therefore have a significant impact on global energy consumption. To achieve cooling one needs to be able to reach and maintain a temperature below that of the ambient air. At night, passive cooling below ambient air temperature has been demonstrated using a technique known as radiative cooling, in which a device exposed to the sky is used to radiate heat to outer space through a transparency window in the atmosphere between 8 and 13 micrometres. Peak cooling demand, however, occurs during the daytime. Daytime radiative cooling to a temperature below ambient of a surface under direct sunlight has not been achieved because sky access during the day results in heating of the radiative cooler by the Sun. Here, we experimentally demonstrate radiative cooling to nearly 5 degrees Celsius below the ambient air temperature under direct sunlight. Using a thermal photonic approach, we introduce an integrated photonic solar reflector and thermal emitter consisting of seven layers of HfO2 and SiO2 that reflects 97 per cent of incident sunlight while emitting strongly and selectively in the atmospheric transparency window. When exposed to direct sunlight exceeding 850 watts per square metre on a rooftop, the photonic radiative cooler cools to 4.9 degrees Celsius below ambient air temperature, and has a cooling power of 40.1 watts per square metre at ambient air temperature. These results demonstrate that a tailored, photonic approach can fundamentally enable new technological possibilities for energy efficiency. Further, the cold darkness of the Universe can be used as a renewable thermodynamic resource, even during the hottest hours of the day.

Nature

25741145

10.1073/PNAS.0909872106

A nonprotein thermal hysteresis-producing xylomannan antifreeze in the freeze-tolerant Alaskan beetle Upis ceramboides

Thermal hysteresis (TH), a difference between the melting and freezing points of a solution that is indicative of the presence of large-molecular-mass antifreezes (e.g., antifreeze proteins), has been described in animals, plants, bacteria, and fungi. Although all previously described TH-producing biomolecules are proteins, most thermal hysteresis factors (THFs) have not yet been structurally characterized, and none have been characterized from a freeze-tolerant animal. We isolated a highly active THF from the freeze-tolerant beetle, Upis ceramboides, by means of ice affinity. Amino acid chromatographic analysis, polyacrylamide gel electrophoresis, UV-Vis spectrophotometry, and NMR spectroscopy indicated that the THF contained little or no protein, yet it produced 3.7 ± 0.3 °C of TH at 5 mg/ml, comparable to that of the most active insect antifreeze proteins. Compositional and structural analyses indicated that this antifreeze contains a β-mannopyranosyl-(1→4) β-xylopyranose backbone and a fatty acid component, although the lipid may not be covalently linked to the saccharide. Consistent with the proposed structure, treatment with endo-β-(1→4)xylanase ablated TH activity. This xylomannan is the first TH-producing antifreeze isolated from a freeze-tolerant animal and the first in a new class of highly active THFs that contain little or no protein.

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

7326296

10.1038/SREP11890

How ants use quorum sensing to estimate the average quality of a fluctuating resource

We show that one of the advantages of quorum-based decision-making is an ability to estimate the average value of a resource that fluctuates in quality. By using a quorum threshold, namely the number of ants within a new nest site, to determine their choice, the ants are in effect voting with their feet. Our results show that such quorum sensing is compatible with homogenization theory such that the average value of a new nest site is determined by ants accumulating within it when the nest site is of high quality and leaving when it is poor. Hence, the ants can estimate a surprisingly accurate running average quality of a complex resource through the use of extraordinarily simple procedures.

Scientific Reports

21244078

10.1098/RSPB.1981.0009

Desaturation of exhaled air in camels

We have found that camels can reduce the water loss due to evaporation from the respiratory tract in two ways: (1) by decreasing the temperature of the exhaled air and (2) by removal of water vapour from this air, resulting in the exhalation of air at less than 100% relative humidity (r. h.). Camels were kept under desert conditions and deprived of drinking water. In the daytime the exhaled air was at or near body core temperature, while in the cooler night exhaled air was at or near ambient air temperature. In the daytime the exhaled air was fully saturated, but at night its humidity might fall to approximately 75% r. h. The combination of cooling and desaturation can provide a saving of water of 60% relative to exhalation of saturated air at body temperature. The mechanism responsible for cooling of the exhaled air is a simple heat exchange between the respiratory air and the surfaces of the nasal passageways. On inhalation these surfaces are cooled by the air passing over them, and on exhalation heat from the exhaled air is given off to these cooler surfaces. The mechanism responsible for desaturation of the air appears to depend on the hygroscopic properties of the nasal surfaces when the camel is dehydrated. The surfaces give off water vapour during inhalation and take up water from the respiratory air during exhalation. We have used a simple mechanical model to demonstrate the effectiveness of this mechanism.

Proceedings of The Royal Society B: Biological Sciences

25806664

10.1002/JMOR.10232

Structural fiber reinforcement of keel blubber in harbor porpoise (Phocoena phocoena)

This study investigated the functional morphology of the blubber that forms the caudal keels of the harbor porpoise (Phocoena phocoena). Blubber is a pliant biocomposite formed by adipocytes and structural fibers composed of collagen and elastic fibers. Caudal keels are dorsally and ventrally placed triangular wedges of blubber that define the hydrodynamic profile of the porpoise tailstock. Mechanical tests on carcasses demonstrate that when keels are bent, they strain nonuniformly along their lengths, with highest strains just caudal to the dorsal fin and lowest at the insertion of the flukes. Therefore, caudal keels undergo nonuniform longitudinal deformation while maintaining a stable, triangular cross‐sectional shape. Polarizing and transmitted light microscopy techniques were used to investigate blubber's 3D fiber architecture along the length of the dorsal keel. The triangular cross‐sectional shape of the keel appears to be maintained by structural fibers oriented to act as tensile stays. The construction of the blubber composite is regionally specific :structural fiber densities and diameters are higher in the relatively stiff caudal region of the keel than in the more deformable cranial keel region. The orientations of structural fibers also change along the length of the keel. Cranially, no fibers are oriented along the long axis, whereas a novel population of longitudinally oriented fibers reinforces the keel at the insertion of the flukes. Thus, differences in the distribution and orientation of structural fibers contribute to the regionally specific mechanical properties of the dorsal keel. J. Morphol. 261:105–117, 2004. © 2004 Wiley‐Liss, Inc.

Journal of Morphology

21348778

10.1016/J.CBPB.2003.10.005

The ice worm, Mesenchytraeus solifugus, elevates adenylate levels at low physiological temperature.

The ice worm, Mesenchytraeus solifugus, is among a few metazoan species that survive exclusively in glacier ice/snow. In this study, we demonstrate that ice worm adenylate levels [i.e. adenosine 5'-triphosphate (ATP), ADP and AMP] are maintained at levels well above their mesophilic counterparts, and that their response to temperature change is distinctly opposite, namely, ice worms increase energy levels as temperatures fall. Initially, this response is characterized by a sharp spike in [ATP] and the adenylate energy charge (even at sub-zero temperatures), which is followed by corresponding increases in [ADP] and [AMP] within a few days. These results suggest that ice worms have evolved a compensatory mechanism by which gains in adenylate nucleotides off-set, at least in part, the inherent lethargy and death usually associated with cold temperature.

Comparative Biochemistry and Physiology A-molecular & Integrative Physiology

271974

10.1126/SCIENCE.2564698

Cnidocyte mechanoreceptors are tuned to the movements of swimming prey by chemoreceptors.

Cnidocytes, the stinging cells of cnidarians, discharge nematocysts in response to physical contact accompanied by the stimulation of specific chemoreceptors. Cnidocytes in fishing tentacles of a sea anemone are now found to discharge nematocysts preferentially into targets vibrating at 30, 55, and 65 to 75 hertz. Moreover, in the presence of submicromolar concentrations of known chemosensitizers, such as N-acetylated sugars and mucin, these optima shift to 5, 15, 30, and 40 hertz, frequencies that correspond to the movements of swimming prey. Hence, chemoreceptors for these substances tune cnidocyte mechanoreceptors to frequencies that match the movements of the prey.

Science

164450

10.1007/S10540-005-2887-4

Thermoregulation: What Role for UCPs in Mammals and Birds?

Mammals and birds are endotherms and respond to cold exposure by the means of regulatory thermogenesis, either shivering or non-shivering. In this latter case, waste of cell energy as heat can be achieved by uncoupling of mitochondrial respiration. Uncoupling proteins, which belong to the mitochondrial carrier family, are able to transport protons and thus may assume a thermogenic function. The mammalian UCP1 physiological function is now well understood and gives to the brown adipose tissue the capacity for heat generation. But is it really the case for its more recently discovered isoforms UCP2 and UCP3? Additionally, whereas more and more evidence suggests that non-shivering also exists in birds, is the avian UCP also involved in response to cold exposure? In this review, we consider the latest advances in the field of UCP biology and present putative functions for UCP1 homologues.

