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183
84427195
10.1080/11263500600756546
84,427,195
Plant and lichen colonization in an asbestos mine: Spontaneous bioattenuation limits air dispersion of fibres
Abstract Plant and lichen phytosociological studies describe the different dynamic stages of colonization. This approach has been applied to the Balangero asbestos mine, the most important of Western Europe up to 1990, which is a potential source for the air-dispersion of carcinogenic fibres. Vegetation relevés and maps have shown that plants and lichens develop spontaneously on the asbestos-rich substrates. Early colonization stages with low-covering hyperaccumulators, such as Thlaspi sylvium and Minuartia laricifolia, and with Thymus alpestris and T. cfr. humifusus, are followed, some decades later, by mature plant communities, which completely cover the asbestos-rich debris, thereby limiting the dispersion of fibres. Lichen colonization, even when limited to low covering early stages with pioneer crustose species, such as Scoliciosporum umbrinum and Candelariella vitellina, and young foliose thalli of Xanthoparmelia tinctina, is important whenever asbestos veins are exposed on serpentinite blocks and walls. Plants and lichens can be considered as bioattenuation (spontaneous bioremediation) agents in ecological recovery.
1
Plant Biosystems
10081925
10.1088/1748-3182/6/4/046001
10,081,925
The characterization, replication and testing of dermal denticles of Scyliorhinus canicula for physical mechanisms of biofouling prevention.
There is a current need to develop novel non-toxic antifouling materials. The mechanisms utilized by marine organisms to prevent fouling of external surfaces are of interest in this regard. Biomimicry of these mechanisms and the ability to transfer the antifouling characteristics of these surfaces to artificial surfaces are a highly attractive prospect to those developing antifouling technologies. In order to achieve this, the mechanisms responsible for any antifouling ability must be elucidated from the study of the natural organism and the critical surface parameters responsible for fouling reduction. Dermal denticles of members of the shark family have been speculated to possess some natural, as yet unidentified antifouling mechanism related to the physical presence of denticles. In this study, the dermal denticles of one particular member of the slow-swimming sharks, Scyliorhinus canicula were characterized and it was found that a significant natural variation in denticle dimensions exists in this species. The degree of denticle surface contamination was quantified on denticles at various locations and it was determined that the degree of contamination of the dorsal surface of denticles varies with the position on the shark body. In addition, we successfully produced synthetic sharkskin samples using the real skin as a template. Testing of the produced synthetic skin in field conditions resulted in significant differences in material attachment on surfaces exhibiting denticles of different dimensions.
1
Bioinspiration & Biomimetics
8607613
10.1007/BF02135966
8,607,613
Responses of single neurons in the olfactory bulbs of rabbits, dogs, and cats to X-rays
Die durch Röntgenstrahlen (1 R/sec) erzeugten elektrischen Impulse einzelner Nervenzellen der Geruchszwiebel wurden in narkotisierten Katzen, Kaninchen und Hunden gemessen. Als typische Reaktion wurde eine kurzfristige Erhöhung der elektrischen Impulse gefunden. Somit sind die von Röntgenstrahlen ausgelösten elektrischen Impulse des Geruchsystems kein artspezifisches, sondern vielmehr ein allgemeines Phänomen.
1
Cellular and Molecular Life Sciences
35057861
10.1126/SCIENCE.1120182
35,057,861
Fuel-Powered Artificial Muscles
Artificial muscles and electric motors found in autonomous robots and prosthetic limbs are typically battery-powered, which severely restricts the duration of their performance and can necessitate long inactivity during battery recharge. To help solve these problems, we demonstrated two types of artificial muscles that convert the chemical energy of high–energy-density fuels to mechanical energy. The first type stores electrical charge and uses changes in stored charge for mechanical actuation. In contrast with electrically powered electrochemical muscles, only half of the actuator cycle is electrochemical. The second type of fuel-powered muscle provides a demonstrated actuator stroke and power density comparable to those of natural skeletal muscle and generated stresses that are over a hundred times higher.
1
Science
206997317
10.1016/J.MOLCEL.2017.02.018
206,997,317
Tardigrades Use Intrinsically Disordered Proteins to Survive Desiccation.
Tardigrades are microscopic animals that survive a remarkable array of stresses, including desiccation. How tardigrades survive desiccation has remained a mystery for more than 250 years. Trehalose, a disaccharide essential for several organisms to survive drying, is detected at low levels or not at all in some tardigrade species, indicating that tardigrades possess potentially novel mechanisms for surviving desiccation. Here we show that tardigrade-specific intrinsically disordered proteins (TDPs) are essential for desiccation tolerance. TDP genes are constitutively expressed at high levels or induced during desiccation in multiple tardigrade species. TDPs are required for tardigrade desiccation tolerance, and these genes are sufficient to increase desiccation tolerance when expressed in heterologous systems. TDPs form non-crystalline amorphous solids (vitrify) upon desiccation, and this vitrified state mirrors their protective capabilities. Our study identifies TDPs as functional mediators of tardigrade desiccation tolerance, expanding our knowledge of the roles and diversity of disordered proteins involved in stress tolerance.
1
Molecular Cell
85099062
10.2307/1939003
85,099,062
BIRD ACTIVITY AND SEED DISPERSAL OF A TROPICAL WET FOREST TREE
Feeding assemblages of birds were observed throughout a fruiting season at a Costa Rican population of the rain forest tree Casearia corymbosa in order to distinguish effective dispersal agents from visitors which used arils for food without dispersing seeds. This system is of special interest because the tree fruits during an annual period of fruit scarcity in a forest characterized by high proportions of animal-dispersed plants and obligate frugivores. Results show that the Masked Tityra (Tityra semifasciata) is an effective dispersal agent of seeds of this tree because it: (1) regurgitates viable seeds, (2) is a common and regular visitor throughout the season, (3) has high feeding rates, (4) removes seeds from the vicinity of the parent tree before processing them, and (5) depends on this rather than other plants fruiting at the same time. Twenty-one other visitors were deficient dispersers, although some depended heavily on fruit of this tree for food. Two parrots (Amazona autumnalis and Amazona farinosa) preclude dispersal by strip- ping arils with their bills and dropping all seeds in situ. Fourteen species are occasional visitors. Five visitors (Ramphastos sulfuratus, Ramphastos swainsonii, Pteroglossus torquatus, Myiozetetes similis, and Myiozetetes granadensis) process seeds undamaged and are sometimes numerically abun- dant, but are absent part of the season and tend to regurgitate seeds in situ. Because fruiting activity of this tree occurs during annual scarcity, it represents a pivotal species in the community. Three obligate frugivores, including one effective disperser and two fruit thieves, depend almost entirely on it for food for periods of 2-6 wk. I hypothesize that extinction of this plant at this site would lead to disappearance of these birds, and would almost certainly depress recruitment of other species of trees for which they serve as dispersal agents at other times of the year.
1
Ecology
39692180
10.1073/PNAS.1109355108
39,692,180
Inferring the rules of interaction of shoaling fish
Collective motion, where large numbers of individuals move synchronously together, is achieved when individuals adopt interaction rules that determine how they respond to their neighbors’ movements and positions. These rules determine how group-living animals move, make decisions, and transmit information between individuals. Nonetheless, few studies have explicitly determined these interaction rules in moving groups, and very little is known about the interaction rules of fish. Here, we identify three key rules for the social interactions of mosquitofish (Gambusia holbrooki): (i) Attraction forces are important in maintaining group cohesion, while we find only weak evidence that fish align with their neighbor’s orientation; (ii) repulsion is mediated principally by changes in speed; (iii) although the positions and directions of all shoal members are highly correlated, individuals only respond to their single nearest neighbor. The last two of these rules are different from the classical models of collective animal motion, raising new questions about how fish and other animals self-organize on the move.
1
Proceedings of the National Academy of Sciences of the United States of America
41761750
10.2307/2656954
41,761,750
A new pollination system: dung-beetle pollination discovered in Orchidantha inouei (Lowiaceae, Zingiberales) in Sarawak, Malaysia.
Lowiaceae, a family of the Zingiberales, comprise 11 species in the single genus Orchidantha. Here we present the first report on the pollination of Lowiaceae and describe a new system of dung-beetle pollination from Sarawak, Borneo. Orchidantha inouei has a zygomorphic flower located just above the ground. Observations revealed that the plant is visited frequently and is pollinated by scarabaeid dung beetles, mainly members of the genus Onthophagus. All four species of Onthophagus collected on O. inouei have also been caught using traps baited with dung or carrion in Borneo. Onthophagus was presumably attracted to the dung-like odor of the flower. Pollination of O. inouei is different from other examples of beetle pollination in that its flower provides neither reward nor protected space. Dung beetles are excellent at following a particular dung scent. Orchidantha is the only genus that includes species lacking floral nectar. It is interesting that this deception pollination using dung beetles was found in Zingiberales, in which all known species have mutual and specialized relationships with their long-distance, but costly, pollinators-bees, birds, and bats.
1
American Journal of Botany
12186698
10.1039/B703021P
12,186,698
Expanding dialogues: from natural autoinducers to non-natural analogues that modulate quorum sensing in Gram-negative bacteria.
Bacteria are capable of "communicating" their local population densities via a process termed quorum sensing (QS). Gram-negative bacteria use N-acylated l-homoserine lactones (AHLs), in conjunction with their cognate LuxR-type receptors, as their primary signalling circuit for QS. In this critical review, we examine AHL signalling in Gram-negative bacteria with a primary focus on the design of non-natural AHLs, their structure-activity relationships, and their application in chemical biological approaches to study QS (72 references).
1
Chemical Society Reviews
4348391
10.1038/NATURE00823
4,348,391
Local dispersal promotes biodiversity in a real-life game of rock–paper–scissors
One of the central aims of ecology is to identify mechanisms that maintain biodiversity. Numerous theoretical models have shown that competing species can coexist if ecological processes such as dispersal, movement, and interaction occur over small spatial scales. In particular, this may be the case for non-transitive communities, that is, those without strict competitive hierarchies. The classic non-transitive system involves a community of three competing species satisfying a relationship similar to the children's game rock–paper–scissors, where rock crushes scissors, scissors cuts paper, and paper covers rock. Such relationships have been demonstrated in several natural systems. Some models predict that local interaction and dispersal are sufficient to ensure coexistence of all three species in such a community, whereas diversity is lost when ecological processes occur over larger scales. Here, we test these predictions empirically using a non-transitive model community containing three populations of Escherichia coli. We find that diversity is rapidly lost in our experimental community when dispersal and interaction occur over relatively large spatial scales, whereas all populations coexist when ecological processes are localized.
1
Nature
39079534
10.1111/J.1365-2435.2009.01632.X
39,079,534
Floral volatiles controlling ant behaviour
P>1. Ants show complex interactions with plants, both facultative and mutualistic, ranging from grazers through seed predators and dispersers to herders of some herbivores and guards against others. But ants are rarely pollinators, and their visits to flowers may be detrimental to plant fitness. 2. Plants therefore have various strategies to control ant distributions, and restrict them to foliage rather than flowers. These 'filters' may involve physical barriers on or around flowers, or 'decoys and bribes' sited on the foliage (usually extrafloral nectaries - EFNs). Alternatively, volatile organic compounds (VOCs) are used as signals to control ant behaviour, attracting ants to leaves and/or deterring them from functional flowers. Some of the past evidence that flowers repel ants by VOCs has been equivocal and we describe the shortcomings of some experimental approaches, which involve behavioural tests in artificial conditions. 3. We review our previous study of myrmecophytic acacias, which used in situ experiments to show that volatiles derived from pollen can specifically and transiently deter ants during dehiscence, the effects being stronger in ant-guarded species and more effective on resident ants, both in African and Neotropical species. In these plants, repellence involves at least some volatiles that are known components of ant alarm pheromones, but are not repellent to beneficial bee visitors. 4. We also present new evidence of ant repellence by VOCs in temperate flowers, which is usually pollen-based and active on common European ants. We use these data to indicate that across a wide range of plants there is an apparent trade-off in ant-controlling filter strategies between the use of defensive floral volatiles and the alternatives of decoying EFNs or physical barriers.
1
Functional Ecology
253103
10.1098/RSIF.2009.0556
253,103
Scaling and mechanics of carnivoran footpads reveal the principles of footpad design
In most mammals, footpads are what first strike ground with each stride. Their mechanical properties therefore inevitably affect functioning of the legs; yet interspecific studies of the scaling of locomotor mechanics have all but neglected the feet and their soft tissues. Here we determine how contact area and stiffness of footpads in digitigrade carnivorans scale with body mass in order to show how footpads’ mechanical properties and size covary to maintain their functional integrity. As body mass increases across several orders of magnitude, we find the following: (i) foot contact area does not keep pace with increasing body mass; therefore pressure increases, placing footpad tissue of larger animals potentially at greater risk of damage; (ii) but stiffness of the pads also increases, so the tissues of larger animals must experience less strain; and (iii) total energy stored in hindpads increases slightly more than that in the forepads, allowing additional elastic energy to be returned for greater propulsive efficiency. Moreover, pad stiffness appears to be tuned across the size range to maintain loading regimes in the limbs that are favourable for long-bone remodelling. Thus, the structural properties of footpads, unlike other biological support-structures, scale interspecifically through changes in both geometry and material properties, rather than geometric proportions alone, and do so with consequences for both maintenance and operation of other components of the locomotor system.
1
Journal of the Royal Society Interface
215780969
10.1371/JOURNAL.PBIO.1000139
215,780,969
RIN4 Functions with Plasma Membrane H+-ATPases to Regulate Stomatal Apertures during Pathogen Attack
In plants, the protein Rin4 acts with the plasma membrane H+-ATPase to regulate pathogen entry and the innate immune response, in part, through the regulation of stomatal closure.
