bluuebunny/crossref_metadata_2025_split huggingface dataset:
The scaling of acceleratory aquatic locomotion: body size and tail-flip performance of the california spiny lobster panulirus interruptus
Authors: Nauen Jennifer C. , Shadwick Robert E. 
Published: April 2021

ABSTRACT
Tail-flipping is a crucial escape locomotion of crustaceans which has been predicted to be limited by increased body mass (Mb). Given isometric growth, one may predict that with growth event duration will decrease as Mb−1/3, translational distances will increase as Mb1/3, translational velocity will be independent of Mb, translational acceleration will decrease as Mb−1/3, angular displacement will be independent of Mb and angular velocity and angular acceleration will decrease as Mb−1/3. We tested these hypotheses by examining the scaling of 12 morphological variables, five kinematic variables and six performance variables of tail-flipping by the California spiny lobster Panulirus interruptus.
Growth approximated isometry, which validated the use of the proposed scaling hypotheses. For animals from 1 to 1000 g Mb, the predicted scaling relationships for tail-flip duration and translational distance and velocity variables were supported; however, translational acceleration performance was much better than predicted. Predictions for rotation and rotational velocity variables were not supported, while the rotational acceleration data closely matched the predicted relationship.
The increase in tail-flip duration as predicted suggests that muscle shortening velocity decreases with growth; the sustained acceleration performance (similar to findings for shrimp and fish fast-starts) suggests that muscle force output may increase at a greater rate than predicted by isometry. The scaling of rotational acceleration indicates that the torque produced during the tail-flip scales with a mass exponent greater than 1. Comparison of the tail-flip performance of Panulirus interruptus with those of other crustacean species reveals a wide range in performance by animals of similar body size, which suggests that the abdominal muscle may show interesting differences in contractile properties among different species.
Cardiorespiratory response to progressive hypoxia and hypercapnia in the turtle trachemys scripta
Authors: Herman Jay K. , Smatresk Neal J. 
Published: April 2021

ABSTRACT
The ventilatory responses of chelonian reptiles to hypoxic and hypercapnic stress have been fairly well described. As turtles are capable of large cardiac shunts, changes in pulmonary perfusion may be an equally viable and potent response to these stressors. To test this hypothesis, conscious unrestrained turtles were unidirectionally ventilated while blood flow in the left pulmonary artery (Q̇LPA) and left aortic arch (Q̇LAo) was monitored. Turtles were exposed to step changes (2.5 h step−1) in O2 tension (30, 15, 5, 2.5 or 0 % O2; CO2 inflow maintained constant) on day 1 followed by step changes in CO2 tension (0, 2, 4, 8 % CO2; O2 inflow maintained constant) on day 2. Steady-state cardiorespiratory variables were recorded for the last 30 min of each step change in gas tension.
Progressive hypoxia resulted in progressive increases in ventilation, Q̇LPA and Q̇LAo and a small, but non-significant, increase in heart rate. Progressive hypercapnia resulted in a progressive increase in ventilation, while Q̇LPA and Q̇Lao did not change at any level of CO2. These results suggest that information from the O2-sensitive chemoreceptors appears to be stimulatory to both the cardiovascular and ventilatory control systems, while CO2 chemoreception appears to affect primarily the ventilatory control system. These results also suggest that, in animals capable of intracardiac shunting, increasing pulmonary perfusion may be an integral component of the reflex response to hypoxia.
Contractile properties of muscles used in sound production and locomotion in two species of gray tree frog
Authors: Marsh Richard L. 
Published: April 2021