Bioscience Reports

42756257

10.1126/SCIENCE.1175553

Heat Exchange from the Toucan Bill Reveals a Controllable Vascular Thermal Radiator

Toucan Heat Exchanger Toucans are instantly recognizable by their large bills, which in the toco toucan (Ramphastos toco) accounts for about one-third of the total body length. The toucan's bill has been interpreted as a sexual ornament and as an adaptation for handling fruit. Tattersall et al. (p. 468) explore an alternative explanation in which the bill serves primarily as a thermoregulator. Infrared thermography techniques, which allow detailed observations with minimal disturbance to the birds, show that the birds alter blood flow to the bill according to ambient conditions, effectively using it as a radiator to “dump heat.” Toucans alter blood flow to their massive bills according to ambient conditions. The toco toucan (Ramphastos toco), the largest member of the toucan family, possesses the largest beak relative to body size of all birds. This exaggerated feature has received various interpretations, from serving as a sexual ornament to being a refined adaptation for feeding. However, it is also a significant surface area for heat exchange. Here we show the remarkable capacity of the toco toucan to regulate heat distribution by modifying blood flow, using the bill as a transient thermal radiator. Our results indicate that the toucan's bill is, relative to its size, one of the largest thermal windows in the animal kingdom, rivaling elephants’ ears in its ability to radiate body heat.

Science

17475715

10.1007/S00435-012-0165-0

Revisiting a medical case of “stinging” in the human oral cavity caused by ingestion of raw squid (Cephalopoda: Teuthida): new data on the functioning of squid’s spermatophores

Male squid produce intricate spermatophores that, when transferred to the female, undergo the spermatophoric reaction, a complex process of evagination that leads to the attachment of the spermatangium, that is, the everted spermatophore containing the sperm mass. While this process is still not completely understood, the medical literature includes several reports of “oral stinging” (i.e., punctured wounds in the human oral cavity) following consumption of raw male squid, which contains undischarged spermatophores able to inflict such wounds. Here, we revisit a recent medical report of oral stinging by Shiraki et al. (Pathol Int 61:749–751, 2011), providing an in-depth reanalysis of their histological biopsies and revealing vital information on the functioning of squid spermatophores. The morphology of the spermatangia attached within the oral cavity is similar to the condition found in spermatangia naturally attached to female squids. The spermatangia were able to superficially puncture the superficial layers of the oral stratified squamous epithelium, and numerous, minute stellate particles from the squid spermatophore were found adhered to the oral epithelium. These findings corroborate previous hypotheses on the functioning of squid spermatophores, namely that spermatophore attachment generally involves tissue scarification, and that stellate particles play a vital role in the attachment process. Moreover, spermatophore attachment is confirmed to be autonomous (i.e., performed by the spermatophore itself) in another squid species (possibly a loliginid), and the results strongly indicate that the attachment mechanism is not dependent upon a specialized epithelium, nor a mate’s specific chemical stimulus. From the pathological point of view, the best prophylactic measure at present is the removal of the internal organs of the raw squid prior to its consumption.

Zoomorphology

4327745

10.1038/NATURE04588

An excitable gene regulatory circuit induces transient cellular differentiation

Certain types of cellular differentiation are probabilistic and transient. In such systems individual cells can switch to an alternative state and, after some time, switch back again. In Bacillus subtilis, competence is an example of such a transiently differentiated state associated with the capability for DNA uptake from the environment. Individual genes and proteins underlying differentiation into the competent state have been identified, but it has been unclear how these genes interact dynamically in individual cells to control both spontaneous entry into competence and return to vegetative growth. Here we show that this behaviour can be understood in terms of excitability in the underlying genetic circuit. Using quantitative fluorescence time-lapse microscopy, we directly observed the activities of multiple circuit components simultaneously in individual cells, and analysed the resulting data in terms of a mathematical model. We find that an excitable core module containing positive and negative feedback loops can explain both entry into, and exit from, the competent state. We further tested this model by analysing initiation in sister cells, and by re-engineering the gene circuit to specifically block exit. Excitable dynamics driven by noise naturally generate stochastic and transient responses, thereby providing an ideal mechanism for competence regulation.

Nature

19891704

10.1242/JEB.006189

The contribution of mineral to the material properties of vertebral cartilage from the smooth-hound shark Mustelus californicus

SUMMARY Elasmobranch vertebral cartilage has a substantial mineral fraction (39–55%) and the arrangement of mineral varies among species. We examined vertebrae from one shark species, Mustelus californicus, to determine mineral content, the effect of mineral on material properties and the viscoelastic response of vertebral cartilage. We serially demineralized vertebrae and compressively tested them to failure at varying strain rates. Mineral in vertebral cartilage varies within individuals, intraspecifically and interspecifically; this is in contrast to bone, in which significant variation in mineral content is pathological or an interspecific effect. Within Mustelus, vertebrae with larger mineral fractions were significantly stiffer and stronger; however when variation is assessed across species, the structure has a larger effect. Shark vertebral cartilage did not show a substantial viscoelastic response at biologically relevant strain rates, validating the use of quasistatic testing for this material.

The Journal of Experimental Biology

87696073

10.2307/1446299

Permeability and Water Relations of Hygroscopic Skin of the File Snake, Acrochordus granulatus

Copeia

30035963

10.1016/J.MIB.2013.01.003

Exploiting social evolution in biofilms.

Bacteria are highly social organisms that communicate via signaling molecules, move collectively over surfaces and make biofilm communities. Nonetheless, our main line of defense against pathogenic bacteria consists of antibiotics-drugs that target individual-level traits of bacterial cells and thus, regrettably, select for resistance against their own action. A possible solution lies in targeting the mechanisms by which bacteria interact with each other within biofilms. The emerging field of microbial social evolution combines molecular microbiology with evolutionary theory to dissect the molecular mechanisms and the evolutionary pressures underpinning bacterial sociality. This exciting new research can ultimately lead to new therapies against biofilm infections that exploit evolutionary cheating or the trade-off between biofilm formation and dispersal.

Current Opinion in Microbiology

4247313

10.1038/176657A0

Lunar Rhythm in the Emergence of an Ephemeropteran

IN a paper published in 1927, Hora1 suggests that the swarming of some Ephemeroptera is related to the lunar cycle. Evidence has been obtained which suggests that Povilla adusta Navas, a mayfly widely distributed in Central and Southern Africa, shows such a rhythm of emergence in Uganda. The interest of this lies in the fact that very few examples are known of lunar rhythms in non-marine animals (see Gaspers2).

Nature

786330

10.1371/JOURNAL.PCBI.1002894

Starling Flock Networks Manage Uncertainty in Consensus at Low Cost

Flocks of starlings exhibit a remarkable ability to maintain cohesion as a group in highly uncertain environments and with limited, noisy information. Recent work demonstrated that individual starlings within large flocks respond to a fixed number of nearest neighbors, but until now it was not understood why this number is seven. We analyze robustness to uncertainty of consensus in empirical data from multiple starling flocks and show that the flock interaction networks with six or seven neighbors optimize the trade-off between group cohesion and individual effort. We can distinguish these numbers of neighbors from fewer or greater numbers using our systems-theoretic approach to measuring robustness of interaction networks as a function of the network structure, i.e., who is sensing whom. The metric quantifies the disagreement within the network due to disturbances and noise during consensus behavior and can be evaluated over a parameterized family of hypothesized sensing strategies (here the parameter is number of neighbors). We use this approach to further show that for the range of flocks studied the optimal number of neighbors does not depend on the number of birds within a flock; rather, it depends on the shape, notably the thickness, of the flock. The results suggest that robustness to uncertainty may have been a factor in the evolution of flocking for starlings. More generally, our results elucidate the role of the interaction network on uncertainty management in collective behavior, and motivate the application of our approach to other biological networks.

PLOS Computational Biology

2457274

10.1007/S00359-005-0063-8

Immunochemical and electrophysiological analyses of magnetically responsive neurons in the mollusc Tritonia diomedea

Tritonia diomedea uses the Earth’s magnetic field as an orientation cue, but little is known about the neural mechanisms that underlie magnetic orientation behavior in this or other animals. Six large, individually identifiable neurons in the brain of Tritonia (left and right Pd5, Pd6, Pd7) are known to respond with altered electrical activity to changes in earth-strength magnetic fields. In this study we used immunochemical, electrophysiological, and neuroanatomical techniques to investigate the function of the Pd5 neurons, the largest magnetically responsive cells. Immunocytochemical studies localized TPeps, neuropeptides isolated from Pd5, to dense-cored vesicles within the Pd5 somata and within neurites adjacent to ciliated foot epithelial cells. Anatomical analyses revealed that neurites from Pd5 are located within nerves innervating the ipsilateral foot and body wall. These results imply that Pd5 project to the foot and regulate ciliary beating through paracrine release. Electrophysiological recordings indicated that, although both LPd5 and RPd5 responded to the same magnetic stimuli, the pattern of spiking in the two cells differed. Given that TPeps increase ciliary beating and Tritonia locomotes using pedal cilia, our results are consistent with the hypothesis that Pd5 neurons control or modulate the ciliary activity involved in crawling during orientation behavior.