1
PLOS Biology
221870716
10.1002/JMOR.20083
221,870,716
Scale morphology and flexibility in the shortfin mako Isurus oxyrinchus and the blacktip shark Carcharhinus limbatus
Cover illustration. The shortfin mako Isurus oxyrinchus is perhaps the fastest swimming shark. The modified scales on the lateral flank of the shark are highly flexible and are believed to erect during rapid swimming. Erection of the flank scales and resulting drag reduction is hypothesized to be passively driven by localized flow patterns over the skin. The cover image, “Mako Moon”, is courtesy of Don Ray of donrayart.com. See Motta et al., pp. 1096–1110 in this issue of the Journal of Morphology.
1
Physics of Fluids; Philosophical Transactions of the Royal Society A; Bioinspiration & Biomimetics; Journal of Morphology; The Journal of Experimental Biology; Journal of Fish Biology
3950718
10.1073/PNAS.1011033108
3,950,718
Bacterial biofilm shows persistent resistance to liquid wetting and gas penetration
Most of the world’s bacteria exist in robust, sessile communities known as biofilms, ubiquitously adherent to environmental surfaces from ocean floors to human teeth and notoriously resistant to antimicrobial agents. We report the surprising observation that Bacillus subtilis biofilm colonies and pellicles are extremely nonwetting, greatly surpassing the repellency of Teflon toward water and lower surface tension liquids. The biofilm surface remains nonwetting against up to 80% ethanol as well as other organic solvents and commercial biocides across a large and clinically important concentration range. We show that this property limits the penetration of antimicrobial liquids into the biofilm, severely compromising their efficacy. To highlight the mechanisms of this phenomenon, we performed experiments with mutant biofilms lacking ECM components and with functionalized polymeric replicas of biofilm microstructure. We show that the nonwetting properties are a synergistic result of ECM composition, multiscale roughness, reentrant topography, and possibly yet other factors related to the dynamic nature of the biofilm surface. Finally, we report the impenetrability of the biofilm surface by gases, implying defense capability against vapor-phase antimicrobials as well. These remarkable properties of B. subtilis biofilm, which may have evolved as a protection mechanism against native environmental threats, provide a new direction in both antimicrobial research and bioinspired liquid-repellent surface paradigms.
1
Proceedings of the National Academy of Sciences of the United States of America
29462651
10.1242/JEB.050567
29,462,651
The mechanics of explosive dispersal and self-burial in the seeds of the filaree, Erodium cicutarium (Geraniaceae)
SUMMARY The filaree (Erodium cicutarium), a small, flowering plant related to geraniums, possesses a unique seed dispersal mechanism: the plant can fling its seeds up to half a meter away; and the seeds can bury themselves by drilling into the ground, twisting and untwisting in response to changes in humidity. These feats are accomplished using awns, helical bristles of dead but hygroscopically active tissue attached to the seeds. Here, we describe the kinematics of explosive dispersal and self-burial based on detailed high-speed and time-lapse videos. We use these observations to develop a simple mechanical model that accounts for the coiling behavior of the awn and allows comparison of the strain energy stored in the awn with the kinetic energy at launch. The model is used to examine tradeoffs between dispersal distance and reliability of the dispersal mechanism. The mechanical model may help in understanding the invasive potential of this species and provides a framework for examining other evolutionary tradeoffs in seed dispersal mechanisms among the Geraniaceae.
1
The Journal of Experimental Biology
7997880
10.1073/PNAS.0504307102
7,997,880
NO-mediated cytoprotection: instant adaptation to oxidative stress in bacteria.
Numerous sophisticated systems have been described that protect bacteria from increased levels of reactive oxygen species. Although indispensable during prolonged oxidative stress, these response systems depend on newly synthesized proteins, and are hence both time and energy consuming. Here, we describe an "express" cytoprotective system in Bacillus subtilis which depends on nitric oxide (NO). We show that NO immediately protects bacterial cells from reactive oxygen species by two independent mechanisms. NO transiently suppresses the enzymatic reduction of free cysteine that fuels the damaging Fenton reaction. In addition, NO directly reactivates catalase, a major antioxidant enzyme that has been inhibited in vivo by endogenous cysteine. Our data also reveal a critical role for bacterial NO-synthase in adaptation to oxidative stress associated with fast metabolic changes, and suggest a possible role for NO in defending pathogens against immune oxidative attack.
1
Proceedings of the National Academy of Sciences of the United States of America
6082701
10.1242/JEB.035618
6,082,701
Slippery surfaces of pitcher plants: Nepenthes wax crystals minimize insect attachment via microscopic surface roughness
SUMMARY Pitcher plants of the genus Nepenthes efficiently trap and retain insect prey in highly specialized leaves. Besides a slippery peristome which inhibits adhesion of insects they employ epicuticular wax crystals on the inner walls of the conductive zone of the pitchers to hamper insect attachment by adhesive devices. It has been proposed that the detachment of individual crystals and the resulting contamination of adhesive organs is responsible for capturing insects. However, our results provide evidence in favour of a different mechanism, mainly based on the stability and the roughness of the waxy surface. First, we were unable to detect a large quantity of crystal fragments on the pads of insects detached from mature pitcher surfaces of Nepenthes alata. Second, investigation of the pitcher surface by focused ion beam treatment showed that the wax crystals form a compact 3D structure. Third, atomic force microscopy of the platelet-shaped crystals revealed that the crystals are mechanically stable, rendering crystal detachment by insect pads unlikely. Fourth, the surface profile parameters of the wax layer showed striking similarities to those of polishing paper with low grain size. By measuring friction forces of insects on this artificial surface we demonstrate that microscopic roughness alone is sufficient to minimize insect attachment. A theoretical model shows that surface roughness within a certain length scale will prevent adhesion by being too rough for adhesive pads but not rough enough for claws.
1
The Journal of Experimental Biology
33883558
10.1016/S1047-8477(03)00142-4
33,883,558
Young's modulus varies with differential orientation of keratin in feathers.
Feathers are composed of a structure that, whilst being very light, is able to withstand the large aerodynamic forces exerted upon them during flight. To explore the contribution of molecular orientation to feather keratin mechanical properties, we have examined the nanoscopic organisation of the keratin molecules by X-ray diffraction techniques and have confirmed a link between this and the Young's modulus of the feather rachis. Our results indicate that along the rachis length, from calamus to tip, the keratin molecules become more aligned than at the calamus before returning to a state of higher mis-orientation towards the tip of the rachis. We have also confirmed the general trend of increasing Young's modulus with distance along the rachis. Furthermore, we report a distinct difference in the patterns of orientation of beta-keratin in the feathers of flying and flightless birds. The trend for increased modulus along the feathers of volant birds is absent in the flightless ostrich.
1
Journal of Structural Biology
54084873
10.1016/J.ACTAMAT.2005.04.048
54,084,873
Structure and mechanical behavior of a toucan beak
Abstract The toucan beak, which comprises one third of the length of the bird and yet only about 1/20th of its mass, has outstanding stiffness. The structure of a Toco toucan (Ramphastos toco) beak was found to be a sandwich composite with an exterior of keratin and a fibrous network of closed cells made of calcium-rich proteins. The keratin layer is comprised of superposed hexagonal scales (50 μm diameter and 1 μm thickness) glued together. Its tensile strength is about 50 MPa and Young’s modulus is 1.4 GPa. Micro and nanoindentation hardness measurements corroborate these values. The keratin shell exhibits a strain-rate sensitivity with a transition from slippage of the scales due to release of the organic glue, at a low strain rate (5 × 10−5/s) to fracture of the scales at a higher strain rate (1.5 × 10−3/s). The closed-cell foam is comprised of fibers having a Young’s modulus twice as high as the keratin shells due to their higher calcium content. The compressive response of the foam was modeled by the Gibson–Ashby constitutive equations for open and closed-cell foam. There is a synergistic effect between foam and shell evidenced by experiments and analysis establishing the separate responses of shell, foam, and foam + shell. The stability analysis developed by Karam and Gibson, assuming an idealized circular cross section, was applied to the beak. It shows that the foam stabilizes the deformation of the beak by providing an elastic foundation which increases its Brazier and buckling load under flexure loading.
1
Acta Materialia
1917972
10.1126/SCIENCE.1195421
1,917,972
How Cats Lap: Water Uptake by Felis catus
Lap Cats We all know that domestic cats lap milk, but perhaps fewer of us have thought about how they do this. Reis et al. (p. 1231, published online 11 November; see the cover) have discovered that cats curl their tongues so that the top surface touches the water. Then, by lifting their tongues rapidly, a column of liquid grows by inertia until gravity induces its breakage and the cats close their jaws to capture the liquid. Lapping frequency is tuned to maximize the volume ingested, depending on the animal's mass; a relationship that holds as true for tabby cats as it does for lions. Cats use fluid inertia to generate a liquid column that they catch in their mouths before gravity destroys it. Animals have developed a range of drinking strategies depending on physiological and environmental constraints. Vertebrates with incomplete cheeks use their tongue to drink; the most common example is the lapping of cats and dogs. We show that the domestic cat (Felis catus) laps by a subtle mechanism based on water adhesion to the dorsal side of the tongue. A combined experimental and theoretical analysis reveals that Felis catus exploits fluid inertia to defeat gravity and pull liquid into the mouth. This competition between inertia and gravity sets the lapping frequency and yields a prediction for the dependence of frequency on animal mass. Measurements of lapping frequency across the family Felidae support this prediction, which suggests that the lapping mechanism is conserved among felines.
1
Science
4431354
10.1038/4401005A
4,431,354
Biomechanics: A pneumo-hydrostatic skeleton in land crabs
Like their aquatic counterparts, terrestrial crabs repeatedly shed their rigid exoskeleton during moulting. But in the case of land crabs, little water is available to provide a temporary hydrostatic skeleton before the new skeleton hardens, and air does not provide the buoyancy necessary to support the animal. Here we show that whenever its exoskeleton is shed, the blackback land crab Gecarcinus lateralis relies on an unconventional type of hydrostatic skeleton that uses both gas and liquid (a ‘pneumo-hydrostat’). To our knowledge, this is the first experimental evidence for a locomotor skeleton that depends on a gas. It establishes a new category of hydrostatic skeletal support and possibly a critical adaptation to life on land for the Crustacea.
1
Nature
34595176
10.1007/S003590050335
34,595,176
Multifocal lenses compensate for chromatic defocus in vertebrate eyes
Abstract The focal length of the vertebrate eye is a function of wavelength, i.e. the eye suffers from longitudinal chromatic aberration. Chromatic defocus is a particularly severe problem in eyes with high light-gathering ability, since depth of field is small due to a pupillary opening that is large in relation to the focal length of the eye. Calculations show that in such eyes only a narrow spectral band of light can be in focus on the retina. For the major part of the visual spectrum, spatial resolution should be limited by the optics of the eye and far lower than the resolving power achievable by the retinal cone photoreceptor mosaic. To solve this problem, fishes with irises unresponsive to light have developed lenses with multiple focal lengths. Well-focused images are created at the wavelengths of maximum absorbance of all spectral cone types. Multifocal lenses also appear to be present in some terrestrial species. In eyes with mobile irises, multifocal lenses are correlated with pupil shapes that allow all zones of the lens, with different refractive powers, to participate in the imaging process, irrespective of the state of pupil constriction.
1
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
206511047
10.1126/SCIENCE.1154117
206,511,047
The Transition from Stiff to Compliant Materials in Squid Beaks
The beak of the Humboldt squid Dosidicus gigas represents one of the hardest and stiffest wholly organic materials known. As it is deeply embedded within the soft buccal envelope, the manner in which impact forces are transmitted between beak and envelope is a matter of considerable scientific interest. Here, we show that the hydrated beak exhibits a large stiffness gradient, spanning two orders of magnitude from the tip to the base. This gradient is correlated with a chemical gradient involving mixtures of chitin, water, and His-rich proteins that contain 3,4-dihydroxyphenyl-l-alanine (dopa) and undergo extensive stabilization by histidyl-dopa cross-link formation. These findings may serve as a foundation for identifying design principles for attaching mechanically mismatched materials in engineering and biological applications.
1
Science
37997482
10.1109/OCEANS-BERGEN.2013.6608113
37,997,482
Whisker-like geometries and their force reduction properties
This paper studies the effects of geometrical features on harbor seal whiskers on its force reduction ability. Each feature in the seal whisker is sequentially stripped from the original whisker shape. Four whisker-like geometries are created from such methodology. 3D simulations of flow around the structures are performed and the resulting forces on the structures are non-dimensionalized. The lift and drag coefficients of these structures are compared to the real whisker case. The undulations on minor and major axes are found to be necessary in reducing the lift forces. Existence of only one of the undulations fails to weaken the flow and break the vortex tubes and braids in the wake. The offset angle between leading edge and trailing edge are found to have slight effects on the lift and drag coefficients. The reduction in drag coefficient is found to be dependent on the existence of undulations in minor axis. The force responses of whisker-like geometries with undulations on one of their axes are found to be periodic. When the force response on whisker-like geometries with both undulations are found to be chaotic. Vortex shedding frequency of the structure is observed to decrease considerably when no offset angle is introduced into the geometry. This may result in longer lifespan of the structure.