ABSTRACT
The sound-producing muscles of frogs and toads are interesting because they have been selected to produce high-power outputs at high frequencies. The two North American species of gray tree frog, Hyla chrysoscelis and Hyla versicolor, are a diploid–tetraploid species pair. They are morphologically identical, but differ in the structure of their advertisement calls. H. chrysoscelis produces very loud pulsed calls by contracting its calling muscles at approximately 40 Hz at 20 °C, whereas, H. versicolor operates the homologous muscles at approximately 20 Hz at this temperature. This study examined the matching of the intrinsic contractile properties of the calling muscles to their frequency of use. I measured the isotonic and isometric contractile properties of two calling muscles, the laryngeal dilator, which presumably has a role in modulating call structure, and the external oblique, which is one of the muscles that provides the mechanical power for calling. I also examined the properties of the sartorius as a representative locomotor muscle. The calling muscles differ greatly in twitch kinetics between the two species. The calling muscles of H. chrysoscelis reach peak tension in a twitch after approximately 15 ms, compared with 25 ms for the same muscles in H. versicolor. The muscles also differ significantly in isotonic properties in the direction predicted from their calling frequencies. However, the maximum shortening velocities of the calling muscles of H. versicolor are only slightly lower than those of the comparable muscles of H. chrysoscelis. The calling muscles have similar maximum shortening velocities to the sartorius, but have much flatter force–velocity curves, which may be an adaptation to their role in cyclical power output. I conclude that twitch properties have been modified more by selection than have intrinsic shortening velocities. This difference corresponds to the differing roles of shortening velocity and twitch kinetics in determining power output at differing frequencies.
Power output of sound-producing muscles in the tree frogs Hyla versicolor and Hyla chrysoscelis
Authors: Girgenrath Mahasweta , Marsh Richard L. 
Published: April 2021

ABSTRACT
Sound-producing muscles provide the opportunity of studying the limits of power production at high contractile frequencies. We used the work loop technique to determine the power available from the external oblique muscles in two related species of North American gray tree frog, Hyla chrysoscelis and Hyla versicolor. These trunk muscles contract cyclically, powering high-intensity sound production in anuran amphibians. The external oblique muscles in H. chrysoscelis have an in vivo operating frequency of 40–55 Hz at 20–25 °C, whereas in H. versicolor these muscles contract with a frequency of 20–25 Hz at these temperatures. In vivo investigations have shown that these muscles use an asymmetrical sawtooth length trajectory (with a longer shortening phase compared with the lengthening phase) during natural cycles. To study the influence of this particular length trajectory on power output, we subjected the muscles to both sinusoidal and sawtooth length trajectories. In both species, the sawtooth trajectory yielded a significantly higher power output than the sinusoidal length pattern. The maximum power output during sawtooth cycles was similar in both species (54W kg−1 in H. chrysoscelis and 58 W kg−1 in H. versicolor). These values are impressive, particularly at the operating frequencies and temperatures of the muscle. The sinusoidal length trajectory yielded only 60 % of the total power output compared with the sawtooth trajectory (34W kg−1 for H. chrysoscelis and 36 W kg−1 for H. versicolor). The optimum cycle frequencies maximizing the power output using a sawtooth length pattern were approximately 44 Hz for H. chrysoscelis and 21 Hz for H. versicolor. These frequencies are close to those used by the two species during calling. Operating at higher frequencies, H. chrysoscelis maximized power at a strain amplitude of only 8 % compared with a value of 12 % in H. versicolor. These strains match those used in vivo during calling. The stimulus timing observed in vivo during calling was also similar to that yielding maximum power at optimal frequency in both species (6 ms and 8 ms before the start of shortening in H. chrysoscelis and H. versicolor, respectively). As expected, twitch duration in H. chrysoscelis is much shorter than that in H. versicolor (23 ms and 37 ms, respectively). There was a less remarkable difference between their maximum shortening velocities (Vmax) of 13.6 L0 s−1 in H. chrysoscelis and 11.1 L0 s−1 in H. versicolor, where L0 is muscle length. The force–velocity curves are very flat, which increases power output. At the myofibrillar level, the flat force–velocity curves more than compensate for the lower peak isometric force found in these muscles. The data presented here emphasize the importance of incorporating in vivo variables in designing in vitro studies.
From cellulose to cell
Authors: Vincent Julian F. V. 
Published: April 2021