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

43736046

10.1126/SCIENCE.1147455

Mutual Feedbacks Maintain Both Genetic and Species Diversity in a Plant Community

The forces that maintain genetic diversity among individuals and diversity among species are usually studied separately. Nevertheless, diversity at one of these levels may depend on the diversity at the other. We have combined observations of natural populations, quantitative genetics, and field experiments to show that genetic variation in the concentration of an allelopathic secondary compound in Brassica nigra is necessary for the coexistence of B. nigra and its competitor species. In addition, the diversity of competing species was required for the maintenance of genetic variation in the trait within B. nigra. Thus, conservation of species diversity may also necessitate maintenance of the processes that sustain the genetic diversity of each individual species.

Science

2708997

10.1098/RSPB.2010.1739

Moving calls: a vocal mechanism underlying quorum decisions in cohesive groups

Members of social groups need to coordinate their behaviour when choosing between alternative activities. Consensus decisions enable group members to maintain group cohesion and one way to reach consensus is to rely on quorums. A quorum response is where the probability of an activity change sharply increases with the number of individuals supporting the new activity. Here, we investigated how meerkats (Suricata suricatta) use vocalizations in the context of movement decisions. Moving calls emitted by meerkats increased the speed of the group, with a sharp increase in the probability of changing foraging patch when the number of group members joining the chorus increased from two up to three. These calls had no apparent effect on the group's movement direction. When dominant individuals were involved in the chorus, the group's reaction was not stronger than when only subordinates called. Groups only increased speed in response to playbacks of moving calls from one individual when other group members emitted moving calls as well. The voting mechanism linked to a quorum probably allows meerkat groups to change foraging patches cohesively with increased speed. Such vocal coordination may reflect an aggregation rule linking individual assessment of foraging patch quality to group travel route.

Proceedings of The Royal Society B: Biological Sciences

28691651

10.1073/PNAS.0604972103

An exceptionally fast actomyosin reaction powers insect flight muscle

Insects, as a group, have been remarkably successful in adapting to a great range of physical and biological environments, in large part because of their ability to fly. The evolution of flight in small insects was accompanied by striking adaptations of the thoracic musculature that enabled very high wing beat frequencies. At the cellular and protein filament level, a stretch activation mechanism evolved that allowed high-oscillatory work to be achieved at very high frequencies as contraction and nerve stimulus became asynchronous. At the molecular level, critical adaptations occurred within the motor protein myosin II, because its elementary interactions with actin set the speed of sarcomere contraction. Here, we show that the key myosin enzymatic adaptations required for powering the very fast flight muscles in the fruit fly Drosophila melanogaster include the highest measured detachment rate of myosin from actin (forward rate constant, 3,698 s−1), an exceptionally weak affinity of MgATP for myosin (association constant, 0.2 mM−1), and a unique rate-limiting step in the cross-bridge cycle at the point of inorganic phosphate release. The latter adaptations are constraints imposed by the overriding requirement for exceptionally fast release of the hydrolytic product MgADP. Otherwise, as in Drosophila embryonic muscle and other slow muscle types, a step associated with MgADP release limits muscle contraction speed by delaying the detachment of myosin from actin.

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

25086522

10.1104/PP.114.3.789

Cytoplasmic Free Ca2+ in Arabidopsis Roots Changes in Response to Touch but Not Gravity

Changes in cytoplasmic Ca2+ concentration ([Ca2+]i) have been proposed to be involved in signal transduction pathways in response to a number of stimuli, including gravity and touch. The current hypothesis proposes that the development of gravitropic bending is correlated with a redistribution of [Ca2+]i in gravistimulated roots. However, no study has demonstrated clearly the development of an asymmetry of this ion during root curvature. We tested this hypothesis by quantifying the temporal and spatial changes in [Ca2+]i in roots of living Arabidopsis seedlings using ultraviolet-confocal Ca2+-ratio imaging and vertical stage fluorescence microscopy to visualize root [Ca2+]i. We observed no changes in [Ca2+]i associated with the graviresponse whether monitored at the whole organ level or in individual cells in different regions of the root for up to 12 h after gravistimulation. However, touch stimulation led to transient increases in [Ca2+]i in all cell types monitored. The increases induced in the cap cells were larger and longer-lived than in cells in the meristematic or elongation zone. One millimolar La3+ and 100 [mu]M verapamil did not prevent these responses, whereas 5 mM EGTA or 50 [mu]M ruthenium red inhibited the transients, indicating an intracellular origin of the Ca2+ increase. These results suggest that, although touch responses of roots may be mediated through a Ca2+-dependent pathway, the gravitropic response is not associated with detectable changes in [Ca2+]i.

Plant Physiology

15045354

10.1371/JOURNAL.PONE.0051803

Unique Structural Features Facilitate Lizard Tail Autotomy

Autotomy refers to the voluntary shedding of a body part; a renowned example is tail loss among lizards as a response to attempted predation. Although many aspects of lizard tail autotomy have been studied, the detailed morphology and mechanism remains unclear. In the present study, we showed that tail shedding by the Tokay gecko (Gekko gecko) and the associated extracellular matrix (ECM) rupture were independent of proteolysis. Instead, lizard caudal autotomy relied on biological adhesion facilitated by surface microstructures. Results based on bio-imaging techniques demonstrated that the tail of Gekko gecko was pre-severed at distinct sites and that its structural integrity depended on the adhesion between these segments.

PLOS ONE

2514713

10.1098/RSPB.2011.1840

Variation in annual and lifetime reproductive success of lance-tailed manakins: alpha experience mitigates effects of senescence on siring success

The causes of variation in individual reproductive success over a lifetime are not well understood. In long-lived vertebrates, reproductive output usually increases during early adulthood, but it is difficult to disentangle the roles of development and learning on this gain of reproductive success. Lekking lance-tailed manakins provide an opportunity to separate these processes, as the vast majority of male reproduction occurs after a bird obtains alpha status and maintains a display area in the lek, but the age at which males achieve alpha status varies widely. Using 11 years of longitudinal data on age, social status and genetic siring success, I assessed the factors influencing variation in siring success by individuals over their lifetimes. The data show increases in annual reproductive success with both age and alpha experience. At advanced ages, these gains were offset by senescence in fecundity. Individual ontogeny, rather than compositional change of the population, generated a nonlinear relationship of breeding tenure with lifetime success; age of assuming alpha status was unrelated to tenure as a breeder, or success in the alpha role. Importantly, these findings suggest that social experience can mitigate the negative effects of senescence in older breeders.

Proceedings of The Royal Society B: Biological Sciences

53195856

10.1016/J.ANBEHAV.2011.02.030

Resolution of experimentally induced symmetrical conflicts of interest in meerkats

Changes in activity in animal groups are a potential source of group fragmentation if members do not coordinate themselves. This coordination can become further complicated when individuals within a group face conflicts of interest. We experimentally induced symmetrical conflicts of interest over which direction to choose in meerkat, Suricata suricatta, groups. We trained dominant and subordinate individuals to expect food at locations in opposite directions when the group was still at its sleeping burrow (i.e. before the group started foraging). Trained individuals were more likely to initiate group departure in the direction of their rewarded location and there was no difference between dominants and subordinates in initiation rate. Initiation of group departure seemed to be the most important factor determining the final direction of the group, as the direction chosen by the first initiator was rarely challenged. We did not observe any obvious signals used to enhance recruitment during this process. Over the experimental days, initiator identity changed suggesting that individual motivation to initiate group departure varies from day to day. Meerkats voluntarily avoided immediate foraging benefits to maintain cohesion with the group, which probably prevented them from incurring costs associated with becoming isolated. We conclude that individuals refrain from initiating group splits when conflicts of interest are low and any individual can take the lead, often without the use of obvious signals other than the displacement itself.

Animal Behaviour

2316676

10.1021/LA061622M

Wetting properties of the multiscaled nanostructured polymer and metallic superhydrophobic surfaces.

A superhydrophobic surface is produced from industrial grade polymer materials. The surface comprises partly disordered triple-scaled arrays of polyvinylidene fluoride (PVDF) globules. An inherently superhydrophobic metallic surface is produced with polymer template. The mathematical model based on the Cassie-Baxter hypothesis of air trapping under a water drop is built, which gives the apparent contact angle on the manifold-scaled interface. The presence of several scales itself is not a sufficient condition of hydrophobicity of inherently wettable surfaces. The geometrical features favoring the increase of the vapor-water interface fraction are necessary for this phenomenon.

Langmuir

36992016

10.1023/A:1006243032538

Why tree-crop interactions in agroforestry appear at odds with tree-grass interactions in tropical savannahs

This paper describes recent research findings on resource sharing between trees and crops in the semiarid tropics and attempts to reconcile this information with current knowledge of the interactions between savannah trees and understorey vegetation by examining agroforestry systems from the perspective of succession. In general, productivity of natural vegetation under savannah trees increases as rainfall decreases, while the opposite occurs in agroforestry. One explanation is that in the savannah, the beneficial effects of microclimatic improvements (e.g. lower temperatures and evaporation losses) are greater in more xeric environments. Mature savannah trees have a high proportion of woody above-ground structure compared to foliage, so that the amount of water 'saved' (largely by reduction in soil evaporation) is greater than water 'lost' through transpiration by trees. By contrast, in agroforestry practices such as alley cropping where tree density is high, any beneficial effects of the trees on microclimate are negated by reductions in soil moisture due to increasing interception losses and tree transpiration. While investment in woody structure can improve the water economy beneath agroforestry trees, it inevitably reduces the growth rate of the trees and thus increases the time required for improved understorey productivity. Therefore, agroforesters prefer trees with more direct and immediate benefits to farmers. The greatest opportunity for simultaneous agroforestry practices is therefore to fill niches within the landscape where resources are currently under-utilised by crops. In this way, agroforestry can mimic the large scale patch dynamics and successional progression of a natural ecosystem.