1
OCEANS Conference
201617727
10.5897/SRE
201,617,727
Scientific Research and Essays
null
1
Scientific Research and Essay
7740526
10.1016/S0960-9822(02)00806-0
7,740,526
Bacterial Surface Motility: Slime Trails, Grappling Hooks and Nozzles
We thank N. Bose, K. Collins, R. Brennan, T. Economou, H. Higgs, M. Koomey, G. O'Toole, M. Sheetz, J. Skerker, R. Taylor, and T. Yahr for critical discussion of the ideas in this review. We apologize to colleagues whose work was not cited due to space constraints. A.J.M. is supported by Fellowship DRG–1598 of the Cancer Research Fund of the Damon Runyon-Walter Winchell Foundation. K.T.F. is supported by the NIH (GM59721) and the W.M. Keck Foundation.
1
Current Biology
7043372
10.1038/420475A
7,043,372
Animal communication: Tree-hole frogs exploit resonance effects
Animal mating calls that exert a comparatively high sound pressure propagate over greater distances and generally have greater attractive power. Here we show that calling male Bornean tree-hole frogs (Metaphrynella sundana) actively exploit the acoustic properties of cavities in tree trunks that are partially filled with water and which are primarily used as egg-deposition sites. By tuning their vocalizations to the resonant frequency of the hole, which varies with the amount of water that it contains, these frogs enhance their chances of attracting females.
1
Nature
2740822
10.1242/JEB.001545
2,740,822
Mechanics of cutting maneuvers by ostriches (Struthio camelus)
SUMMARY We studied the strategies used by cursorial bipeds (ostriches) to maneuver during running. Eight ostriches were induced to run along a trackway and execute turns. Ground reaction forces and three-dimensional kinematics of the body and leg joints were simultaneously recorded, allowing calculation of joint angles and quasi-static net joint torques. Sidesteps, where the leg on the outside of the turn changes the movement direction, and crossovers using the inside leg, occurred with nearly equal frequency. Ostriches executed maneuvers using a simple control strategy that required minimal changes to leg kinematics or net torque production at individual joints. Although ostriches did use acceleration or braking forces to control body rotation, their morphology allowed for both crossovers and sidesteps to be accomplished with minimal net acceleratory/braking force production. Moreover, body roll and ab/adduction of the leg shifted the foot position away from the turn direction, reducing the acceleratory/braking forces required to prevent under- or over-rotation and aligning the leg with the ground reaction force.
1
The Journal of Experimental Biology
22634337
10.1016/J.ASD.2007.04.001
22,634,337
The anatomy and ultrastructure of the suctorial organ of Solifugae (Arachnida).
Solifugae possess an evertable, adhesive pedipalpal organ (suctorial organ) at the tip of the distal tarsus of each pedipalp that is unique among arachnids. When inverted inside the pedipalp, the suctorial organ is covered with two cuticular lips, a dorsal upper lip and a ventral lower lip, but it can be protruded rapidly in order to facilitate grasping prey or climbing on bushes or even climbing on smooth surfaces due to its remarkable adhesive properties. In this study, the suctorial organs of different species from old world families Galeodidae and Karschiidae and new world families Ammotrechidae and Eremobatidae were investigated by means of light microscopy, scanning and transmission electron microscopy. In all representatives, the suctorial organ is formed by an evertable, cuticular pad with a complex internal stabilizing structure. The procuticle of this pad consists of a lattice-like basal plate and numerous stalked structures connected to this basal plate. The shafts of the stalked structures are regularly organized and ramify apically. The surface of the suctorial organ is constituted of a very thin epicuticle overlaying the ramifying apices forming ridges and furrows on the ventral side of the suctorial organ.
1
Arthropod Structure & Development
34626840
10.1126/SCIENCE.202.4369.747
34,626,840
Shark Skin: Function in Locomotion
Hydrostatic pressure under the skin of sharks varies with swimming speed. Stress in the skin varies with the internal pressure, and the skin stress controls skin stiffness. Locomotory muscles attach to the skin which is thus a whole-body exotendon whose mechanical advantage in transmitting muscular contraction is greater than that of the endoskeleton.
1
Science
37096721
10.1093/OXFORDJOURNALS.BMB.A070614
37,096,721
The insect cuticle and membrane structure.
null
1
British Medical Bulletin
96949737
10.1080/00218460902996358
96,949,737
Polyphosphoprotein-Containing Marine Adhesives
Protein phosphorylation is an important regulator of both cellular and extracellular events. Recently, protein phosphorylation has also emerged as an important process in biological adhesives. During the last decade, Herbert Waite and his group have indeed characterized several polyphosphoproteins from the adhesive secretions of two different marine organisms, mussels and tube-building worms. This suggests the possibility that polyphosphoproteins could be important components of several bioadhesives and may, therefore, be widely distributed throughout the animal kingdom. Many amino acids can be targets for phosphorylation but only phosphoserine (pSer) has been detected to date in marine adhesive proteins. We investigated whether monoclonal antibodies directed against pSer could be used to specifically label polyphosphoproteins in marine adhesives. Antibodies were applied on histological sections through the foot of the mussel Mytilus edulis and through the building organ of the tube-worm Sabellaria alveolata. In both cases, anti-pSer binding was detected in the adhesive glands (phenol gland and cement gland, respectively). However, the intensity of the immunolabeling was different between the two species, being weak in the former and strong in the latter. With the use of these antibodies, a new pSer-rich bioadhesive has been detected in Cuvierian tubules, the sticky defense organs of sea cucumbers. Immunoblots and amino acid analyses confirmed the presence of polyphosphoproteins in the adhesive secretion of the Cuvierian tubules from three species of sea cucumber. These findings bring to three the number of animal groups in which adhesive processes involve polyphosphoproteins and raise interesting questions about the convergent evolution of these adhesives.
1
Journal of Adhesion
7034585
10.1242/JEB.073809
7,034,585
Self-cleaning in tree frog toe pads; a mechanism for recovering from contamination without the need for grooming
SUMMARY Tree frogs use adhesive toe pads for climbing on a variety of surfaces. They rely on wet adhesion, which is aided by the secretion of mucus. In nature, the pads will undoubtedly get contaminated regularly through usage, but appear to maintain their stickiness over time. Here, we show in two experiments that the toe pads of White's tree frogs (Litoria caerulea) quickly recover from contamination through a self-cleaning mechanism. We compared adhesive forces prior to and after contamination of (1) the whole animal on a rotatable platform and (2) individual toe pads in restrained frogs mimicking individual steps using a motorised stage. In both cases, the adhesive forces recovered after a few steps but this took significantly longer in single toe pad experiments from restrained frogs, showing that use of the pads increases recovery. We propose that both shear movements and a ‘flushing’ effect of the secreted mucus play an important role in shedding particles/contaminants.
1
The Journal of Experimental Biology
94550302
10.2138/AM-2004-0704
94,550,302
Ultrastructure, aggregation-state, and crystal growth of biogenic nanocrystalline sphalerite and wurtzite
Abstract In this study, we investigated the size, submicrometer-scale structure, and aggregation state of ZnS formed by sulfate-reducing bacteria (SRB) in a SRB-dominated biofilm growing on degraded wood in cold (T ~ 8 °C), circumneutral-pH (7.2−8.5) waters draining from an abandoned, carbonate-hosted Pb-Zn mine. High-resolution transmission electron microscope (HRTEM) data reveal that the earliest biologically induced precipitates are crystalline ZnS nanoparticles 1−5 nm in diameter. Although most nanocrystals have the sphalerite structure, nanocrystals of wurtzite are also present, consistent with a predicted size dependence for ZnS phase stability. Nearly all the nanocrystals are concentrated into 1−5 μm diameter spheroidal aggregates that display concentric banding patterns indicative of episodic precipitation and flocculation. Abundant disordered stacking sequences and faceted, porous crystalaggregate morphologies are consistent with aggregation-driven growth of ZnS nanocrystals prior to and/or during spheroid formation. Spheroids are typically coated by organic polymers or associated with microbial cellular surfaces, and are concentrated roughly into layers within the biofilm. Size, shape, structure, degree of crystallinity, and polymer associations will all impact ZnS solubility, aggregation and coarsening behavior, transport in groundwater, and potential for deposition by sedimentation. Results presented here reveal nanometer- to micrometer-scale attributes of biologically induced ZnS formation likely to be relevant to sequestration via bacterial sulfate reduction (BSR) of other potential contaminant metal(loid)s, such as Pb2+, Cd2+, As3+ and Hg2+, into metal sulfides. The results highlight the importance of basic mineralogical information for accurate prediction and monitoring of long-term contaminant metal mobility and bioavailability in natural and constructed bioremediation systems. Our observations also provoke interesting questions regarding the role of size-dependent phase stability in biomineralization and provide new insights into the origin of submicrometer- to millimeter-scale petrographic features observed in low-temperature sedimentary sulfide ore deposits.
1
American Mineralogist
10439797
10.1021/JA907063Z
10,439,797
Mechanism of calcite co-orientation in the sea urchin tooth.
Sea urchin teeth are remarkable and complex calcite structures, continuously growing at the forming end and self-sharpening at the mature grinding tip. The calcite (CaCO(3)) crystals of tooth components, plates, fibers, and a high-Mg polycrystalline matrix, have highly co-oriented crystallographic axes. This ability to co-orient calcite in a mineralized structure is shared by all echinoderms. However, the physico-chemical mechanism by which calcite crystals become co-oriented in echinoderms remains enigmatic. Here, we show differences in calcite c-axis orientations in the tooth of the purple sea urchin ( Strongylocentrotus purpuratus ), using high-resolution X-ray photoelectron emission spectromicroscopy (X-PEEM) and microbeam X-ray diffraction (muXRD). All plates share one crystal orientation, propagated through pillar bridges, while fibers and polycrystalline matrix share another orientation. Furthermore, in the forming end of the tooth, we observe that CaCO(3) is present as amorphous calcium carbonate (ACC). We demonstrate that co-orientation of the nanoparticles in the polycrystalline matrix occurs via solid-state secondary nucleation, propagating out from the previously formed fibers and plates, into the amorphous precursor nanoparticles. Because amorphous precursors were observed in diverse biominerals, solid-state secondary nucleation is likely to be a general mechanism for the co-orientation of biomineral components in organisms from different phyla.
1
Journal of the American Chemical Society
7270553
10.1080/00218460902996457
7,270,553
Glueomics: An Expression Survey of the Adhesive Gland of the Sandcastle Worm
Random clones were sequenced from a cDNA library constructed from the adhesive gland of Phragmatopoma californica, a marine polycheate that builds protective shells by gluing together sand grains and biogenic mineral fragments. As many as 14 new proteins and two phenoloxidase enzymes were found that may be structural components of or involved in processing the bioadhesive. Glue protein classification was based on the following criteria: (i) the presence of predicted secretion signal peptides, (ii) low complexity sequences, (iii) strongly skewed amino acid compositions enriched with G, Y, K, H, A, or S, (iv) repeating peptide motifs, and (v) homology to known glue proteins, other structural proteins, or enzymes. The new genes provide probes for further characterization of the adhesive gland as well as potential biotechnological resources and insight.
1
Journal of Adhesion
12221892
10.1242/JEB.076836
12,221,892
Structure, innervation and response properties of integumentary sensory organs in crocodilians
SUMMARY Integumentary sensory organs (ISOs) are densely distributed on the jaws of crocodilians and on body scales of members of the families Crocodilidae and Gavialidae. We examined the distribution, anatomy, innervation and response properties of ISOs on the face and body of crocodilians and documented related behaviors for an alligatorid (Alligator mississippiensis) and a crocodylid (Crocodylus niloticus). Each of the ISOs (roughly 4000 in A. mississippiensis and 9000 in C. niloticus) was innervated by networks of afferents supplying multiple different mechanoreceptors. Electrophysiological recordings from the trigeminal ganglion and peripheral nerves were made to isolate single-unit receptive fields and to test possible osmoreceptive and electroreceptive functions. Multiple small (<0.1 mm2) receptive fields, often from a single ISO, were recorded from the premaxilla, the rostral dentary, the gingivae and the distal digits. These responded to a median threshold of 0.08 mN. The less densely innervated caudal margins of the jaws had larger receptive fields (>100 mm2) and higher thresholds (13.725 mN). Rapidly adapting, slowly adapting type I and slowly adapting type II responses were identified based on neuronal responses. Several rapidly adapting units responded maximally to vibrations at 20–35 Hz, consistent with reports of the ISOs' role in detecting prey-generated water surface ripples. Despite crocodilians' armored bodies, the ISOs imparted a mechanical sensitivity exceeding that of primate fingertips. We conclude that crocodilian ISOs have diverse functions, including detection of water movements, indicating when to bite based on direct contact of pursued prey, and fine tactile discrimination of items held in the jaws.
1
The Journal of Experimental Biology
27985880
10.1002/CMDC.201100252
27,985,880
Bromophycolide A Targets Heme Crystallization in the Human Malaria Parasite Plasmodium falciparum
Plasmodium falciparum, the most deadly human malaria parasite, poses a major threat to human health worldwide, with over 500 million clinical cases and between one and two million deaths annually.[1] Natural products and their synthetic derivatives have provided a significant number of successful antimalarial treatments to date, representing approximately 65 % of current drugs.[2] Quinine, discovered from cinchona tree bark, has been used to treat malaria for centuries and was the primary antimalarial drug until it was replaced by chloroquine, a synthetic derivative, in the 1940s.[3] Chloroquine became the mainstay antimalarial until resistant strains began to appear nearly a decade after its introduction. Artemisinin, isolated from the plant Artemisia annua used in traditional Chinese medicine, ushered in a new wave of antimalarials and became the most potent and rapid-acting drug available.[4] Several synthetic artemisinin derivatives have since been developed, and artemisinin-based combination therapies are currently in use throughout the world to treat this parasitic disease. However, artemisinin-resistant strains have recently been reported,[5] and new antiparasitic drugs are urgently needed to combat these strains.