ABSTRACT
The cell wall is often pictured as a more-or-less random feltwork of cellulose microfibrils in association with other polysaccharide and protein complexes. There is evidence from morphology, morphogenesis and mechanics that the structures in the cell wall are far more regular and that their interactions are driven by their chemical and morphological properties. In particular, a model based on liquid crystal structures has more than morphological implications.
Mechanical behaviour of plant tissues: composite materials or structures?
Authors: Spatz H.-Ch. , Köhler L. , Niklas K. J. 
Published: April 2021

ABSTRACT
The mechanical characteristics of the strengthening tissue of young axes of Aristolochia macrophylla were studied in successive loading–unloading cycles in tension. Elastic, viscoelastic and plastic deformations could be distinguished. After the first cycle, the material was in a state different from its original state, to which it returned only partially and/or slowly. Internal ‘microstructural’ prestresses are considered as an explanation for the mechanical behaviour seen in Aristolochia macrophylla and several other plants.
The aerodynamics and hydrodynamics of plants
Authors: Ennos A. R. 
Published: April 2021

ABSTRACT
Because they grow away from their substratum to compete for light, plants have to withstand hydrodynamic or aerodynamic drag. Both water and land plants reconfigure in response to this drag, and this is presumed to reduce the risk of mechanical failure. However, there is little unequivocal evidence of drag reduction in large trees as a result of reconfiguration. Land plants must also transport water internally to their tissues, and many have developed xylem tracheids and vessels that help speed up this process. Recent evidence that tree height is limited by water supply suggests that water transport efficiency must be a crucial element in tree design. However, the resistance of many parts of the xylem is still unknown. More focused work is urgently required to shed light on the evolution and ecology of plants in relation to the flow of fluids.
The design of mineralised hard tissues for their mechanical functions
Authors: Currey John D. 
Published: April 2021

ABSTRACT
Most hard tissues have as their primary purpose to be stiff. Outside the arthropods, mineralisation of a soft organic matrix is the almost universal method of producing high stiffness. However, stiffening brings with it the undesirable mechanical result of brittleness (lack of toughness). The mineralisation of some tissues, such as bone and dentine, can be modified rather easily, in evolutionary terms, to produce the optimum mix of stiffness with bending strength (which, except at the highest mineralisations, go together) on one hand and toughness on the other hand. However, in most other tissues, such as mollusc shell, echinoderm skeleton, brachiopod shell, barnacle shell and enamel, mineralisation is almost all-or-none, and no subtle gradations seem possible. In such cases, other features, such as architecture, must be modified to produce a useful skeleton.
Not only the mechanical properties of the skeletal tissue, but its cost, mass and time taken for production will, biologists tend to assume, be balanced by natural selection to produce a satisfactory result. However, such complexity makes it difficult to be sure that we understand the extent to which mineralised skeletal materials are the best possible solution to the problems facing the animals and that we are not just telling ‘Just-So’ stories. Furthermore, there are some skeletal materials that do not seem to make much sense at the moment, although no doubt all will become clear eventually.
The mechanical design of spider silks: from fibroin sequence to mechanical function
Authors: Gosline J. M. , Guerette P. A. , Ortlepp C. S. , Savage K. N. 
Published: April 2021

ABSTRACT
Spiders produce a variety of silks, and the cloning of genes for silk fibroins reveals a clear link between protein sequence and structure–property relationships. The fibroins produced in the spider’s major ampullate (MA) gland, which forms the dragline and web frame, contain multiple repeats of motifs that include an 8–10 residue long poly-alanine block and a 24–35 residue long glycine-rich block. When fibroins are spun into fibres, the poly-alanine blocks form β-sheet crystals that crosslink the fibroins into a polymer network with great stiffness, strength and toughness. As illustrated by a comparison of MA silks from Araneus diadematus and Nephila clavipes, variation in fibroin sequence and properties between spider species provides the opportunity to investigate the design of these remarkable biomaterials.
The design of soft collagenous load-bearing tissues
Authors: Ker Robert F. 
Published: April 2021