Agroforestry Systems

3664412

10.1038/NRMICRO.2018.10

Bacterial microcompartments

Bacterial microcompartments (BMCs) are self-assembling organelles that consist of an enzymatic core that is encapsulated by a selectively permeable protein shell. The potential to form BMCs is widespread and found across the kingdom Bacteria. BMCs have crucial roles in carbon dioxide fixation in autotrophs and the catabolism of organic substrates in heterotrophs. They contribute to the metabolic versatility of bacteria, providing a competitive advantage in specific environmental niches. Although BMCs were first visualized more than 60 years ago, it is mainly in the past decade that progress has been made in understanding their metabolic diversity and the structural basis of their assembly and function. This progress has not only heightened our understanding of their role in microbial metabolism but is also beginning to enable their use in a variety of applications in synthetic biology. In this Review, we focus on recent insights into the structure, assembly, diversity and function of BMCs.

Microporous and Mesoporous Materials; Annual Review of Microbiology

23576925

10.1073/PNAS.0409574102

Hydrogen and bioenergetics in the Yellowstone geothermal ecosystem.

The geochemical energy budgets for high-temperature microbial ecosystems such as occur at Yellowstone National Park have been unclear. To address the relative contributions of different geochemistries to the energy demands of these ecosystems, we draw together three lines of inference. We studied the phylogenetic compositions of high-temperature (>70 degrees C) communities in Yellowstone hot springs with distinct chemistries, conducted parallel chemical analyses, and carried out thermodynamic modeling. Results of extensive molecular analyses, taken with previous results, show that most microbial biomass in these systems, as reflected by rRNA gene abundance, is comprised of organisms of the kinds that derive energy for primary productivity from the oxidation of molecular hydrogen, H2. The apparent dominance by H2-metabolizing organisms indicates that H2 is the main source of energy for primary production in the Yellowstone high-temperature ecosystem. Hydrogen concentrations in the hot springs were measured and found to range up to >300 nM, consistent with this hypothesis. Thermodynamic modeling with environmental concentrations of potential energy sources also is consistent with the proposed microaerophilic, hydrogen-based energy economy for this geothermal ecosystem, even in the presence of high concentrations of sulfide.

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

14331051

10.1242/JEB.035550

Venom kinematics during prey capture in Conus: the biomechanics of a rapid injection system

SUMMARY Cone snails use an extensile, tubular proboscis as a conduit to deliver a potent cocktail of bioactive venom peptides into their prey. Previous studies have focused mainly on understanding the venom's role in prey capture but successful prey capture requires both rapid physiological and biomechanical mechanisms. Conus catus, a fish-hunting species, uses a high-speed hydraulic mechanism to inject its hollow, spear-like radular tooth into prey. We take an integrated approach to investigating the biomechanics of this process by coupling kinematic studies with morphological analyses. Taking advantage of the opaque venom and translucent proboscis of a mollusc-hunting juvenile cone snail, Conus pennaceus, we have determined that a high-speed prey capture mechanism is not unique to cone species that hunt fish prey. Two morphological structures were found to play crucial roles in this process. A constriction of the lumen near the tip of the proboscis, composed of tall epithelial cells densely packed with microfilaments, impedes forward movement of the radular tooth prior to its propulsion. Proximal to the constriction, a muscular sphincter was found to regulate venom flow and pressurization in the proboscis. In C. pennaceus, the rapid appearance and flushing of venom within the proboscis during prey capture suggests a mechanism involving the delivery of a discrete quantity of venom. The interplay between these elements provides a unique and effective biomechanical injection system for the fast-acting cone snail venom peptides.

The Journal of Experimental Biology

84501542

10.2307/2399893

A Systematic Revision of Adansonia (Bombacaceae)

Annals of the Missouri Botanical Garden

9942631

10.1093/BIOINFORMATICS/BTM400

Metal reduction kinetics in Shewanella

MOTIVATION Metal reduction kinetics have been studied in cultures of dissimilatory metal reducing bacteria which include the Shewanella oneidensis strain MR-1. Estimation of system parameters from time-series data faces obstructions in the implementation depending on the choice of the mathematical model that captures the observed dynamics. The modeling of metal reduction is often based on Michaelis-Menten equations. These models are often developed using initial in vitro reaction rates and seldom match with in vivo reduction profiles. RESULTS For metal reduction studies, we propose a model that is based on the power law representation that is effectively applied to the kinetics of metal reduction. The method yields reasonable parameter estimates and is illustrated with the analysis of time-series data that describes the dynamics of metal reduction in S.oneidensis strain MR-1. In addition, mixed metal studies involving the reduction of Uranyl (U(VI)) to the relatively insoluble tetravalent form (U(IV)) by S. alga strain (BR-Y) were studied in the presence of environmentally relevant iron hydrous oxides. For mixed metals, parameter estimation and curve fitting are accomplished with a generalized least squares formulation that handles systems of ordinary differential equations and is implemented in Matlab. It consists of an optimization algorithm (Levenberg-Marquardt, LSQCURVEFIT) and a numerical ODE solver. Simulation with the estimated parameters indicates that the model captures the experimental data quite well. The model uses the estimated parameters to predict the reduction rates of metals and mixed metals at varying concentrations. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.

Bioinformatics

31922146

10.1007/BF00344858

Irregular fog as a water source for desert dune beetles

SummaryThree methods of fog-water uptake have been observed in three tribes of Namib desert dune tenebrionid beetles, Adesmiini, Eurychorini and Zophosini. The methods used correlate with distribution and gross morphology of each species but cut across phylogenetic affinities. Of the three methods described, none involve obvious fine anatomical or physical adaptations of the beetles for fog-water uptake. Rather, the beetles have evolved specific behavioural patterns for drinking water condensed on vegetation, their own dorsum or sand.Use of fog-water necessitates surface activity at times when surface temperatures and wind velocities are not optimal for these diurnal or crepuscular species. Behavioural adaptation has enabled these beetles to use irregular and unpredictable fogs as a moisture source.

Oecologia

8059321

10.1126/SCIENCE.1079354

Genetic Control of Surface Curvature

Although curvature of biological surfaces has been considered from mathematical and biophysical perspectives, its molecular and developmental basis is unclear. We have studied the cinmutant of Antirrhinum, which has crinkly rather than flat leaves. Leaves of cin display excess growth in marginal regions, resulting in a gradual introduction of negative curvature during development. This reflects a change in the shape and the progression of a cell-cycle arrest front moving from the leaf tip toward the base. CIN encodes a TCP protein and is expressed downstream of the arrest front. We propose that CIN promotes zero curvature (flatness) by making cells more sensitive to an arrest signal, particularly in marginal regions.

Science

83984216

10.1016/0022-1910(88)90126-6

Water balance and osmoregulation in Physadesmia globosa, a diurnal tenebrionid beetle from the Namib desert

Abstract Dehydration (10 days at 26°C) of the Namib tenebrionid beetle Physadesmia globosa resulted in rapid weight loss (approx. 19%), and a substantial decline in haemolymph volume (61%). Although the lipid content decreased significantly during this period, metabolic water production was insufficient to maintain total body water. Rehydration (no food) resulted in increases in body weight and haemolymph volume (sub-normal), and total body water to normality. Haemolymph osmolality, sodium, potassium and chloride concentrations increased during dehydration, but despite a marked decrease in the volume of haemolymph, changes in these parameters were subject to osmoregulatory control. Protein concentrations increased during dehydration and decreased during rehydration. Rapid rehydration (1 h) is well-controlled: while haemolymph volume increased dramatically, haemolymph osmolality, sodium, potassium and chloride were strongly regulated. However, extended rehydration (over 4 days) appears not to be as well managed by Physadesmia, with haemolymph osmolality and sodium concentrations decreasing despite no significant change in haemolymph volume from immediate post-rehydration (1 h) values. The potassium and chloride concentrations, however, appeared to be under stricter control during this period. Drinking (when fog water is available) probably contributes largely to the total water input of Physadesmia, and this together with efficient water conservation must serve to maintain effectively long-term water balance in these insects.