1
ChemMedChem
20146931
10.1007/B98314
20,146,931
Pheromone Reception
Insects are analytical chemists par excellence. They perceive the world through semiochemicals with inordinate sensitivity.A male moth, for example, can detect a “scent of woman,” i.e., a female-produced sex pheromone, even when the signal-to-noise ratio is very low. In a sense the antennae are “signal translators.” The chemicals signals are “translated” into the language of the brain (nerve impulses or spikes) by an array of sensilla mainly located on the antennae. This information is conveyed to the brain for further processing. Chemical ecologists utilize insect antennae as biosensors for the identification of pheromones and other semiochemicals. The insect olfactory system is also highly selective, able to discriminate natural pheromones from molecules with minimal structural changes. In some cases, one stereoisomer functions as an attractant sex pheromone and its antipode is a behavioral antagonist (inhibitory signal). The specificity of the olfactory system seems to be achieved by two layers of filters. The first level of discrimination is determined by odorantbinding proteins (OBPs) that assist the hydrophobic pheromones to cross an aqueous barrier and reach their receptors. Both OBP and odorant receptor (OR) contribute to the specificity of the cell response and lead to the remarkable selectivity of the insect olfactory system. The members of the OBP-gene family, encoding the encapsulins, form a large group with olfactory and non-olfactory proteins. While the functions of many members of the family are yet to be determined, there is solid evidence for the mode of action of OBPs. Pheromones (and other semiochemicals) enter the sensillar lymph through pore tubules in the cuticle (sensillar wall), are solubilized upon being encapsulated by odorant-binding proteins, and transported to the olfactory receptors. Bound pheromone molecules are protected Topics in Current Chemistry (2005) 240: 1– 36 DOI 10.1007/b98314 © Springer-Verlag Berlin Heidelberg 2005 from odorant-degrading enzymes. Upon interaction with negatively-charged sites at the dendritic membrane, the OBP-ligand complex undergoes a conformational change that leads to the ejection of pheromone. Direct activation of odorant receptors by odorant molecules initiates a cascade of events leading to the generation of spikes. Reverse chemical ecology is a new concept for the screening of attractants based on the binding ability of OBPs to test
1
The Chemistry of Pheromones and other Semiochemicals II; Journal of Chemical Ecology
38218848
10.1088/1748-3182/9/3/031002
38,218,848
Nature's moisture harvesters: a comparative review.
Nature has adapted different methods for surviving dry, arid, xeric conditions. It is the focus of this comparative review to pull together the relevant information gleaned from the literature that could be utilized to design moisture harvesting devices informed by biomimetics. Most water harvesting devices in current use are not informed by nature and those that do are usually based on a biomimetic principle that has been based on one species only. This review draws on the published literature to establish a list of species (animals (vertebrates/invertebrates) and plants) whose habitat is in mainly dry or arid regions and that are known to harvest airborne moisture. Key findings have been outlined and review comments and discussion set out. Following this, surface feature convergences have been identified, namely hexagonal microstructures, groove-like and cone-like geometries. This has been coupled with direction of water flow that is driven by surface energy. As far as the authors are aware, this convergent evolution has not been brought together in this manner before. In the future this information could be translated into an engineered device for collecting water from airborne sources.
1
Bioinspiration & Biomimetics
4420437
10.1038/35286
4,420,437
Worms bask in extreme temperatures
Temperature is one of the most important environmental factors that governs a species' distribution. Some highly specialized prokaryotes can grow at temperatures above 113 °C (ref. 1), but eukaryotes appear less versatile and do not normally occur above 55 °C. Here we show that a colony-dwelling polychaete worm, inhabiting deep-sea hydrothermal vent chimneys, regularly experiences temperatures above 80 °C and a thermal gradient of 60 °C or more over its body length.
1
Nature
3194027
10.1206/701.1
3,194,027
Nests, Petal Usage, Floral Preferences, and Immatures of Osmia (Ozbekosmia) avosetta (Megachilidae: Megachilinae: Osmiini), Including Biological Comparisons with Other Osmiine Bees
Abstract Herein we describe the nests (including construction, closure, orientation, and depth of cells) of the bee Osmia (Ozbekosmia) avosetta Warncke found nesting near Antalya, Turkey, and Sepidan, Iran. Cells are unusual in that they are lined by two layers of colorful flower petals that sandwich a thin middle layer of mud. Analyses of pollen taken from scopal hairs of specimens from the Turkish site were identified as solely from Onobrychis viciifolia Scop. (Fabaceae) whereas those from the Iranian site were from a related plant, Hedysarum elymaiticum Boiss. and Hausskn. These facts coupled with analyses of scopal pollen from 11 other sites in Turkey, Jordan, and Syria strongly suggest that this bee is oligolectic with respect to the plant tribe Hedysareae. The egg and last larval instar of Osmia avosetta are described. The presence of an egg taken from a cell and provisionally identified as belonging to Sapyga pulcherrima Morawitz suggests that this cleptoparasite may have this bee as one of its hosts. In addition, we report new information on and review published accounts concerning the use of whole petals or large petal pieces in the construction of cell walls of osmiine bees. Only Osmia (Ozbekosmia) avosetta and species of Osmia (Tergosmia) have three-layered cell walls with the middle layer made of mud. Recorded also are the similarities and differences exhibited in pollen and petal preferences and nest characteristics of species in these two related subgenera.
1
American Museum Novitates
84986764
10.1071/MF97051
84,986,764
Occurrence of ultraviolet radiation-absorbing mycosporine-like amino acids in coral mucus and whole corals of French Polynesia
Specimens of six scleractinian species were gathered during the austral spring (October–November) 1994 on the external slope of the barrier reef of Arue, Tahiti, and in the lagoon of Arutua, a Tuamotu island. Mucus of each specimen was collected and the optical density and volume excreted were measured. After treatment, mucus was analysed for mycosporine-like amino acids (MAAs) by high-performance liquid chromatography (HPLC). Nine UV-absorbing compounds were present in coral mucus at concentrations between 1 and 500 ng g-1 mucus. Palythine and mycosporine–gly were found in all mucus studied. Mycosporine–2glycine was recovered in 71% of specimens and shinorine in 28%. Porphyra-334 and palythinol were identified as minor MAAs. Three recently identified MAAs, palythine–serine, mycosporine–methylamine:serine and mycosporine–methylamine:threonine, were also found in mucus from Pocillopora. Within a genus, there was a qualitative similarity in MAAs determined by HPLC, irrespective of locality. Values for optical density of the mucus showed the ability of MAAs to protect the animal host and endosymbiotic algae from UV-solar flux and, as inferred from the recent literature, from oxidative forms of oxygen (HO2 . , O 2 - , HO.) derived from photosynthesis.
1
Marine and Freshwater Research
25751114
10.1073/PNAS.1000557107
25,751,114
Solutes determine the temperature windows for microbial survival and growth
Microbial cells, and ultimately the Earth's biosphere, function within a narrow range of physicochemical conditions. For the majority of ecosystems, productivity is cold-limited, and it is microbes that represent the failure point. This study was carried out to determine if naturally occurring solutes can extend the temperature windows for activity of microorganisms. We found that substances known to disorder cellular macromolecules (chaotropes) did expand microbial growth windows, fungi preferentially accumulated chaotropic metabolites at low temperature, and chemical activities of solutes determined microbial survival at extremes of temperature as well as pressure. This information can enhance the precision of models used to predict if extraterrestrial and other hostile environments are able to support life; furthermore, chaotropes may be used to extend the growth windows for key microbes, such as saprotrophs, in cold ecosystems and manmade biomes.
1
Proceedings of the National Academy of Sciences of the United States of America
10401406
10.1242/JEB.044149
10,401,406
A novel stiffening factor inducing the stiffest state of holothurian catch connective tissue
SUMMARY The dermis of sea cucumbers is a catch connective tissue or mutable collagenous tissue that shows large changes in stiffness. Extensive studies on the dermis revealed that it can adopt three different states having different mechanical properties that can be reversibly converted. These are the stiff, standard and soft states. The standard state is readily produced when a dermal piece is immersed in the sea water containing Ca2+, whereas the soft state can be produced by removal of Ca2+. A stiffening protein, tensilin, has been isolated from some sea cucumbers (Cucumaria frondosa and Holothuria leucospilota). Although tensilin converts the state of the dermis from soft to standard, it cannot convert from standard to stiff. In this study, we isolated and partially purified a novel stiffening factor from the dermis of Holothuria leucospilota. The factor stiffened the dermis in normal artificial sea water (ASW) but did not stiffen the soft dermis in Ca2+-free ASW. It also stiffened the dermis that had been converted to the standard state in Ca2+-free ASW by the action of tensilin. These results suggest that the factor produces the stiff dermis from the standard state but cannot work as a stiffener on the soft dermis. Its addition to longitudinal muscles of the sea cucumber produced no effects, suggesting that its effect is specific to the catch connective tissue. Its stiffening activity was susceptible to trypsin, meaning that it is a polypeptide, and its molecular mass estimated from gel filtration chromatography was 2.4 kDa.
1
The Journal of Experimental Biology
22855337
10.2307/1542262
22,855,337
Causes and Consequences of Fluctuating Coelomic Pressure in Sea Urchins.
We measured coelomic pressure in sea urchins to determine whether it was high enough to support a pneu hypothesis of growth. In Strongylocentrotus purpuratus the pressure was found to fluctuate rhythmically about a mean of -8 Pa, and was negative for 70% of the time. This is at variance with the theoretically required positive pressures of the pneu hypothesis. Furthermore, there were no sustained significant differences between the pressure patterns of fed and starved urchins, presumed to be growing and not growing, respectively. The rhythmical fluctuations in pressure were caused by movements of the lantern which changed the curvature and tension of the peristomial membrane. We developed a mathematical and morphological model relating lantern movements, membrane tension, and pressure, that correctly predicts the magnitude of the fluctuations. Pressures predicted by the model depend also on coelomic volume changes. In Lytechinus variegatus simultaneous retraction of the podia, which causes expansion of the ampullae, resulted in an 8.8 Pa increase in coelomic pressure, relative to the pressure during simultaneous podial protraction.
1
The Biological Bulletin
6803811
10.1038/NRMICRO842
6,803,811
Magnetosome formation in prokaryotes
Magnetotactic bacteria were discovered almost 30 years ago, and for many years and many different reasons, the number of researchers working in this field was few and progress was slow. Recently, however, thanks to the isolation of new strains and the development of new techniques for manipulating these strains, researchers from several laboratories have made significant progress in elucidating the molecular, biochemical, chemical and genetic bases of magnetosome formation and understanding how these unique intracellular organelles function. We focus here on this progress.
1
Nature Reviews Microbiology
53183911
10.1016/J.ANBEHAV.2009.11.035
53,183,911
Emergency networking: famine relief in ant colonies
Resource distribution is fundamental to social organization, but it poses a dilemma. How to facilitate the spread of useful resources but restrict harmful substances? This dilemma reaches a zenith in famine relief. Survival depends on distributing food fast but that could increase vulnerability to poisons. We tested how Temnothorax albipennis ants solve this dilemma in the distribution of honey solution after 48 h of starvation in four colonies with individually marked workers. We constructed the complete network of liquid food transmission (trophallaxis) between individuals. Within the first 30 min of famine relief, 95% of the workers received food and the distribution rate was an order of magnitude faster compared to the controls. We tested the assumptions of a simple analytical model that best fitted our data. Good mixing during famine relief was facilitated by the movement of internal workers away from the brood pile and the movement of foragers with food away from the nest entrance. This is intriguing because T. albipennis workers have spatial fidelity zones and in the controls internal and external workers were segregated. We discovered that colony vulnerability to poisons during famine relief might be mitigated by: (1) the dilution of food from the same source through mixing, (2) the concentration of food in workers positioned midway between the colony centre and its periphery and (3) the existence of living 'silos'. The latter are expendable foragers, who stay inside the nest and store food during famine relief, thus acting as potential disposable testers for food toxicity. © 2009 The Association for the Study of Animal Behaviour.
1
Animal Behaviour
17405225
10.1126/SCIENCE.1223304
17,405,225
How the Cucumber Tendril Coils and Overwinds
Curls Beget More Curls Cucumber tendrils reach up to find an attachment, and then coil to shorten and drag the plant up toward the sunlight. Gerbode et al. (p. 1087) analyzed the biomechanics of cucumber tendril coiling. The process depends on a thin layer of cells within the tendril that becomes lignified during the coiling process. A construct of pre-strained silicon sheets, fabric ribbon, and copper wire reproduced the coiling functions in abiotic materials. Physical and mathematical models explained the peculiar response by which the cucumber tendril initially overwinds when pulled further. Plants climb via lifelines that are a mix of strength and flexibility. The helical coiling of plant tendrils has fascinated scientists for centuries, yet the underlying mechanism remains elusive. Moreover, despite Darwin’s widely accepted interpretation of coiled tendrils as soft springs, their mechanical behavior remains unknown. Our experiments on cucumber tendrils demonstrate that tendril coiling occurs via asymmetric contraction of an internal fiber ribbon of specialized cells. Under tension, both extracted fiber ribbons and old tendrils exhibit twistless overwinding rather than unwinding, with an initially soft response followed by strong strain-stiffening at large extensions. We explain this behavior using physical models of prestrained rubber strips, geometric arguments, and mathematical models of elastic filaments. Collectively, our study illuminates the origin of tendril coiling, quantifies Darwin’s original proposal, and suggests designs for biomimetic twistless springs with tunable mechanical responses.