ABSTRACT
Tendon, articular cartilage and the human heel pad are all soft load-bearing collagenous tissues but are designed according to utterly different micromechanical principles. Tendon is (probably) a fibre-reinforced composite material. The mechanical properties of cartilage depend on osmotic pressure developed within an aqueous proteoglycan gel and resisted by tension in a collagenous network. The micromechanics of the heel pad have not previously been described quantitatively. Order-of-magnitude calculations are introduced to assess a model based on a fluid-filled cushion. The processes of biological design are illustrated by considering tendon. Structural design determines the tendon’s cross-sectional area relative to that of its muscle and, hence, the maximum stress to which the tendon may be subjected in life. Stress-in-life varies widely between tendons. Material design includes the development of compressive stiffness in the regions where transverse loads arise. More generally, the fatigue quality of each tendon is adjusted to suit its stress-in-life. The correlation between fatigue quality and stress-in-life means that every tendon is subject, on average, to a comparable rate of fatigue damage. Homeostasis requires that routine repair can keep up with this rate of damage.
Dynamics of muscle function during locomotion: accommodating variable conditions
Authors: Biewener Andrew A. , Gillis Gary B. 
Published: April 2021

ABSTRACT
Much of what we know about animal locomotion is derived from studies examining animals moving within a single, homogeneous environment, at a steady speed and along a flat grade. As a result, the issue of how musculoskeletal function might shift to accommodate variability within the external environment has remained relatively unexplored. One possibility is that locomotor muscles are differentially recruited depending upon the environment in which the animal is moving. A second possibility is that the same muscles are recruited, but that they are activated in a different manner so that their contractile function differs according to environment. Finally, it is also possible that, in some cases, animals may not need to alter their musculoskeletal function to move under different external conditions. In this case, however, the mechanical behavior appropriate for one environmental condition may constrain locomotor performance in another. To begin to explore the means by which animals accommodate variable conditions in their environment, we present three case studies examining how musculoskeletal systems function to allow locomotion under variable conditions: (1) eels undulating through water and across land, (2) turkeys running on level and inclined surfaces, and (3) ducks using their limbs to walk and to paddle. In all three of these examples, the mechanical behavior of some muscle(s) involved in locomotion are altered, although to different degrees and in different ways. In the running turkeys, the mechanical function of a major ankle extensor muscle shifts from contracting isometrically on a flat surface (producing little work and power), to shortening actively during contraction on an uphill gradient (increasing the amount of work and power generated). In the ducks, the major ankle extensor undergoes the same general pattern of activation and shortening in water and on land, except that the absolute levels of muscle stress and strain and work output are greater during terrestrial locomotion. In eels, a transition to land elicits changes in electromyographic duty cycles and the relative timing of muscle activation, suggesting some alteration in the functional mechanics of the underlying musculature. Only by studying muscle function in animals moving under more variable conditions can we begin to characterize the functional breadth of the vertebrate musculoskeletal system and understand more fully its evolutionary design.
Animal movement, mechanical tuning and coupled systems
Authors: Daniel Thomas L. , Tu Michael S. 
Published: April 2021

ABSTRACT
Over the past two decades, there has been a growing interest in developing predictive models of animal movement and force generation in fluids. In a departure from past studies that have asked how prescribed motions of a propulsor (wing or fin) generate lift and thrust during swimming and flying, we are increasingly interested in predicting the propulsor’s movement as well as the forces generated by it. This interest, motivated by a need to understand the control and dynamics of locomotion and its applications to robotics and animal physiology, requires that we develop integrative models and analyses of swimming and flying that incorporate neural control and muscle physiology into more traditional biomechanical studies of locomotion in fluids. This approach extends from whole-animal studies to the molecular basis of force generation. In this paper, we explore mechanical tuning from the level of the whole animal to the proteins driving force generation in muscle.
Are there mechanical limits to size in wave-swept organisms?
Authors: Denny Mark 
Published: April 2021