Journal of Insect Physiology

32093393

10.1016/S0960-0779(99)00122-8

The influence of stochastic behavior on the human threshold of hearing

Abstract The inner hair cells in the cochlea perform the crucial task of transforming mechanical sound signals into electrical activity. The cochlear nerve fibers code this information and convey it to the brain for further processing. This study investigates the performance of the system inner hair cell – primary auditory afferent nerve fibers at the physical limit of the mechano-electrical transduction for the human auditory frequency range. The Brownian motion of the hair cell’s receptive organelle, the hair bundle, does not blunt the sensitivity, but in fact enlarges – especially in frequency regions which are most important for the perception of music and speech – via the mechanism of nonlinear stochastic resonance (SR) the dynamical range of the mechano-electrical transduction by at least one order of magnitude. The coding efficiency of small sinusoidal hair bundle deflections shows basic properties of the human hearing threshold curve for pure tones and corresponds to experimental results of noise-induced tuning curves in mechano-receptors in the rat foot. Furthermore, the model explains how altered coding efficiency contributes to pathological changes in the spiking pattern which arise from morphological changes in the hair bundle structure (e.g., in noise-induced sensorineural hearing loss of cochlear origin).

Chaos Solitons & Fractals

35082791

10.1007/S00265-010-0911-6

Sensory allometry, foraging task specialization and resource exploitation in honeybees

Insect societies are important models for evolutionary biology and sociobiology. The complexity of some eusocial insect societies appears to arise from self-organized task allocation and group cohesion. One of the best-supported models explaining self-organized task allocation in social insects is the response threshold model, which predicts specialization due to inter-individual variability in sensitivity to task-associated stimuli. The model explains foraging task specialization among honeybee workers, but the factors underlying the differences in individual sensitivity remain elusive. Here, we propose that in honeybees, sensory sensitivity correlates with individual differences in the number of sensory structures, as it does in solitary species. Examining European and Africanized honeybees, we introduce and test the hypothesis that body size and/or sensory allometry is associated with foraging task preferences and resource exploitation. We focus on common morphological measures and on the size and number of structures associated with olfactory sensitivity. We show that the number of olfactory sensilla is greater in pollen and water foragers, which are known to exhibit higher sensory sensitivity, compared to nectar foragers. These differences are independent of the distribution of size within a colony. Our data also suggest that body mass and number of olfactory sensilla correlate with the concentration of nectar gathered by workers, and with the size of pollen loads they carry. We conclude that sensory allometry, but not necessarily body size, is associated with resource exploitation in honeybees and that the differences in number of sensilla may underlie the observed differences in sensitivity between bees specialized on water, pollen and nectar collection.

Behavioral Ecology and Sociobiology

4373308

10.1038/NATURE10245

Ganglion-specific splicing of TRPV1 underlies infrared sensation in vampire bats

Vampire bats (Desmodus rotundus) are obligate blood feeders that have evolved specialized systems to suit their sanguinary lifestyle. Chief among such adaptations is the ability to detect infrared radiation as a means of locating hotspots on warm-blooded prey. Among vertebrates, only vampire bats, boas, pythons and pit vipers are capable of detecting infrared radiation. In each case, infrared signals are detected by trigeminal nerve fibres that innervate specialized pit organs on the animal’s face. Thus, vampire bats and snakes have taken thermosensation to the extreme by developing specialized systems for detecting infrared radiation. As such, these creatures provide a window into the molecular and genetic mechanisms underlying evolutionary tuning of thermoreceptors in a species-specific or cell-type-specific manner. Previously, we have shown that snakes co-opt a non-heat-sensitive channel, vertebrate TRPA1 (transient receptor potential cation channel A1), to produce an infrared detector. Here we show that vampire bats tune a channel that is already heat-sensitive, TRPV1, by lowering its thermal activation threshold to about 30 °C. This is achieved through alternative splicing of TRPV1 transcripts to produce a channel with a truncated carboxy-terminal cytoplasmic domain. These splicing events occur exclusively in trigeminal ganglia, and not in dorsal root ganglia, thereby maintaining a role for TRPV1 as a detector of noxious heat in somatic afferents. This reflects a unique organization of the bat Trpv1 gene that we show to be characteristic of Laurasiatheria mammals (cows, dogs and moles), supporting a close phylogenetic relationship with bats. These findings reveal a novel molecular mechanism for physiological tuning of thermosensory nerve fibres.

Nature

5081700

10.1242/JEB.01509

Propulsive force calculations in swimming frogs I. A momentum–impulse approach

SUMMARY Frogs are animals that are capable of locomotion in two physically different media, aquatic and terrestrial. A comparison of the kinematics of swimming frogs in a previous study revealed a difference in propulsive impulse between jumping and swimming. To explore this difference further, we determined the instantaneous forces during propulsion in swimming using an impulse–momentum approach based on DPIV flow data. The force profile obtained was compared with force profiles obtained from drag–thrust equilibrium of the centre of mass and with the force profiles generated during jumping. The new approach to quantifying the instantaneous forces during swimming was tested and proved to be a valid method for determining the external forces on the feet of swimming frogs. On the kinematic profiles of swimming, leg extension precedes propulsion. This means that it is not only the acceleration of water backwards that provides thrust, but also that the deceleration of water flowing towards the frog as a result of recovery accelerates the centre of mass prior to leg extension. The force profile obtained from the impulse–momentum approach exposed an overestimation of drag by 30% in the drag–thrust calculations. This means that the difference in impulse between jumping and swimming in frogs is even larger than previously stated. The difference between the force profiles, apart from a slightly higher peak force during jumping, lies mainly in a difference in shape. During swimming, maximal force is reached early in the extension phase, 20% into it, while during jumping, peak force is attained at 80% of the extension phase. This difference is caused by a difference in inter-limb coordination.

The Journal of Experimental Biology

37620009

10.1007/S00049-011-0077-3

Congruence of epicuticular hydrocarbons and tarsal secretions as a principle in beetles

Within beetles, those species that are adapted to life on plants have developed widened tarsi with specialised hairy attachment structures. The capability to adhere to smooth surfaces is based on a liquid film on the surface of these structures, the composition of which is similar to the cuticular lipids. By means of a cluster analysis based on chemical similarities between samples obtained from tarsi or elytra of 35 species using solid phase microextraction, the present study strongly suggests that this chemical congruence is a principle in beetles. This supports the idea of tarsal liquids being part of the cuticular lipid layer and contributes to the understanding of liquid-mediated attachment systems.

Chemoecology

206695622

10.1126/STKE.117PE17

Notch Signaling in Osteoblasts

Bone remodeling is the result of the coordinated activity of osteoblasts, which form new matrix, and osteoclasts, which resorb bone. Notch proteins are single-pass transmembrane receptors that determine cell fate. Recent gain-of-function and loss-of-function experiments reveal a suppressive effect of Notch in osteoblast and osteoclast differentiation in development and in the postnatal bone, which establishes a role for Notch signaling in bone remodeling.

Science Signaling

6651873

10.1039/B912163N

Structure and dynamics of cross-linked actin networks

The actin cytoskeleton, a network of protein-polymers, is responsible for the mechanical stability of cells. This biopolymer network is also crucial for processes that require spatial and temporal variations in the network structure such as cell migration, division and intracellular transport. The cytoskeleton therefore has to combine structural integrity and mechanical stability with the possibility of fast and efficient network reorganization and restructuring. Cells meet this challenge by using proteins to link filamentous actin (F-actin) and construct complex networks. The molecular properties of the cross-linking proteins determine to a large extent the (micro)structure, viscoelastic properties and dynamics of the resulting networks. This review focuses on the structural polymorphism that can be induced by cross-linking proteins in reconstituted F-actin networks and summarizes recent results on how the molecular properties of cross-linking proteins dictate the ensuing viscoelastic properties.

Soft Matter

85077060

10.1016/S0928-4931(00)00166-1

Application of P450s for biosensing: combination of biotechnology and electrochemistry

Abstract P 450s are heme-containing proteins which catalyze monooxygenation and other reactions in oxidative metabolism of lipophilic compounds. They are promising enzymes for the application of biosensing probes. Biosensing of various compounds is possible when P 450s are immobilized on oxygen electrode or on ion-sensitive field effect transistor (ISFET). Competition assay with other substrate is another biosensing method based on the biochemical assay. Optical biosensor based on a resonance mirror was also reported. Genes in the upstream region of P 450 gene including the promoter is utilized to construct reporter gene system (RGS). The system responds to a trace amount of endocrine-disrupting substance to induce luciferase. Various biosensing methods with P 450s and P 450-related genes will be useful for medical application and ecological application in the near future.

Materials Science and Engineering: C

1173033

10.1088/0957-4484/18/29/295102

Molecular nanomechanics of nascent bone: fibrillar toughening by mineralization

Mineralized collagen fibrils are highly conserved nanostructural building blocks of bone. By a combination of molecular dynamics simulation and theoretical analysis it is shown that the characteristic nanostructure of mineralized collagen fibrils is vital for its high strength and its ability to sustain large deformation, as is relevant to the physiological role of bone, creating a strong and tough material. An analysis of the molecular mechanisms of protein and mineral phases under large deformation of mineralized collagen fibrils reveals a fibrillar toughening mechanism that leads to a manifold increase of energy dissipation compared to fibrils without mineral phase. This fibrillar toughening mechanism increases the resistance to fracture by forming large local yield regions around crack-like defects, a mechanism that protects the integrity of the entire structure by allowing for localized failure. As a consequence, mineralized collagen fibrils are able to tolerate microcracks of the order of several hundred micrometres in size without causing any macroscopic failure of the tissue, which may be essential to enable bone remodelling. The analysis proves that adding nanoscopic small platelets to collagen fibrils increases their Young's modulus and yield strength as well as their fracture strength. We find that mineralized collagen fibrils have a Young's modulus of 6.23 GPa (versus 4.59 GPa for the collagen fibril), yield at a tensile strain of 6.7% (versus 5% for the collagen fibril) and feature a fracture stress of 0.6 GPa (versus 0.3 GPa for the collagen fibril).