1
Science
37468580
10.1038/246313A0
37,468,580
Energetic Cost of Locomotion in Kangaroos
THE hopping of kangaroos is reminiscent of a bouncing ball or the action of a pogo stick. This suggests a significant storage and recovery of energy in elastic elements. One might surmise that the kangaroo's first hop would require a large amount of energy whereas subsequent hops could rely extensively on elastic rebound. If this were the case, then the kangaroo's unusual saltatory mode of locomotion should be an energetically inexpensive way to move.
1
Nature
15133107
10.1093/MOLBEV/MSM124
15,133,107
Signatures of functional constraint at aye-aye opsin genes: the potential of adaptive color vision in a nocturnal primate.
While color vision perception is thought to be adaptively correlated with foraging efficiency for diurnal mammals, those that forage exclusively at night may not need color vision nor have the capacity for it. Indeed, although the basic condition for mammals is dichromacy, diverse nocturnal mammals have only monochromatic vision, resulting from functional loss of the short-wavelength sensitive opsin gene. However, many nocturnal primates maintain intact two opsin genes and thus have dichromatic capacity. The evolutionary significance of this surprising observation has not yet been elucidated. We used a molecular population genetics approach to test evolutionary hypotheses for the two intact opsin genes of the fully nocturnal aye-aye (Daubentonia madagascariensis), a highly unusual and endangered Madagascar primate. No evidence of gene degradation in either opsin gene was observed for any of 8 aye-aye individuals examined. Furthermore, levels of nucleotide diversity for opsin gene functional sites were lower than those for 15 neutrally evolving intergenic regions (>25 kb in total), which is consistent with a history of purifying selection on aye-aye opsin genes. The most likely explanation for these findings is that dichromacy is advantageous for aye-ayes despite their nocturnal activity pattern. We speculate that dichromatic nocturnal primates may be able to perceive color while foraging under moonlight conditions, and suggest that behavioral and ecological comparisons among dichromatic and monochromatic nocturnal primates will help to elucidate the specific activities for which color vision perception is advantageous.
1
Molecular Biology and Evolution
15278216
10.1111/J.1469-7580.2006.00648.X
15,278,216
The structure of the cushions in the feet of African elephants (Loxodonta africana)
The uniquely designed limbs of the African elephant, Loxodonta africana, support the weight of the largest terrestrial animal. Besides other morphological peculiarities, the feet are equipped with large subcutaneous cushions which play an important role in distributing forces during weight bearing and in storing or absorbing mechanical forces. Although the cushions have been discussed in the literature and captive elephants, in particular, are frequently affected by foot disorders, precise morphological data are sparse. The cushions in the feet of African elephants were examined by means of standard anatomical and histological techniques, computed tomography (CT) and magnetic resonance imaging (MRI). In both the forelimb and the hindlimb a 6th ray, the prepollex or prehallux, is present. These cartilaginous rods support the metacarpal or metatarsal compartment of the cushions. None of the rays touches the ground directly. The cushions consist of sheets or strands of fibrous connective tissue forming larger metacarpal/metatarsal and digital compartments and smaller chambers which were filled with adipose tissue. The compartments are situated between tarsal, metatarsal, metacarpal bones, proximal phalanges or other structures of the locomotor apparatus covering the bones palmarly/plantarly and the thick sole skin. Within the cushions, collagen, reticulin and elastic fibres are found. In the main parts, vascular supply is good and numerous nerves course within the entire cushion. Vater–Pacinian corpuscles are embedded within the collagenous tissue of the cushions and within the dermis. Meissner corpuscles are found in the dermal papillae of the foot skin. The micromorphology of elephant feet cushions resembles that of digital cushions in cattle or of the foot pads in humans but not that of digital cushions in horses. Besides their important mechanical properties, foot cushions in elephants seem to be very sensitive structures.
1
Journal of Anatomy
4452265
10.1016/J.JMBBM.2016.10.001
4,452,265
A comparative study of piscine defense: The scales of Arapaima gigas, Latimeria chalumnae and Atractosteus spatula.
We compare the characteristics of the armored scales of three large fish, namely the Arapaima gigas (arapaima), Latimeria chalumnae (coelacanth), and Atractosteus spatula (alligator gar), with specific focus on their unique structure-mechanical property relationships and their specialized ability to provide protection from predatory pressures, with the ultimate goal of providing bio-inspiration for manmade materials. The arapaima has flexible and overlapping cycloid scales which consist of a tough Bouligand-type arrangement of collagen layers in the base and a hard external mineralized surface, protecting it from piranha, a predator with extremely sharp teeth. The coelacanth has overlapping elasmoid scales that consist of adjacent Bouligand-type pairs, forming a double-twisted Bouligand-type structure. The collagenous layers are connected by collagen fibril struts which significantly contribute to the energy dissipation, so that the scales have the capability to defend from predators such as sharks. The alligator gar has inflexible articulating ganoid scales made of a hard and highly mineralized enamel-like outer surface and a tough dentine-like bony base, which resist powerful bite forces of self-predation and attack by alligators. The structural differences between the three scales correspond with the attack of their predators, and show refined mechanisms which may be imitated and incorporated into superior bioinspired and biomimetic designs that are specialized to resist specific modes of predation.
1
Journal of The Mechanical Behavior of Biomedical Materials
206647742
10.1126/SCIENCE.AAF3252
206,647,742
Soil immune responses
Soil microbiomes may be harnessed for plant health Soil microorganisms are central to the provision of food, feed, fiber, and medicine. Engineering of soil microbiomes may promote plant growth and plant health, thus contributing to food security and agricultural sustainability (1, 2). However, little is known about most soil microorganisms and their impact on plant health. Disease-suppressive soils offer microbiome-mediated protection of crop plants against infections by soil-borne pathogens. Understanding of the microbial consortia and mechanisms involved in disease suppression may help to better manage plants while reducing fertilizer and pesticide inputs.
1
Science
2933525
10.1098/RSBL.2004.0269
2,933,525
Distribution of unique red feather pigments in parrots
In many birds, red, orange and yellow feathers are coloured by carotenoid pigments, but parrots are an exception. For over a century, biochemists have known that parrots use an unusual set of pigments to produce their rainbow of plumage colours, but their biochemical identity has remained elusive until recently. Here, we use high-performance liquid chromatography to survey the pigments present in the red feathers of 44 species of parrots representing each of the three psittaciform families. We found that all species used the same suite of five polyenal lipochromes (or psittacofulvins) to colour their plumage red, indicating that this unique system of pigmentation is remarkably conserved evolutionarily in parrots. Species with redder feathers had higher concentrations of psittacofulvins in their plumage, but neither feather colouration nor historical relatedness predicted the ratios in which the different pigments appeared. These polyenes were absent from blood at the time when birds were replacing their colourful feathers, suggesting that parrots do not acquire red plumage pigments from the diet, but instead manufacture them endogenously at growing feathers.
1
Biology Letters
85131656
10.1080/00218460902996788
85,131,656
Crosslinking Lessons From Biology: Enlisting Enzymes for Macromolecular Assembly
Biology is well known for its use of linear polymers to perform sophisticated functions. Nucleic acids store and process genetic information, while proteins perform recognition, transport, and catalytic functions. Biology also employs polymers (especially proteins and polysaccharides) to perform mechanical functions and there are several examples in which biology covalently crosslinks polymers to confer elasticity and strength. In some cases, the crosslinking enzymes have attracted attention as a simple and safe means for macromolecular processing in vitro. Here, we review recent research with two enzymes, tyrosinase and microbial transglutaminase, that are being examined for a variety of applications.
1
Journal of Adhesion
16412781
10.1242/JEB.078931
16,412,781
Flow-dependent porosity and other biomechanical properties of mysticete baleen
SUMMARY Despite its vital function in a highly dynamic environment, baleen is typically assumed to be a static material. Its biomechanical and material properties have not previously been explored. Thus I tested sections of baleen from bowhead whales, Balaena mysticetus, and humpback whales, Megaptera novaeangliae, alone or in groups representing miniature ‘racks’, in a flow tank through which water and buoyant particles circulated with variable flow velocity. Kinematic sequences were recorded through an endoscopic camera or viewing window. One set of experiments investigated particle capture; another series analyzed biomechanical behavior, including fringe spacing, movement and interaction. Baleen fringe porosity directly correlates, in a mostly linear fashion, with velocity of incident water flow. However, undulation and interaction of fringes (especially of bowheads) at higher flow velocities can decrease porosity. Fringe porosity depends on distance from the baleen plate. Porosity also varies, with fringe length, by position along the length of an individual plate. Plate orientation, which varied from 0 to 90 deg relative to water flow, is crucial in fringe spacing and particle capture. At all flow velocities, porosity is lowest with plates aligned parallel to water flow. Turbulence introduced when plates rotate perpendicular to flow (as in cross-flow filtration) increases fringe interaction, so that particles more easily strike fringes yet more readily dislodge. Baleen of bowhead whales, which feed by continuous ram filtration, differs biomechanically from that of humpbacks, which use intermittent lunge filtration. The longer, finer fringes of bowhead baleen readily form a mesh-like mat, especially at higher flow velocities, to trap tiny particles.
1
The Journal of Experimental Biology
16782681
10.1023/A:1020537319805
16,782,681
Odorant-Binding Proteins from a Primitive Termite
Hitherto, odorant-binding proteins (OBPs) have been identified from insects belonging to more highly evolved insect orders (Lepidoptera, Coleoptera, Diptera, Hymenoptera, and Hemiptera), whereas only chemosensory proteins have been identified from more primitive species, such as orthopteran and phasmid species. Here, we report for the first time the isolation and cloning of odorant-binding proteins from a primitive termite species, the dampwood termite, Zootermopsis nevadensis nevadensis (Isoptera: Termopsidae). A major antennae-specific protein was detected by native PAGE along with four other minor proteins, which were also absent in the extract from control tissues (hindlegs). Multiple cDNA cloning led to the full characterization of the major antennae-specific protein (ZnevOBP1) and to the identification of two other antennae-specific cDNAs, encoding putative odorant-binding proteins (ZnevOBP2 and ZnevOBP3). N-terminal amino acid sequencing of the minor antennal bands and cDNA cloning showed that olfaction in Z. n. nevadensis may involve multiple odorant-binding proteins. Database searches suggest that the OBPs from this primitive termite are homologues of the pheromone-binding proteins from scarab beetles and antennal-binding proteins from moths.
1
Journal of Chemical Ecology
12272689
10.1073/PNAS.1016944108
12,272,689
The hummingbird tongue is a fluid trap, not a capillary tube
Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics. Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes. We demonstrate that the hummingbird tongue does not function like a pair of tiny, static tubes drawing up floral nectar via capillary action. Instead, we show that the tongue tip is a dynamic liquid-trapping device that changes configuration and shape dramatically as it moves in and out of fluids. We also show that the tongue–fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap. Our results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds. Our findings have ramifications for the study of feeding mechanics in other nectarivorous birds, and for the understanding of the evolution of nectarivory in general. We propose a conceptual mechanical explanation for this unique fluid-trapping capacity, with far-reaching practical applications (e.g., biomimetics).
1
Proceedings of the National Academy of Sciences of the United States of America
11572826
10.1088/1748-3182/5/3/035001
11,572,826
Nacre from mollusk shells: a model for high-performance structural materials.
Nacre is the iridescent layer found inside a large number of mollusk shells. This natural composite has a very high mineral content, which makes it hard and stiff. However it is the toughness of nacre which is the most impressive: it is three orders of magnitude tougher than the mineral it is made of. No manmade composite material can boast such amplification in toughness, and for this reason nacre has become a biomimetic model material. The mineral in nacre comes in the form of microscopic polygonal tablets, which have the ability to 'slide' on one another in large numbers when the material is loaded in tension. This key mechanism makes nacre a quasi-ductile material, which in turn greatly increases its toughness and makes it damage tolerant. Numerous 'artificial nacres' were developed in the past but none of them can truly duplicate the remarkable mechanism of tablet sliding. In this work selected structural features of nacre were implemented in a PMMA-based composite, which for the first time could replicate the collective tablet sliding mechanism. This material demonstrates that the powerful toughening mechanism operating in natural nacre can be duplicated and harnessed in engineering materials.
1
Bioinspiration & Biomimetics
11118248
10.1104/PP.123.1.29
11,118,248
Solar-powered sea slugs. Mollusc/algal chloroplast symbiosis.
Solar-powered “leaves that crawl”? This description of photosynthetic sea slugs (adapted from Bill Rudman [[www.austmus.gov.au/seaslugs/solarpow.htm][1]] and Robert Trench [1975]) aptly describes the symbiotic association that occurs between certain molluscan sea slugs and algal chloroplasts.
1
Plant Physiology
4027446
10.1371/JOURNAL.PONE.0062682
4,027,446
The Great Silk Alternative: Multiple Co-Evolution of Web Loss and Sticky Hairs in Spiders
Spiders are the most important terrestrial predators among arthropods. Their ecological success is reflected by a high biodiversity and the conquest of nearly every terrestrial habitat. Spiders are closely associated with silk, a material, often seen to be responsible for their great ecological success and gaining high attention in life sciences. However, it is often overlooked that more than half of all Recent spider species have abandoned web building or never developed such an adaptation. These species must have found other, more economic solutions for prey capture and retention, compensating the higher energy costs of increased locomotion activity. Here we show that hairy adhesive pads (scopulae) are closely associated with the convergent evolution of a vagrant life style, resulting in highly diversified lineages of at least, equal importance as the derived web building taxa. Previous studies often highlighted the idea that scopulae have the primary function of assisting locomotion, neglecting the fact that only the distal most pads (claw tufts) are suitable for those purposes. The former observations, that scopulae are used in prey capture, are largely overlooked. Our results suggest the scopulae evolved as a substitute for silk in controlling prey and that the claw tufts are, in most cases, a secondary development. Evolutionary trends towards specialized claw tufts and their composition from a low number of enlarged setae to a dense array of slender ones, as well as the secondary loss of those pads are discussed further. Hypotheses about the origin of the adhesive setae and their diversification throughout evolution are provided.