ABSTRACT
Hydrodynamic forces imposed by ocean waves are thought to limit the size of nearshore plants and animals, but it has proved difficult to determine the mechanism. Explanations based on the scaling mismatch between hydrodynamic accelerational forces and the strength of organisms do not work. Mechanisms that incorporate the allometry of drag and strength accurately predict the maximal size of intertidal algae but not of animals, and internally imposed inertial forces may explain the limits to size in large kelps. The general question of size in wave-swept organisms remains open and intriguing.
Ecological biomechanics of benthic organisms: life history, mechanical design and temporal patterns of mechanical stress
Authors: Koehl M. A. R. 
Published: April 2021

ABSTRACT
We can gain biomechanical insights if we couple knowledge of the environments, ecological roles and life history strategies of organisms with our laboratory analyses of their mechanical function or fluid dynamics, as illustrated by studies of the mechanical design of bottom-dwelling marine organisms. Obviously, measurements of the spatial and temporal distribution of loads on an organism in nature reveal the magnitudes and rates at which biomechanical tests should be performed in the laboratory. Furthermore, knowledge of the population biology and ecological interactions of the organisms being studied is crucial to determine when during the life of an individual particular aspects of mechanical performance should be measured; not only can the size, shape and material properties of an individual change during ontogeny, but so can its habitat, activities and ecological role. Such ecological information is also necessary to determine whether the aspects of mechanical performance being studied are biologically important, i.e. whether they affect the survivorship or fitness of the organisms. My point in raising these examples is to illustrate how ecological studies can enhance or change our understanding of biomechanical function.
Visual simulations, artificial animals and virtual ecosystems
Authors: Hokkanen J. E. I. 
Published: April 2021

ABSTRACT
This review is about a field that does not traditionally belong to biological sciences. A branch of computer animation has its mission to create active self-powered objects living artificial lives in the theoretical biology zone. Selected work, of particular interest to biologists, is presented here. These works include animated simulations of legged locomotion, flexible-bodied animals swimming and crawling, artificial fish in virtual ecosystems, automated learning of swimming and the evolution of virtual creatures with respect to morphology, locomotion and behaviour. The corresponding animations are available for downloading via the Internet. I hope that watching these intriguing pieces of visual simulation will stimulate digitally oriented biologists to seize the interactive methods made possible by ever-increasing computing power.
In vivo sequential changes in chloride cell morphology in the yolk-sac membrane of mozambique tilapia (Oreochromis mossambicus) embryos and larvae during seawater adaptation
Authors: Hiroi Junya , Kaneko Toyoji , Tanaka Masaru 
Published: April 2021

ABSTRACT
Changes in chloride cell morphology were examined in the yolk-sac membrane of Mozambique tilapia (Oreochromis mossambicus) embryos and larvae transferred from fresh water to sea water. By labelling chloride cells with DASPEI, a fluorescent probe specific for mitochondria, we observed in vivo sequential changes in individual chloride cells by confocal laser scanning microscopy. In embryos transferred from fresh water to sea water 3 days after fertilization, 75 % of chloride cells survived for 96 h, and cells showed a remarkable increase in size. In contrast, the cell size did not change in embryos and larvae kept in fresh water. The same rate of chloride cell turnover was observed in both fresh water and sea water. Using differential interference contrast (DIC) optics and whole-mount immunocytochemistry with anti-Na+/K+-ATPase, we classified chloride cells into three developmental stages: a single chloride cell without an apical pit, a single chloride cell with an apical pit, and a multicellular complex of chloride and accessory cells with an apical pit. DIC and immunofluorescence microscopy revealed that single chloride cells enlarged and were frequently indented by newly differentiated accessory cells to form multicellular complexes during seawater adaptation. These results indicate that freshwater-type single chloride cells are transformed into seawater-type multicellular complexes during seawater adaptation, suggesting plasticity in the ion-transporting functions of chloride cells in the yolk-sac membrane of tilapia embryos and larvae.