Nanotechnology

81740083

10.1007/978-1-4757-9724-4_3

Mechanical Design in Sea Anemones

By applying principles of fluid and solid mechanics to biological structures, I have studied the morphological adaptations of two species of sea anemones to the mechanical activities they perform and the environmental forces they encounter. The two species of anemones I used represent different extremes in mechanical behavior: Metridium senile, a calm-water species noted for the great range of shapes and sizes it can assume (Batham and Pantin, 1950), and Anthopleura xanthogrammica, a species occurring in areas exposed to extreme wave action (Hand, 1956; Dayton, 1971). I chose anemones because they are simple in structure, thus differences in morphology and function between species are easier to recognize and characterize than they would be for more complex animals.

Coelenterate Ecology and Behavior; The Journal of Experimental Biology

9431377

10.1016/S0945-053X(98)90059-2

Prolyl hydroxylase activity in tissue homogenates of annelids from deep sea hydrothermal vents.

Tissue homogenates of the deep sea annelids Alvinella caudata and Alvinella pompejana were found to contain enzyme activity resembling vertebrate prolyl 4-hydroxylase. The release of 3H2O from [3,4-(3)H]proline labeled, under-hydroxylated chicken protocollagen type I depended on the presence of the cofactors 2-oxoglutarate, ascorbate, Fe2+ and O2. The release of 3H2O could be inhibited by the prolyl 4-hydroxylase inhibitors zinc, 2,2'-dipyridyl, 3,4-dihydroxybenzoic acid and pyridine-2,4-dicarboxylate, as well as by the synthetic peptide (Pro-Pro-Gly)10. This synthetic peptide could also serve as substrate, because it enhanced the decarboxylation of 2-oxo[5-(14)C]glutarate. Alvinella prolyl hydroxylase appeared to be related to type II vertebrate enzyme because of its lack of affinity for poly (L-proline) and resistance to inactivation by an irreversible peptide inhibitor of chicken prolyl 4-hydroxylase. Maximal enzyme activity was observed in solutions with less than 10% oxygen saturation. By contrast, chicken enzyme was most active at saturating oxygen concentrations. Further data suggest that the Alvinella enzymes are able to accept the 2-oxo acids pyruvate, oxaloacetate and 2-oxoadipinate as substitutes of the cosubstarate 2-oxoglutarate. The data explain the high hydroxylation of Alvinella collagens despite the low oxygen concentrations around hydrothermal vents.

Matrix Biology

2540950

10.1098/RSBL.2009.0986

Diet effects on honeybee immunocompetence

The maintenance of the immune system can be costly, and a lack of dietary protein can increase the susceptibility of organisms to disease. However, few studies have investigated the relationship between protein nutrition and immunity in insects. Here, we tested in honeybees (Apis mellifera) whether dietary protein quantity (monofloral pollen) and diet diversity (polyfloral pollen) can shape baseline immunocompetence (IC) by measuring parameters of individual immunity (haemocyte concentration, fat body content and phenoloxidase activity) and glucose oxidase (GOX) activity, which enables bees to sterilize colony and brood food, as a parameter of social immunity. Protein feeding modified both individual and social IC but increases in dietary protein quantity did not enhance IC. However, diet diversity increased IC levels. In particular, polyfloral diets induced higher GOX activity compared with monofloral diets, including protein-richer diets. These results suggest a link between protein nutrition and immunity in honeybees and underscore the critical role of resource availability on pollinator health.

Biology Letters

84511635

10.1016/S0022-5193(05)80632-0

On the strength, stiffness and stability of tubular plant stems and leaves

thin walled tubes of circular cross-section are efficient structural elements and thus, as would be expected, are not uncommon in plants, especially those which belong to the Monocotyledonae. Traditional analyses of the strength of these tubular members utilize formulae which were developed for isotropic materials. The present paper deals with the great influence of the high elastic anisotropy of the plant tissue on the mechanical behavior of such tubular stems and leaves in bending. It will be seen that under these circumstances the propensity of the tube to fail due to non-linear effects (deformation of the cross-section) is greatly increased.

Journal of Theoretical Biology

7431911

10.1086/648555

Pollination Efficiency and the Evolution of Specialized Deceptive Pollination Systems

The ultimate causes of evolution of highly specialized pollination systems are little understood. We investigated the relationship between specialization and pollination efficiency, defined as the proportion of pollinated flowers relative to those that experienced pollen removal, using orchids with different pollination strategies as a model system. Rewarding orchids showed the highest pollination efficiency. Sexually deceptive orchids had comparably high pollination efficiency, but food‐deceptive orchids had significantly lower efficiency. Values for pollinator sharing (a measure of the degree of generalization in pollination systems) showed the reverse pattern, in that groups with high pollination efficiency had low values of pollinator sharing. Low pollinator sharing may thus be the basis for efficient pollination. Population genetic data indicated that both food‐ and sexually deceptive species have higher degrees of among‐population gene flow than do rewarding orchids. Thus, the shift from food to sexual deception may be driven by selection for more efficient pollination, without compromising the high levels of gene flow that are characteristic of deceptive species.

The American Naturalist

2733420

10.1098/RSPB.2009.1706

Egg attachment of the asparagus beetle Crioceris asparagi to the crystalline waxy surface of Asparagus officinalis

Plant surfaces covered with crystalline epicuticular waxes are known to be anti-adhesive, hardly wettable and preventing insect attachment. But there are insects that are capable of gluing their eggs to these surfaces by means of proteinaceous secretions. In this study, we analysed the bonding region between the eggs of Crioceris asparagi and the plant surface of Asparagus officinalis using light and cryo-scanning electron microscopy. The wettability of the plant surface by egg secretion was compared with that by Aqua Millipore water, aqueous sugar solution and chicken egg white. Furthermore, the force required to remove C. asparagi eggs from the plant surface was measured, in order to evaluate the egg's bonding strength. Mean pull-off force was 14.7 mN, which is about 8650 times higher than the egg weight. Egg glue was observed spreading over the wax crystal arrays on the plant cladophyll and wetting them. Similar wetting behaviour on the A. officinalis surface was observed for chicken egg white. Our results support the hypothesis that the mechanism of insect egg adhesion on micro- and nanostructured hydrophobic plant surfaces is related to the proteinaceous nature of adhesive secretions of insect eggs. The secretion wets superhydrophobic surfaces and after solidifying builds up a composite, consisting of the solidified glue and wax crystals, at the interface between the egg and plant cuticle.

Proceedings of The Royal Society B: Biological Sciences

84821862

10.2307/2398919

STRUCTURAL, BEHAVIORAL, AND PHYSIOLOGICAL ADAPTATIONS OF BEES (APOIDEA) FOR COLLECTING POLLEN'

Bees, like their wasp relatives, forage for and transport food to a nest as provisions for their offspring. Unlike female Sphecoidea which transport arthropods one at a time as prey, bees transport pollen requiring specialized scopal (brush) or corbicular (fringed plate) structures to transport the dustlike material externally. Scopae often exhibit further modifications in density and amount of plumosity in relation to the size and ornamentation of the pollen grains they transport. Bees also differ from sphecid wasps by possessing branched body hairs that are relatively densely packed. These hairs, the electrostatic surface potential, and specialized hair groups for extraction of hidden pollen are important in the acquisition of pollen from flowers. Structures for grooming (brushes, combs, and scrapers) and grooming behavior patterns are modified to permit manipulation and packing of pollen in the specialized transport structures. The addition of nectar, so that pollen is packed moist, is a behavior that permits the carrying of pollen of a great variety of sizes and ornamentations in relatively simplified scopae or in corbiculae. The addition of oils to the diet of some bees has resulted in a modified type of scopal structure that has a wooly area basally and stiff guard hairs extending distally and that can transport a mixture of oil and pollen. Special hairs on the fore and mid basitarsi and teeth of hind tibial spurs are modified as oil scraper and manipulation structures. The use of corbiculae in Apidae to transport nesting materials and the hind tibiae in male orchid bees (Euglossini: Apidae) for transporting aromatic compounds involves behavior patterns similar to those for pollen transport in grooming, manipulating, and packing the materials. Other behavioral and physiological adaptations important in the location and acquisition of pollen by bees include individual constancy, oligolecty, seasonal synchrony, preimaginal conditioning, daily synchrony, buzz pollination, and other responses to specific modes of pollen presentation. Most of the behavioral patterns involve learning. They may be modified by extrinsic factors, and they may modify intrinsic structural and physiological characters.