1
PLOS ONE
86061329
10.1643/0045-8511(2001)001[1114:BSVIHL]2.0.CO;2
86,061,329
Blood-Squirting Variability in Horned Lizards (Phrynosoma)
Abstract Variability within the genus Phrynosoma in the occurrence of ocular-sinus blood-squirting, reportedly a defense used in canid encounters, is reviewed from the literature. Six species have been reported to squirt blood, and seven species remain unreported. Five of the latter species were tested in dog trials; one exhibited blood-squirting (Phrynosoma hernandesi), one exhibited precursor behaviors but failed to squirt blood (Phrynosoma ditmarsi), and three yielded negative results (Phrynosoma mcallii, Phrynosoma modestum, and Phrynosoma platyrhinos). Instances of blood-squirting in response to human encounters were collected and largely support the negative results for the three species P. mcallii, P. modestum, and P. platyrhinos. A phylogeny of blood-squirting and nonblood-squirting species is presented with blood-squirting being plesiomorphic in the genus and the synapomorphic condition of nonsquirting species being restricted to a single clade of P. mcallii-modestum-platyrhinos. The possibility of P. douglasii independently evolving an autapomorphic condition remains unresolved. Dog trials with 40 adult Phrynosoma cornutum were conducted to determine influences of body size and sex on squirt frequency and blood mass expelled, as well as to examine aspects of the potential physiological cost of the defense. In 153 trials, 85% of all lizards squirted in at least one trial, 82% squirted in more than one trial, and two lizards squirted daily over the seven-day trial period. Initial body mass positively correlated with the total number of squirts/individual (r2 = 0.28; P < 0.001) and the number of days a lizard continued squirting (r2 = 0.63; P < 0.01). Number of squirts/individual/day declined over the seven-day trial period (r2 = 0.20; P < 0.05). Cumulative mass loss for individual lizards attributable to blood-squirting averaged 0.7 ± 0.8 g (2.0 ± 2.0% body mass), with a high of 2.8 g (6.8% body mass). In addition, juvenile P. cornutum and P. hernandesi were shown to squirt blood in dog trials, illustrating the early developmental onset of the behavior.
1
Copeia
2110180
10.3354/MEPS08868
2,110,180
Drag reduction by air release promotes fast ascent in jumping emperor penguins—a novel hypothesis
To jump out of water onto sea ice, emperor penguins must achieve sufficient underwa- ter speed to overcome the influence of gravity when they leave the water. The relevant combination of density and kinematic viscosity of air is much lower than for water. Injection of air into boundary layers ('air lubrication') has been used by engineers to speed movement of vehicles (ships, torpedoes) through sea water. Analysis of published and unpublished underwater film leads us to present a hypothesis that free-ranging emperor penguins employ air lubrication in achieving high, probably maximal, underwater speeds (mean ± SD: 5.3 ± 1.01 m s -1 ), prior to jumps. Here we show evidence that penguins dive to 15 to 20 m with air in their plumage and that this compressed air is released as the birds subsequently ascend whilst maintaining depressed feathers. Fine bubbles emerge continu- ously from the entire plumage, forming a smooth layer over the body and generating bubbly wakes behind the penguins. In several hours of film of hundreds of penguins, none were seen to swim rapidly upwards without bubbly wakes. Penguins descend and swim horizontally at about 2 m s -1 ; from simple physical models and calculations presented, we hypothesize that a significant proportion of the enhanced ascent speed is due to air lubrication reducing frictional and form drag, that buoyancy forces alone cannot explain the observed speeds, and that cavitation plays no part in bubble formation.
1
Marine Ecology Progress Series
8389046
10.1007/S00114-008-0472-Y
8,389,046
Rheum palaestinum (desert rhubarb), a self-irrigating desert plant
The rare plant Rheum palaestinum (Polygonaceae) is a perennial hemicryptophyte that grows during the rainy winter in desert mountainous areas in Israel and Jordan that receive an average annual rainfall of ca. 75 mm. It produces between one and four large round leaves that are tightly attached to the ground and form large rosettes of up to 1 m2. These leaves differ markedly from the typical small leaves of most desert plants. Moreover, they have a unique 3D morphology resembling a scaled-down mountainous area with well-developed steep drainage systems, raising the question which selective agents were involved in their evolution. We propose that the large leaves collect rainwater that then infiltrates the soil surrounding the root. We measured the seasonal course of leaf growth, examined the area of wet soil surrounding the root after actual and simulated rain, and modeled the water harvesting capacity using the plant leaf area and the weekly precipitation. We show that even in the slightest rains, water flows above the veins to the leaf’s base where it irrigates the vertical root. A typical plant harvests more than 4,100 cm3 of water per year, and enjoys a water regime of about 427 mm/year, equivalent to the water supply in a Mediterranean climate. This is the first example of self-irrigation by large leaves in a desert plant, creating a leaf-made mini oasis.
1
Naturwissenschaften
4370362
10.1038/NATURE02435
4,370,362
Convergent evolution in mechanical design of lamnid sharks and tunas
The evolution of ‘thunniform’ body shapes in several different groups of vertebrates, including whales, ichthyosaurs and several species of large pelagic fishes supports the view that physical and hydromechanical demands provided important selection pressures to optimize body design for locomotion during vertebrate evolution. Recognition of morphological similarities between lamnid sharks (the most well known being the great white and the mako) and tunas has led to a general expectation that they also have converged in their functional design; however, no quantitative data exist on the mechanical performance of the locomotor system in lamnid sharks. Here we examine the swimming kinematics, in vivo muscle dynamics and functional morphology of the force-transmission system in a lamnid shark, and show that the evolutionary convergence in body shape and mechanical design between the distantly related lamnids and tunas is much more than skin deep; it extends to the depths of the myotendinous architecture and the mechanical basis for propulsive movements. We demonstrate that not only have lamnids and tunas converged to a much greater extent than previously known, but they have also developed morphological and functional adaptations in their locomotor systems that are unlike virtually all other fishes.
1
Nature
30529544
10.1016/J.TOXICON.2008.04.163
30,529,544
Neutralization of lethality and proteolytic activities of Malayan pit viper (Calloselasma rhodostoma) venom with North American Virginia opossum (Didelphis virginiana) serum.
Malayan pit viper (Calloselasma rhodostoma) envenomation is a major health problem in South East Asia. During envenomation, venom components mainly affect the hemostatic system. The sera from the North American Virginia opossums (Didelphis virginiana) were able to neutralize the venom of the Malayan pit viper. These natural inhibitors could be explored as potential therapeutics against envenomations of a variety of venomous snake species in different geographical habitats.
1
Toxicon
41091795
10.1006/JTBI.1999.0959
41,091,795
Heat transfer through penguin feathers
Morphological measurements of penguin feathers are used to construct a thermal model of heat transfer through the coat. Assuming uniform distribution of the feathers and their associated afterfeathers, it is possible to model heat transfer through the coat of the penguin using standard theory. It is shown that convection does not occur in the coat of the penguin and that radiative heat loss is minimized. The theory predicts a thermal conductivity of 2.38 W m(-2)K(-1)which compares well with an empirically measured value of 1.93 W m(-2)K(-1). Copyright 1999 Academic Press.
1
Journal of Theoretical Biology
56428995
10.1007/978-1-4612-4018-1_14
56,428,995
Organisms as ecosystem engineers
Interactions between organisms are a major determinant of the distribution and abundance of species. Ecology textbooks (e.g., Ricklefs 1984, Krebs 1985, Begon et al. 1990) summarise these important interactions as intra- and interspecific competition for abiotic and biotic resources, predation, parasitism and mutualism. Conspicuously lacking from the list of key processes in most text books is the role that many organisms play in the creation, modification and maintenance of habitats. These activities do not involve direct trophic interactions between species, but they are nevertheless important and common. The ecological literature is rich in examples of habitat modification by organisms, some of which have been extensively studied (e.g. Thayer 1979, Naiman et al. 1988).
1
Oikos
84301906
10.1016/0022-0981(92)90238-6
84,301,906
Alternation between attachment mechanisms by limpets in the field
The attachment mechanism used by limpets in the rocky, wave-swept intertidal zone of California was determined during high tide and low tide. The two mechanisms that limpets are known to use, suction and glue-like adhesion, were distinguished by measuring the limpets' attachment forces in shear and by staining for glue-like residues where the limpets had been attached. The results show that ≈ 73% of limpets at high tide use suction, while the rest use glue-like adhesion. Conversely, ≈ 75% of limpets at low tide use glue-like adhesion, while the rest use suction. The normal tenacity of limpets was also measured at high and low tide. The mean tenacity at high tide was significantly less than that at low tide. From these data it was estimated that the mean tenacity of glue-like adhesion is ≈ 0.23 MN·m−2 and the mean tenacity of suction adhesion is ≈ 0.09 MN·m−2. It is hypothesized that the cycle of alternating attachment mechanisms is linked to the limpets foraging cycles.
1
Journal of Experimental Marine Biology and Ecology
2510221
10.1088/1748-3182/6/1/016003
2,510,221
A mechanical analysis of woodpecker drumming and its application to shock-absorbing systems.
A woodpecker is known to drum the hard woody surface of a tree at a rate of 18 to 22 times per second with a deceleration of 1200 g, yet with no sign of blackout or brain damage. As a model in nature, a woodpecker is studied to find clues to develop a shock-absorbing system for micromachined devices. Its advanced shock-absorbing mechanism, which cannot be explained merely by allometric scaling, is analyzed in terms of endoskeletal structures. In this analysis, the head structures (beak, hyoid, spongy bone, and skull bone with cerebrospinal fluid) of the golden-fronted woodpecker, Melanerpes aurifrons, are explored with x-ray computed tomography images, and their shock-absorbing mechanism is analyzed with a mechanical vibration model and an empirical method. Based on these analyses, a new shock-absorbing system is designed to protect commercial micromachined devices from unwanted high-g and high-frequency mechanical excitations. The new shock-absorbing system consists of close-packed microglasses within two metal enclosures and a viscoelastic layer fastened by steel bolts, which are biologically inspired from a spongy bone contained within a skull bone encompassed with the hyoid of a woodpecker. In the experimental characterizations using a 60 mm smoothbore air-gun, this bio-inspired shock-absorbing system shows a failure rate of 0.7% for the commercial micromachined devices at 60 000 g, whereas a conventional hard-resin method yields a failure rate of 26.4%, thus verifying remarkable improvement in the g-force tolerance of the commercial micromachined devices.
1
Bioinspiration & Biomimetics
27899097
10.1016/J.PBI.2004.05.008
27,899,097
Plant responses to bacterial quorum sensing signals.
Bacterial infection of plants often depends on the exchange of quorum sensing signals between nearby bacterial cells. It is now evident that plants, in turn, 'listen' to these bacterial signals and respond in sophisticated ways to the information. Plants also secrete compounds that mimic the bacterial signals and thereby confuse quorum sensing regulation in bacteria.
1
Current Opinion in Plant Biology
10008850
10.1073/PNAS.1012842108
10,008,850
Nanopatterned protein microrings from a diatom that direct silica morphogenesis
Diatoms are eukaryotic microalgae that produce species-specifically structured cell walls made of SiO2 (silica). Formation of the intricate silica structures of diatoms is regarded as a paradigm for biomolecule-controlled self-assembly of three-dimensional, nano- to microscale-patterned inorganic materials. Silica formation involves long-chain polyamines and phosphoproteins (silaffins and silacidins), which are readily soluble in water, and spontaneously form dynamic supramolecular assemblies that accelerate silica deposition and influence silica morphogenesis in vitro. However, synthesis of diatom-like silica structure in vitro has not yet been accomplished, indicating that additional components are required. Here we describe the discovery and intracellular location of six novel proteins (cingulins) that are integral components of a silica-forming organic matrix (microrings) in the diatom Thalassiosira pseudonana. The cingulin-containing microrings are specifically associated with girdle bands, which constitute a substantial part of diatom biosilica. Remarkably, the microrings exhibit protein-based nanopatterns that closely resemble characteristic features of the girdle band silica nanopatterns. Upon the addition of silicic acid the microrings become rapidly mineralized in vitro generating nanopatterned silica replicas of the microring structures. A silica-forming organic matrix with characteristic nanopatterns was also discovered in the diatom Coscinodiscus wailesii, which suggests that preassembled protein-based templates might be general components of the cellular machinery for silica morphogenesis in diatoms. These data provide fundamentally new insight into the molecular mechanisms of biological silica morphogenesis, and may lead to the development of self-assembled 3D mineral forming protein scaffolds with designed nanopatterns for a host of applications in nanotechnology.
1
Proceedings of the National Academy of Sciences of the United States of America
7365375
10.1242/JEB.051128
7,365,375
Non-wetting wings and legs of the cranefly aided by fine structures of the cuticle
Non-wetting surfaces are imperative to the survival of terrestrial and semi-aquatic insects as they afford resistance to wetting by rain and other liquid surfaces that insects may encounter. Thus, there is an evolutionary pay-off for these insects to adopt hydrophobic technologies, especially on contacting surfaces such as legs and wings. The cranefly is a weak flier, with many species typically found in wet/moist environments where they lay eggs. Water droplets placed on this insect's wings will spontaneously roll off the surface. In addition, the insect can stand on water bodies without its legs penetrating the water surface. The legs and wings of this insect possess thousands of tiny hairs with intricate surface topographies comprising a series of ridges running longitudinally along the long axis of the hair fibre. Here we demonstrate that this fine hair structure enhances the ability of the hairs to resist penetration into water bodies.
1
The Journal of Experimental Biology
7985977
10.1016/J.JTBI.2006.02.008
7,985,977
A finite element simulation scheme for biological muscular hydrostats.
An explicit finite element scheme is developed for biological muscular hydrostats such as squid tentacles, octopus arms and elephant trunks. The scheme is implemented by embedding muscle fibers in finite elements. In any given element, the fiber orientation can be assigned arbitrarily and multiple muscle directions can be simulated. The mechanical stress in each muscle fiber is the sum of active and passive parts. The active stress is taken to be a function of activation state, muscle fiber shortening velocity and fiber strain; while the passive stress depends only on the strain. This scheme is tested by simulating extension of a squid tentacle during prey capture; our numerical predictions are in close correspondence with existing experimental results. It is shown that the present finite element scheme can successfully simulate more complex behaviors such as torsion of a squid tentacle and the bending behavior of octopus arms or elephant trunks.
1
Journal of Theoretical Biology
18386848
10.1128/JB.188.1.202-210.2006
18,386,848
Reconstruction and Regulation of the Central Catabolic Pathway in the Thermophilic Propionate-Oxidizing Syntroph Pelotomaculum thermopropionicum
ABSTRACT Obligate anaerobic bacteria fermenting volatile fatty acids in syntrophic association with methanogenic archaea share the intermediate bottleneck step in organic-matter decomposition. These organisms (called syntrophs) are biologically significant in terms of their growth at the thermodynamic limit and are considered to be the ideal model to address bioenergetic concepts. We conducted genomic and proteomic analyses of the thermophilic propionate-oxidizing syntroph Pelotomaculum thermopropionicum to obtain the genetic basis for its central catabolic pathway. Draft sequencing and subsequent targeted gap closing identified all genes necessary for reconstructing its propionate-oxidizing pathway (i.e., methylmalonyl coenzyme A pathway). Characteristics of this pathway include the following. (i) The initial two steps are linked to later steps via transferases. (ii) Each of the last three steps can be catalyzed by two different types of enzymes. It was also revealed that many genes for the propionate-oxidizing pathway, except for those for propionate coenzyme A transferase and succinate dehydrogenase, were present in an operon-like cluster and accompanied by multiple promoter sequences and a putative gene for a transcriptional regulator. Proteomic analysis showed that enzymes in this pathway were up-regulated when grown on propionate; of these enzymes, regulation of fumarase was the most stringent. We discuss this tendency of expression regulation based on the genetic organization of the open reading frame cluster. Results suggest that fumarase is the central metabolic switch controlling the metabolic flow and energy conservation in this syntroph.
1
Journal of Bacteriology
96756716
10.1080/00218460902996952
96,756,716
Chemistry-Specific Interfacial Forces Between Barnacle (Semibalanus Balanoides) Cyprid Footprint Proteins and Chemically Functionalised AFM Tips
Cypris larvae of the barnacle Semibalanus balanoides leave proteinaceous footprints on surfaces during pre-settlement exploration. These footprints are considered to mediate temporary adhesion of cyprids to substrata and, as such, represent a crucial first step in the colonization of man-made surfaces by barnacles, a process known as biofouling. Interest in this system also stems from the potential for a synthetic reversible adhesion system, based on the strategy used by cyprids. Cyprid footprints were probed using atomic force microscopy (AFM) and nanomechanical data relating to interfacial adhesion forces were correlated with AFM tip chemistry. Commercial Si3N4-tips and chemically functionalized CH3-tips were chosen to mimic the interactions of cyprid footprints with hydrophilic and hydrophobic surfaces, respectively. Force-extension curves of protein bundles picked up by AFM tips exhibited a characteristic saw-tooth appearance for both types of tip, but demonstrated clear differences relating to pull-off force and pull-off length, based on tip chemistry. Additional (∼6 nN) interfacial adhesion forces between −CH3 functionalized tips and footprints were assigned to hydrophobic interactions. Footprint proteins adhered with greater tenacity to the hydrophobic tip. This may suggest conformational change and denaturing of the protein which would facilitate hydrophobic interaction by enhancing contact forces between −CH3 functionalized tips and hydrophobic groups in the footprint molecule(s). Neither tip removed proteins from the −NH2 substratum suggesting that specific chemical interactions, rather than simple wetting phenomena, govern the adhesion of footprint proteins to that surface.
1
Journal of Adhesion
17045607
10.1242/JEB.088450
17,045,607
Coordinated ventilation and spiracle activity produce unidirectional airflow in the hissing cockroach, Gromphadorhina portentosa
SUMMARY Insects exchange respiratory gases via an extensive network of tracheal vessels that open to the surface of the body through spiracular valves. Although gas exchange is known to increase with the opening of these spiracles, it is not clear how this event relates to gas flow through the tracheal system. We examined the relationship between respiratory airflow and spiracle activity in a ventilating insect, the hissing cockroach, Gromphadorhina portentosa, to better understand the complexity of insect respiratory function. Using simultaneous video recordings of multiple spiracular valves, we found that abdominal spiracles open and close in unison during periods of ventilation. Additionally, independent recordings of CO2 release from the abdominal and thoracic regions and observations of hyperoxic tracer gas movement indicate that air is drawn into the thoracic spiracles and expelled from the abdominal spiracles. Our video recordings suggest that this unidirectional flow is driven by abdominal contractions that occur when the abdominal spiracles open. The spiracles then close as the abdomen relaxes and fills with air from the thorax. Therefore, the respiratory system of the hissing cockroach functions as a unidirectional pump through the coordinated action of the spiracles and abdominal musculature. This mechanism may be employed by a broad diversity of large insects that respire by active ventilation.
1
The Journal of Experimental Biology
16608886
10.1002/MABI.200800252
16,608,886
A water-borne adhesive modeled after the sandcastle glue of P. californica.
Polyacrylate glue protein analogs of the glue secreted by Phragmatopoma californica, a marine polycheate, were synthesized with phosphate, primary amine, and catechol sidechains with molar ratios similar to the natural glue proteins. Aqueous mixtures of the mimetic polyelectrolytes condensed into liquid complex coacervates around neutral pH. Wet cortical bone specimens bonded with the coacervates, oxidatively crosslinked through catechol sidechains, had bond strengths nearly 40% of the strength of a commercial cyanoacrylate. The unique material properties of complex coacervates may be ideal for development of clinically useful adhesives and other biomaterials.
1
Macromolecular Bioscience
15124800
10.1016/S0960-9822(99)80189-4
15,124,800
Convergence of specialised behaviour, eye movements and visual optics in the sandlance (Teleostei) and the chameleon (Reptilia)
Chameleons have a number of unusual, highly specialised visual features, including telescopic visual optics with a reduced lens power, wide separation of the eye's nodal point from the axis of rotation, a deep-pit fovea, rapid pre-calculated strikes for prey based on monocular depth judgements (including focus), and a complex pattern of partially independent alternating eye movements. The same set of features has been acquired independently by a teleost, the sandlance Limnichthyes fasciatus. Despite its underwater lifestyle, this fish displays visual behaviour and rapid strikes for prey that are remarkably similar to those of the chameleon [1]. In a direct comparison of the two species, we have revealed other, previously unsuspected, similarities, such as corneal accommodation, which was unknown in teleosts, as well as bringing together, for the first time, data collected from both species. The sandlance is the only teleost, among thousands studied, that has corneal refraction, corneal accommodation and reduced lens power, as well as sharing the other specialised optical features seen in chameleons. The independent eye movement pattern in the sandlance is also unusual and similar to that of the chameleon. The selection pressures that have produced this remarkable example of convergence may relate to common visual constraints in the life styles of these two phylogenetically disparate species.
1
Current Biology
25887907
10.1146/ANNUREV.BIOPHYS.37.032807.125804
25,887,907
Biophysics of catch bonds.
Receptor-ligand bonds strengthened by tensile mechanical force are referred to as catch bonds. This review examines experimental data and biophysical theory to analyze why mechanical force prolongs the lifetime of these bonds rather than shortens the lifetime by pulling the ligand out of the binding pocket. Although many mathematical models can explain catch bonds, experiments using structural variants have been more helpful in determining how catch bonds work. The underlying mechanism has been worked out so far only for the bacterial adhesive protein FimH. This protein forms catch bonds because it is allosterically activated when mechanical force pulls an inhibitory domain away from the ligand-binding domain. Other catch bond-forming proteins, including blood cell adhesion proteins called selectins and the motor protein myosin, show evidence of allosteric regulation between two domains, but it remains unclear if this is related to their catch bond behavior.
1
Annual Review of Biophysics
15863485
10.1021/NP900630W
15,863,485
Butenolides from plant-derived smoke: natural plant-growth regulators with antagonistic actions on seed germination.
Smoke plays an intriguing role in promoting the germination of seeds of many species following a fire. Recently, a bicyclic compound containing a condensed butenolide moiety, 3-methyl-2H-furo[2,3-c]pyran-2-one (1), was reported as a potent germination promoter from plant-derived smoke. In this study, a related butenolide, 3,4,5-trimethylfuran-2(5H)-one (2), which inhibits germination and significantly reduces the effect of 1 when applied simultaneously, was also isolated from plant-derived smoke. The interaction of these compounds with opposing actions on seed germination may have important ecological implications in a post-fire environment and could be useful molecules for understanding the events involved in breaking seed dormancy and promoting seed germination.
1
Journal of Natural Products
26686967
10.1152/AJPLEGACY.1973.224.4.848
26,686,967
Temperature regulation and heat balance in running cheetahs: a strategy for sprinters?
null
1
American Journal of Physiology
302680
10.1073/PNAS.0910778107
302,680
Ballistic tongue projection in chameleons maintains high performance at low temperature
Environmental temperature impacts the physical activity and ecology of ectothermic animals through its effects on muscle contractile physiology. Sprinting, swimming, and jumping performance of ectotherms decreases by at least 33% over a 10 °C drop, accompanied by a similar decline in muscle power. We propose that ballistic movements that are powered by recoil of elastic tissues are less thermally dependent than movements that rely on direct muscular power. We found that an elastically powered movement, ballistic tongue projection in chameleons, maintains high performance over a 20 °C range. Peak velocity and power decline by only 10%–19% with a 10 °C drop, compared to >42% for nonelastic, muscle-powered tongue retraction. These results indicate that the elastic recoil mechanism circumvents the constraints that low temperature imposes on muscle rate properties and thereby reduces the thermal dependence of tongue projection. We propose that organisms that use elastic recoil mechanisms for ecologically important movements such as feeding and locomotion may benefit from an expanded thermal niche.
1
Proceedings of the National Academy of Sciences of the United States of America
216222872
10.1093/BIOLINNEAN/BLAA027
216,222,872
Stability in fig tree–fig wasp mutualisms: how to be a cooperative fig wasp
null
1
Biological Journal of The Linnean Society
85670448
10.1093/FORESTRY/72.4.337
85,670,448
Should the wind disturbance patterns observed in natural forests be mimicked in planted forests in the British uplands
Summary Recent developments in UK forestry policy require the adoption of management practices that maintain and improve the biodiversity of managed forests. One approach is to use natural disturbance in unmanaged forests as a template for setting the scale, frequency and pattern of forest operations in managed forests. This review considers the relevance of this approach for conifer plantations in upland Britain. The dynamics of British planted forests are compared with the disturbance dynamics of analogous natural forests with particular reference to disturbance by strong winds. Western hemlock‐Sitka spruce (Tsuga heterophylla‐Picea sitchensis) forests in the Pacific North-west of North America and particularly South-east Alaska provide the most promising comparison. There are few reports on disturbance in these forests, but the regime includes both gap-phase and stand replacement dynamics due to wind. However, the landscape proportion and pattern of resulting structural types are not well defined. The dynamics of planted forests in Britain are dominated by rotational patch clearfelling which results in regular stand replacement and little possibility of the stands developing beyond the stage of stem exclusion towards old-growth. The pattern and timing of felling is driven by economic and visual amenity considerations rather than by an attempt to mimic natural disturbance patterns. Moreover, the structural complexity and remnant elements (such as deadwood, large trees, vegetation patches) left after large scale disturbance are rarely found after conventional timber harvesting. The authors conclude that natural wind disturbance regimes have potential as a reference point for management in British upland forests but at present are not relevant as a model to mimic explicitly. This is because the biodiversity benefits of adopting a ‘natural’ approach in planted forests are unclear compared with management guided by other criteria such as rarity. Furthermore, the spatial and temporal pattern to be mimicked is not sufficiently well understood. Improved knowledge could inform decisions on the scale and distribution of harvesting across a landscape, and modify silvicultural operations to create and maintain the structures and patterns associated with natural disturbance. However, further research is needed to quantify the spatial and temporal characteristics of wind disturbance in upland forests in Britain and in natural forests elsewhere.