Annals of the Missouri Botanical Garden

8450728

10.1007/S10164-010-0222-4

A sticky situation: solifugids (Arachnida, Solifugae) use adhesive organs on their pedipalps for prey capture

Solifugids (Arachnida, Solifugae) have unique evertable adhesive organs on the tips of their pedipalps, named ‘suctorial’ or ‘palpal’ organs. Previous studies have shown that these organs enable solifugids to climb smooth glass-like surfaces and have hypothesized that these structures facilitate prey capture. Here, we use high-speed videography to demonstrate that the suctorial organs of Eremochelis bilobatus are its primary means of capturing insect prey. We also present calculations of the adhesive pressure exerted by these suctorial organs during real prey capture events.

Journal of Ethology

11488945

10.1890/07-0133.1

Mutualism as reciprocal exploitation: African plant-ants defend foliar but not reproductive structures.

The foundation of many plant-ant mutualisms is ant protection of plants from herbivores in exchange for food and/or shelter. While the role of symbiotic ants in protecting plants from stem- and leaf-feeding herbivores has been intensively studied, the relationship between ant defense and measures of plant fitness has seldom been quantified. We studied ant aggression, damage by herbivores and seed predators, and fruit production among Acacia drepanolobium trees occupied by four different acacia-ant species in an East African savanna. Levels of ant aggression in response to experimental disturbance differed strongly among the four species. All four ant species recruited more strongly to new leaf growth on host plants following disturbance, while recruitment to developing fruits was on average an order of magnitude lower. Host plants occupied by more aggressive ant species suffered significantly less vegetative damage from leaf-feeding insects, stem-boring beetles, and vertebrate browsers than host plants occupied by less aggressive ant species. However, there were no differences among fruiting host plants occupied by different ant species in levels of seed predation by bruchid seed predators. Fruit production on host trees was significantly correlated with tree stem diameter but not with the identity of resident ants. Our results demonstrate that defense of host plants may differ substantially among ant species and between vegetative and reproductive structures and that fruit production is not necessarily correlated with high levels of aggression by resident ants.

Ecology

42047872

10.1016/J.ASD.2006.08.011

Evolution of color and vision of butterflies.

Butterfly eyes consist of three types of ommatidia, which are more or less randomly arranged in a spatially regular lattice. The corneal nipple array and the tapetum, optical structures that many but not all butterflies share with moths, suggest that moths are ancestral to butterflies, in agreement with molecular phylogeny. A basic set of ultraviolet-, blue- and green-sensitive receptors, encountered among nymphalid butterflies, forms the basis for trichromatic vision. Screening pigments surrounding the light-receiving rhabdoms can modify the spectral sensitivity of the photoreceptors so that the sensitivity peak is in the violet, yellow, red, or even deep-red, specifically in swallowtails (Papilionidae) and whites (Pieridae), thus enhancing color discriminability. The photoreceptor sensitivity spectra are presumably tuned to the wing colors of conspecific butterflies.

Arthropod Structure & Development

27251015

10.1126/SCIENCE.201.4356.614

Temperatures of Desert Plants: Another Perspective on the Adaptability of Leaf Size

Surface temperatures of perennial plants in the Sonoran Desert of California ranged from 20�C above air temperature to over 18�C below air temperature during rapid growth periods following rain. Desert cactus with large photosynthetic stem surfaces had the highest temperatures and lowest transpiration rates. Perennial plants with relatively small leaves had moderate transpiration rates and leaf temperatures close to air temperature. Desert perennials with relatively large leaves had leaf temperatures well below air temperature along with the greatest accompanying transpiration rates of over 20 micrograms per square centimeter per second, but also had correspondingly low temperatures for maximum photosynthesis. The low leaf temperatures measured for these large-leafed species are an exception to the more common pattern for desert plants whereby a smaller leaf size prevents overheating and leads to reductions in transpiration and increased water-use efficiency. The contribution of a larger leaf size to a lower leaf temperature, and thus higher rate of photosynthesis for these large-leafed species, may represent an adaptive pattern previously unrecognized for desert plants.

Science

3832452

10.1038/SREP00131

Hagfish predatory behaviour and slime defence mechanism

Hagfishes (Myxinidae), a family of jawless marine pre-vertebrates, hold a unique evolutionary position, sharing a joint ancestor with the entire vertebrate lineage. They are thought to fulfil primarily the ecological niche of scavengers in the deep ocean. However, we present new footage from baited video cameras that captured images of hagfishes actively preying on other fish. Video images also revealed that hagfishes are able to choke their would-be predators with gill-clogging slime. This is the first time that predatory behaviour has been witnessed in this family, and also demonstrates the instantaneous effectiveness of hagfish slime to deter fish predators. These observations suggest that the functional adaptations and ecological role of hagfishes, past and present, might be far more diverse than previously assumed. We propose that the enduring success of this oldest extant family of fishes over 300 million years could largely be due to their unique combination of functional traits.

Scientific Reports

26518342

10.1098/RSPB.2004.2702

Gait selection in the ostrich: mechanical and metabolic characteristics of walking and running with and without an aerial phase

It has been argued that minimization of metabolic–energy costs is a primary determinant of gait selection in terrestrial animals. This view is based predominantly on data from humans and horses, which have been shown to choose the most economical gait (walking, running, galloping) for any given speed. It is not certain whether a minimization of metabolic costs is associated with the selection of other prevalent forms of terrestrial gaits, such as grounded running (a widespread gait in birds). Using biomechanical and metabolic measurements of four ostriches moving on a treadmill over a range of speeds from 0.8 to 6.7 m s−1, we reveal here that the selection of walking or grounded running at intermediate speeds also favours a reduction in the metabolic cost of locomotion. This gait transition is characterized by a shift in locomotor kinetics from an inverted–pendulum gait to a bouncing gait that lacks an aerial phase. By contrast, when the ostrich adopts an aerial–running gait at faster speeds, there are no abrupt transitions in mechanical parameters or in the metabolic cost of locomotion. These data suggest a continuum between grounded and aerial running, indicating that they belong to the same locomotor paradigm.

Proceedings of The Royal Society B: Biological Sciences

7031019

10.1371/JOURNAL.PONE.0000457

Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi

Background Melanin pigments are ubiquitous in nature. Melanized microorganisms are often the dominating species in certain extreme environments, such as soils contaminated with radionuclides, suggesting that the presence of melanin is beneficial in their life cycle. We hypothesized that ionizing radiation could change the electronic properties of melanin and might enhance the growth of melanized microorganisms. Methodology/Principal Findings Ionizing irradiation changed the electron spin resonance (ESR) signal of melanin, consistent with changes in electronic structure. Irradiated melanin manifested a 4-fold increase in its capacity to reduce NADH relative to non-irradiated melanin. HPLC analysis of melanin from fungi grown on different substrates revealed chemical complexity, dependence of melanin composition on the growth substrate and possible influence of melanin composition on its interaction with ionizing radiation. XTT/MTT assays showed increased metabolic activity of melanized C. neoformans cells relative to non-melanized cells, and exposure to ionizing radiation enhanced the electron-transfer properties of melanin in melanized cells. Melanized Wangiella dermatitidis and Cryptococcus neoformans cells exposed to ionizing radiation approximately 500 times higher than background grew significantly faster as indicated by higher CFUs, more dry weight biomass and 3-fold greater incorporation of 14C-acetate than non-irradiated melanized cells or irradiated albino mutants. In addition, radiation enhanced the growth of melanized Cladosporium sphaerospermum cells under limited nutrients conditions. Conclusions/Significance Exposure of melanin to ionizing radiation, and possibly other forms of electromagnetic radiation, changes its electronic properties. Melanized fungal cells manifested increased growth relative to non-melanized cells after exposure to ionizing radiation, raising intriguing questions about a potential role for melanin in energy capture and utilization.

PLOS ONE

40724077

10.1016/J.MICROMESO.2011.12.005

Enzymatic conversion of CO(2) to bicarbonate in functionalized mesoporous silica.

We report here a concept converting carbon dioxide to biocarbonate in a biomimetic nanoconfiguration. Carbonic anhydrase (CA), the fastest enzyme that can covert carbon dioxide to bicarbonate, can be spontaneously entrapped in carboxylic acid group-functionalized mesoporous silica (HOOC-FMS) with super-high loading density (up to 0.5 mg of protein/mg of FMS) in sharp contrast to normal porous silica. The binding of CA to HOOC-FMS resulted in a partial conformational change comparing to the enzyme free in solution, but it can be overcome with increased protein loading density. The higher the protein loading density, the less conformational change, hence the higher enzymatic activity and the higher enzyme immobilization efficiency (up to >60%). The released enzyme still displayed the native conformational structure and the same high enzymatic activity as that prior to the enzyme entrapment, indicating that the conformational change resulted from the electrostatic interaction of CA with HOOC-FMS was not permanent. This work may provide a new approach converting carbon dioxide to biocarbonate that can be integrated with the other part of biosynthesis process for the assimilation of carbon dioxide.