1
Forestry
85577019
10.1006/ANBO.1993.1089
85,577,019
The Mechanics of the Flower Stem of the Sedge Carex acutiformis
The mechanics of the triangular stems of Carex acutiformis was investigated by subjecting sections to bending and torsional tests. The stem was rigid in bending, being stiffened peripherally by lignified material around the vascular bundles, but because of its triangular shape it was vulnerable to local buckling. Despite being and narrow the stem was able to support the seed head, though it sagged appreciably towards the tip. In contrast the stem had very low torsional rigidity, both because of its triangular shape because the strands of lignified material were isolated from each other. In its lowland habitat this allows the drooping stem to twist away from the light winds, so reducing drag and the chances of self-fertilization. This method of reconfiguring is not possible in the shorter, stiffer mountain sedges which must withstand higher winds; many therefore have more circular stems which will be more efficient at resisting bending.
1
Annals of Botany
10264641
10.1002/CHEM.19950010705
10,264,641
Biologically Induced Reduction in Symmetry: A Study of Crystal Texture of Calcitic Sponge Spicules
Organisms can exert a remark- able degree of control over crystal growth. One way of achieving this is by the ad- sorption of specialized macromolecules on specific planes of the growing crystals. With continued growth of the crystal, the macromolecules are incorporated inside the crystal bulk. Their presence does not change the crystal structure, but creates discontinuities in the perfect lattice. Here we study in detail three unusual cases of reduction in symmetry at the level of crys- tal domain shapes, induced by this con- trolled intercalation. We examined sponge spicules, which are single crystals of Mg- bearing calcite. They were specifically chosen for this study, because their mor- phologies do not reflect the hexagonal symmetry of calcite. Their crystal textures (coherence lengths and angular spreads) were characterized by high-resolution X- ray diffraction with well-collimated syn- chrotron radiation. The results are com- pared to analogous studies of synthetic calcite and Mg-bearing calcite. In all the selected spicules reduction in symmetry is observed in the coherence lengths among symmetry-related crystallographic direc- tions. The reconstructed shapes of the do- mains of perfect structure closely match the specific spicule morphologies. The synthetic crystals show no such reduction in symmetry. Although the manner by which such exquisite control is achieved is not known, we envisage it involving a combination of oriented nucleation with either physical or stereochemically driven adsorption.
1
Chemistry: A European Journal
20278427
10.1116/1.2751405
20,278,427
Impact of engineered surface microtopography on biofilm formation of Staphylococcus aureus
The surface of an indwelling medical device can be colonized by human pathogens that can form biofilms and cause infections. In most cases, these biofilms are resistant to antimicrobial therapy and eventually necessitate removal or replacement of the device. An engineered surface microtopography based on the skin of sharks, Sharklet AFTM, has been designed on a poly(dimethyl siloxane) elastomer (PDMSe) to disrupt the formation of bacterial biofilms without the use of bactericidal agents. The Sharklet AFTM PDMSe was tested against smooth PDMSe for biofilm formation of Staphylococcus aureus over the course of 21 days. The smooth surface exhibited early-stage biofilm colonies at 7 days and mature biofilms at 14 days, while the topographical surface did not show evidence of early biofilm colonization until day 21. At 14 days, the mean value of percent area coverage of S. aureus on the smooth surface was 54% compared to 7% for the Sharklet AFTM surface (p<0.01). These results suggest that surface modification of indwelling medical devices and exposed sterile surfaces with the Sharklet AFTM engineered topography may be an effective solution in disrupting biofilm formation of S. aureus.
1
Biointerphases
14217413
10.1111/J.1365-2435.2008.01523.X
14,217,413
Nutritional toxicology of mammals: regulated intake of plant secondary compounds
Summary 1. Many mammalian herbivores continually face the possibility of being poisoned by the natural toxins in the plants they consume. A recent key discovery in this area is that mammalian herbivores are capable of regulating the dose of plant secondary compounds (PSCs) ingested. 2. The ‘regulation model’ describes the factors driving ingestion of PSCs by mammals and can be dissected into two separate hypotheses related to meal size and inter-meal interval (IMI). Testing these hypotheses independently yields a more thorough understanding of the underlying and potentially interconnected mechanisms. 3. Three mechanisms could influence the size of meals that contain PSCs. These are the plasma concentration of PSCs, conditioned learning, and activation of bitter receptors in the intestine. 4. Two mechanisms are proposed to govern the IMI. The first predicts that IMI is dependent on the concentration of PSC metabolites in the plasma; feeding will not resume until metabolite concentrations are acceptable for further ingestion of PSCs. The second hypothesis proposes that the intestinal bitter receptors modulate IMI through release of satiety compounds.
1
Functional Ecology
5066384
10.1007/S00425-002-0878-2
5,066,384
Rapid increase of vacuolar volume in response to salt stress
Abstract. Suspension-cultured cells of mangrove [Bruguiera sexangula (Lour.) Poir.] showed a rapid increase in vacuolar volume under salt stress, although there was no change in the cell volume. The rapid increase in the vacuolar volume was an active process, which followed the activation of the tonoplast H+-ATPase and the vacuolar acid phosphatase. The same phenomenon was observed in barley (Hordeum vulgare L. cv. Doriru) root meristematic cells under salt stress but not in pea (Pisum sativum L.). Increases in vacuolar volume could potentially protect the cytoplasm by decreasing the cytoplasmic volume during the initial phases of salt stress.
1
Planta
8337095
10.1126/SCIENCE.1155495
8,337,095
Environmental Genomics Reveals a Single-Species Ecosystem Deep Within Earth
DNA from low-biodiversity fracture water collected at 2.8-kilometer depth in a South African gold mine was sequenced and assembled into a single, complete genome. This bacterium, Candidatus Desulforudis audaxviator, composes >99.9% of the microorganisms inhabiting the fluid phase of this particular fracture. Its genome indicates a motile, sporulating, sulfate-reducing, chemoautotrophic thermophile that can fix its own nitrogen and carbon by using machinery shared with archaea. Candidatus Desulforudis audaxviator is capable of an independent life-style well suited to long-term isolation from the photosphere deep within Earth's crust and offers an example of a natural ecosystem that appears to have its biological component entirely encoded within a single genome.
1
Science
337000
10.1098/RSPB.2011.0069
337,000
Trabecular bone scales allometrically in mammals and birds
Many bones are supported internally by a latticework of trabeculae. Scaling of whole bone length and diameter has been extensively investigated, but scaling of the trabecular network is not well characterized. We analysed trabecular geometry in the femora of 90 terrestrial mammalian and avian species with body masses ranging from 3 g to 3400 kg. We found that bone volume fraction does not scale substantially with animal size, while trabeculae in larger animals' femora are thicker, further apart and fewer per unit volume than in smaller animals. Finite element modelling indicates that trabecular scaling does not alter the bulk stiffness of trabecular bone, but does alter strain within trabeculae under equal applied loads. Allometry of bone's trabecular tissue may contribute to the skeleton's ability to withstand load, without incurring the physiological or mechanical costs of increasing bone mass.
1
Proceedings of The Royal Society B: Biological Sciences
214789022
10.1016/J.BEPROC.2020.104118
214,789,022
Evaluating the social networks of four flocks of captive flamingos over a five-year period: Temporal, environmental, group and health influences on assortment
Flamingos are well known for their gregarious habits and aggregations in large flocks, but evaluation of the mechanisms behind social grouping remain poorly understood. Captive birds provide a useful model for investigating aspects of social choice in highly gregarious, long-lived species. Animals invest in social relationships that convey fitness benefits and bonds can be long-lasting. For some species, field-based measurement of social networks can be difficult. Captive populations therefore provide a useful alternative for measuring social choices. Data were collected on flamingos at WWT Slimbridge Wetland Centre from 2013 to 2016 and compared to data from 2012. For three flocks, associations were analysed along with individual foot health scores to identify any relationship between health and social behaviour. Long-term partnerships were present in all flocks; preferred associates noted in 2012 were present in 2016. Matrix correlations across years were positive; arrangements of dyads, trios and quartets with higher ties strengths were visible at the beginning and end of the study. Both male-male and female-female bonds were stable over time. All flamingos were more frequently seen socialising than solitary; those in the largest flock showed the highest occurrence of social behaviour (irrespective of enclosure size differences). The number of connections realised from all available within a network was significantly influenced by season. Foot health did not predict associations in these three flamingo networks. Our results indicate that flamingo societies are complex (i.e. formed of long-standing preferential partnerships and not loose, random connections) and the impact of flock size and environment on sociality should be investigated further. These results are helpful for those working with captive flamingos to consider the number of birds housed so that an array of opportunities for choice of associate and/or breeding partner are available in zoo-housed flocks.
1
Behavioural Processes
26736062
10.3354/MEPS318153
26,736,062
Chemically mediated antifouling in the red alga Delisea pulchra
Using laboratory assays, we tested whether the secondary metabolites (furanones) on the surface of the red alga Delisea pulchra deter the settlement and growth of a range of ecologically relevant fouling organisms. D. pulchra and 4 other co-occurring seaweeds were almost exclusively fouled by other algae. Consequently, we carried out laboratory assays using propagules from 4 fouling algae (Ulva sp., Ceramium sp., Polysiphonia sp. and Ectocarpus siliculosis) representing the natural fouling community. The crude surface extract of D. pulchra at the same concentration as on the surface of the plant, the furanone fraction of this extract, and pure furnaones, deterred the settlement of fouling organisms in ecologically relevant assays. These data, coupled with knowledge of the surface concentration of furanones on D. pulchra and a mechanism by which furanones are sequestered onto the surface of the plant, provide a rigorous demonstration of chemically mediated antifouling.
1
Marine Ecology Progress Series
59468561
10.3354/AME015153
59,468,561
Barotolerance of fungi isolated from deep-sea sediments of the Indian Ocean
Two species of filamentous fungi, AspergiUus ustus (Bain.) Thom & Church and Graphium sp., were isolated from calcareous animal shells at depths of 860 m in the Arabian Sea and 965 m in the Bay of Bengal. Laboratory experiments showed germination of conidia, growth of hyphae and microconidiation in both the fungi at 100 bar pressure at 10 and 30°C suggesting barotolerance The fungi also secreted barotolerant protease under these conditions. Protease synthesised and secreted in cultures grown at 1 bar was also active under 100 bar pressure at 10 and 30°C. At 1O0C, the fungi showed better conidial germination, growth and protease secretion when subjected to 100 bar than when grown at 1 atmosphere. The results indicate barotolerance of terrestrial species of fungl and suggest that they might be active under deep-sea conditions.
1
Aquatic Microbial Ecology
32262885
10.1073/PNAS.0601705103
32,262,885
Adhesion of single bacterial cells in the micronewton range.
The adhesion of bacteria to surfaces plays critical roles in the environment, disease, and industry. In aquatic environments, Caulobacter crescentus is one of the first colonizers of submerged surfaces. Using a micromanipulation technique, we measured the adhesion force of single C. crescentus cells attached to borosilicate substrates through their adhesive holdfast. The detachment forces measured for 14 cells ranged over 0.11 to 2.26 microN, averaging 0.59 +/- 0.62 microN. Based on the calculation of stress distribution with the finite element analysis method (dividing an object into small grids and calculating relevant parameters for all of the elements), the adhesion strength between the holdfast and the substrate is >68 N/mm(2) in the central region of contact. To our knowledge, this strength of adhesion is the strongest ever measured for biological adhesives.
1
Proceedings of the National Academy of Sciences of the United States of America
41764382
10.1073/PNAS.1014280108
41,764,382
Shape of tropoelastin, the highly extensible protein that controls human tissue elasticity
Elastin enables the reversible deformation of elastic tissues and can withstand decades of repetitive forces. Tropoelastin is the soluble precursor to elastin, the main elastic protein found in mammals. Little is known of the shape and mechanism of assembly of tropoelastin as its unique composition and propensity to self-associate has hampered structural studies. In this study, we solve the nanostructure of full-length and corresponding overlapping fragments of tropoelastin using small angle X-ray and neutron scattering, allowing us to identify discrete regions of the molecule. Tropoelastin is an asymmetric coil, with a protruding foot that encompasses the C-terminal cell interaction motif. We show that individual tropoelastin molecules are highly extensible yet elastic without hysteresis to perform as highly efficient molecular nanosprings. Our findings shed light on how biology uses this single protein to build durable elastic structures that allow for cell attachment to an appended foot. We present a unique model for head-to-tail assembly which allows for the propagation of the molecule’s asymmetric coil through a stacked spring design.
1
Proceedings of the National Academy of Sciences of the United States of America
1320885
10.1242/JEB.051276
1,320,885
The protective role of aquaporins in the freeze-tolerant insect Eurosta solidaginis: functional characterization and tissue abundance of EsAQP1
SUMMARY The movement of water and small solutes is integral to the survival of freezing and desiccation in insects, yet the underlying mechanisms of these processes are not fully known. Recent evidence suggests that aquaporin (AQP) water channels play critical roles in protecting cells from osmotic damage during freezing and desiccation. Our study sequenced, functionally characterized and measured the tissue abundance of an AQP from freeze-tolerant larvae of the gall fly, Eurosta solidaginis (Diptera: Tephritidae). The newly characterized EsAQP1 contains two NPA motifs and six transmembrane regions, and is phylogenetically related to an AQP from the anhydrobiotic chironomid Polypedilum vanderplanki. Using a Xenopus laevis oocyte swelling assay, we demonstrated that EsAQP1 increases water permeability to nine times that of simple diffusion through the membrane. In contrast to its high water permeability, EsAQP1 was impermeable to both glycerol and urea. The abundance of EsAQP1 increased from October to December in all tissues tested and was most abundant in the brain of winter larvae. Because the nervous system is thought to be the primary site of freezing injury, EsAQP1 may cryoprotect the brain from damage associated with water imbalance. The sequence, phylogenetic relationship, osmotic permeability, tissue distribution and seasonal abundance of EsAQP1 further support the role of AQPs in promoting freezing tolerance.
1
The Journal of Experimental Biology