Microporous and Mesoporous Materials

129731225

10.1002/(SICI)1096-9837(199804)23:4<291::AID-ESP844>3.0.CO;2-A

The role of biota in the initiation and growth of islands on the floodplain of the Okavango alluvial fan, Botswana

A group of islands of varying size on the floodplain of the Okavango alluvial fan, were studied to establish the processes which lead to the initiation and growth of islands. It was found that islands are initiated by the mound-building activities of the termite Macrotermes michaelseni. These termites import fine grained materials to use as a mortar for the construction of epigeal mounds. Their activities create a topographic feature, raised above the level of seasonal flooding, and also change the physical properties and nutrient status of the mound soil. Shrubs and trees are able to colonize these mounds, which results in increased transpiration. As a result, precipitation of calcite and silica from the shallow ground water occurs preferentially beneath the mounds, resulting in vertical and especially lateral growth, causing island expansion. © 1998 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms

35178716

10.2108/ZSJ.26.632

Functional Changes with Feeding in the Gastro-Intestinal Epithelia of the Burmese Python (Python molurus)

The morphology of the digestive system in fasting and refed Burmese pythons was determined, as well as the localization of the proton (H+, K+-ATPase) and sodium (Na+, K+-ATPase) pumps. In fasting pythons, oxyntopeptic cells located within the fundic glands are typically non-active, with a thick apical tubulovesicular system and numerous zymogen granules. They become active immediately after feeding but return to a non-active state 3 days after the ingestion of the prey. The proton pump, expressed throughout the different fasting/feeding states, is either sequestered in the tubulovesicular system in non-active cells or located along the apical digitations extending within the crypt lumen in active cells. The sodium pump is rapidly upregulated in fed animals and is classically located along the baso-lateral membranes of the gastric oxyntopeptic cells. In the intestine, it is only expressed along the lateral membranes of the enterocytes, i.e., above the lateral spaces and not along the basal side of the cells. Thus, solute transport within the intestinal lining is mainly achieved through the apical part of the cells and across the lateral spaces while absorbed fat massively crosses the entire height of the cells and flows into the intercellular spaces. Therefore, in the Burmese python, the gastrointestinal cellular system quickly upregulates after feeding, due to inexpensive cellular changes, passive mechanisms, and the progressive activation and synthesis of key enzymes such as the sodium pump. This cell plasticity also allows anticipation of the next fasting and feeding periods.

Zoological Science

55194467

10.1088/0960-1317/15/7/011

Biomimetic strain-sensing microstructure for improved strain sensor: fabrication results and optical characterization

This paper describes the fabrication, and early optical characterization results of a new biomimetic strain-sensing microstructure. The microstructures were inspired from the campaniform sensillum, a highly sensitive strain sensor found in the exocuticle layer of insects. We investigate the natural strain-sensor characteristics by mimicking some of its simplest structural features. Blind-hole- and membrane-structural features were combined and fabricated as membrane-in-recess microstructure. To investigate the strain-sensing (or strain-amplifying) property of the microstructure, an optical characterization setup was devised based on the interference pattern formed by reflected laser beams from different surfaces of the microstructures. Preliminary qualitative analysis of the results obtained shows unsimilar intensity level changes as a function of spatial location on the membrane, thus indicated the biomimetic microstructure's strain-amplifying property. This property could be utilized for future improvement of currently available planar-based conventional strain sensors.

Journal of Micromechanics and Microengineering

98164146

10.1007/S10404-007-0163-6

Optimal design of microfluidic networks using biologically inspired principles

From the earliest of times, Man has sought to replicate ideas that have evolved naturally in plants and animals. Understanding and extracting these “natural” design strategies has opened up a whole new field of research known as biomimetics. Designs formulated using biologically inspired principles range from novel surface treatments that mimic physiological processes to geometrical optimization for improving the performance of a system. In this paper, we will show how biomimetic principles based on the laws that govern biological vascular trees can be used to design artificial microfluidic distribution systems. The study focuses specifically on microfluidic manifolds composed of constant-depth rectangular- or trapezoidal-sectioned channels, as these geometries can readily be fabricated using standard micro-fabrication techniques. We will show that it is possible to introduce a prescribed element of flow control into the system by carefully selecting the branching parameter that governs the change in channel dimension at each bifurcation.

Microfluidics and Nanofluidics

8926689

10.1126/SCIENCE.1173793

An Acidic Matrix Protein, Pif, Is a Key Macromolecule for Nacre Formation

Making Mother of Pearl Nacre is an iridescent layer of calcium carbonate lining the inside of shells of marine mollusks and is commonly known as “mother of pearl.” It is composed of layers of uniformly oriented crystals of aragonite (a metastable form of calcium carbonate) separated by layers of organic matrix. How the ordered structure of aragonite layers is achieved has been unclear. Suzuki et al. (p. 1388, published online 13 August 2009; see the Perspective by Kröger) identified two acidic matrix proteins (Pif 97 and Pif 80) that regulate nacre formation in the Japanese pearl oyster. The proteins appear to form a complex in which Pif 80 binds to aragonite and Pif 97 binds to other macromolecules in the organic matrix. A matrix protein is identified that regulates nacre formation in the Japanese pearl oyster. The mollusk shell is a hard tissue consisting of calcium carbonate crystals and an organic matrix. The nacre of the shell is characterized by a stacked compartment structure with a uniformly oriented c axis of aragonite crystals in each compartment. Using a calcium carbonate–binding assay, we identified an acidic matrix protein, Pif, in the pearl oyster Pinctada fucata that specifically binds to aragonite crystals. The Pif complementary DNA (cDNA) encoded a precursor protein, which was posttranslationally cleaved to produce Pif 97 and Pif 80. The results from immunolocalization, a knockdown experiment that used RNA interference, and in vitro calcium carbonate crystallization studies strongly indicate that Pif regulates nacre formation.

Science

5224052

10.1016/J.JMBBM.2012.09.004

The weak interfaces within tough natural composites: experiments on three types of nacre.

Mineralization is a typical strategy used in natural materials to achieve high stiffness and hardness for structural functions such as skeletal support, protection or predation. High mineral content generally leads to brittleness, yet natural materials such as bone, mollusk shells or glass sponge achieve relatively high toughness considering the weakness of their constituents through intricate microstructures. In particular, nanometers thick organic interfaces organized in micro-architectures play a key role in providing toughness by various processes including crack deflection, crack bridging or energy dissipation. While these interfaces are critical in these materials, their composition, structure and mechanics is often poorly understood. In this work we focus on nacre, one of the most impressive hard biological materials in terms of toughness. We performed interfacial fracture tests on chevron notched nacre samples from three different species: red abalone, top shell and pearl oyster. We found that the intrinsic toughness of the interfaces is indeed found to be extremely low, in the order of the toughness of the mineral inclusions themselves. Such low toughness is required for the cracks to follow the interfaces, and to deflect and circumvent the mineral tablets. This result highlights the efficacy of toughening mechanisms in natural materials, turning low-toughness inclusions and interfaces into high-performance composites. We found that top shell nacre displayed the highest interfacial toughness, because of higher surface roughness and a more resilient organic material, and also through extrinsic toughening mechanisms including crack deflection, crack bridging and process zone. In the context of biomimetics, the main implication of this finding is that the interface in nacre-like composite does not need to be tough; the extensibility or ductility of the interfaces may be more important than their strength and toughness to produce toughness at the macroscale.

Journal of The Mechanical Behavior of Biomedical Materials

206638368

10.1126/SCIENCE.AAB3564

Keeping cool: Enhanced optical reflection and radiative heat dissipation in Saharan silver ants

Keeping cool Silver ants inhabit one of the hottest and driest environments on Earth, the Saharan sands, where most insects shrivel and die moments after contact. Shi et al. show that the triangular shape of the silver hairs that cover their bodies enables this existence. The hairs both increase the reflection of near-infrared rays and dissipate heat from the ants' bodies, even under full sun conditions. Evolution's simple solution to intense heat management in this species could lead to better designs for passive cooling of human-produced objects. Science, this issue p. 298 Silver hairs on Saharan ants facilitate both reflection and dissipation of intense heat. Saharan silver ants, Cataglyphis bombycina, forage under extreme temperature conditions in the African desert. We show that the ants’ conspicuous silvery appearance is created by a dense array of triangular hairs with two thermoregulatory effects. They enhance not only the reflectivity of the ant’s body surface in the visible and near-infrared range of the spectrum, where solar radiation culminates, but also the emissivity of the ant in the mid-infrared. The latter effect enables the animals to efficiently dissipate heat back to the surroundings via blackbody radiation under full daylight conditions. This biological solution for a thermoregulatory problem may lead to the development of biomimetic coatings for passive radiative cooling of objects.

Science

83725612

10.1016/S0022-5193(87)80001-2

Flight of a samara, Alsomitra macrocarpa

The steady gliding flight of samples of Alsomitra macrocarpa samara was filmed and analysed. By using the observed data, the flight performance of the samara was made clear. The lift-to-drag ratio or the gliding ratio was about 3 ∼ 4 and the rate of descent was 0·3 ∼ 0·7 m/sec, which was smaller than those of other rotary seeds. The flight was so stable that samples were seen to take their optimal trimmed angle of attack with a value between the maximum gliding ratio and the minimum rate of descent. The aerodynamic function of the husk for the distribution of the seeds was also revealed by making wind tunnel tests of the husk.

Journal of Theoretical Biology