bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Avoidance During Flight in the Locust Locusta Migratoria
Authors: Robertson R. Meldrum , Kuhnert Christopher T. , Dawson Jeff W.
Published: April 2021

In this paper, thermal avoidance in tethered flying locusts is described for the first time. Changes in body posture examined using high-speed cinematography revealed that the animals responded to a laterally positioned heat source with contralaterally directed abdomen and hindleg ruddering, behavioural patterns resembling manoeuvres observed in collision avoidance and in response to auditory signals. The analysis also showed that, during stimulation, left and right forewing depression became asymmetrical during the downstroke but remained symmetrical during the upstroke. Hindwing depression and elevation remained symmetrical during stimulus presentations. Electromyographic recordings from the left and right first basalar muscles (M97; forewing depressors) showed that contralateral depressor muscle activity was advanced by 10–12 ms relative to that on the stimulated side. There was also an increase in burst duration on the contralaterally stimulated side and an increase in wingbeat frequency of approximately 3 Hz. Ablation experiments showed that removal of the antennal flagella, which are the site of previously described thermoreceptors, did not abolish thermal avoidance manoeuvres. We conclude that thermal avoidance is triggered by an infrared sensitivity that is not mediated by the compound eyes, the ocelli or the antennal flagella.
Mapping Motor Neurone Activity to Overt Behaviour in the Leech: Internal Pressures Produced During Locomotion
Authors: Wilson R. J. A. , Skierczynski B. A. , Blackwood S. , Skalak R. , Kristan W. B.
Published: April 2021

Several behaviour patterns have been studied in the leech at both the kinematic and neuronal levels. However, very little is known about how patterns of motor neurone activity map to actual movements. Internal pressure is an essential biomechanical property in this process, being responsible for producing the rigidity and posture that allow the directed delivery of forces produced by muscle contraction. To obtain a better understanding of the biomechanical processes involved in movement of the leech, we have measured the internal pressure of the animal by placing catheters through the body wall and into the gut of intact animals showing normal patterns of behaviour.

Each type of behaviour had a characteristic pressure waveform. The elongation phase of crawling produced a rapid increase in pressure that peaked when midbody segments were maximally elongated. The pressure produced during the contraction phase of crawling depended on the type of crawl, only inchworm crawling producing a second peak. Whole-body shortening in response to a head poke also produced a pressure peak, but it had a faster rise time. Swimming produced the largest pressure, which was marked by a large sustained increase that fluctuated phasically with undulations of the body. Dual pressure recordings using two catheters demonstrated that pressure was not uniform along the length of the leech, indicating that the body cavity is functionally compartmentalised.

Injecting fluid into the gut via a recording catheter allowed us to determine the effects of increasing internal volume on pressure. In line with previous predictions made using an abstract biomechanical model of the leech hydroskeleton, we found that an increase in the volume caused a reduction in the pressure. We are in the process of constructing a more realistic biomechanical model of the leech, based on actual data reported elsewhere. The results in this paper will provide key tests for refining these models.
The Variation of Resolution and of Ommatidial Dimensions in the Compound Eyes of the Fiddler Crab Uca Lactea Annulipes (Ocypodidae, Brachyura, Decapoda)
Authors: Zeil Jochen , Al-Mutairi Maha M.
Published: April 2021

We studied variations in the optical properties of the compound eyes of Uca lactea annulipes using in vivo optical and histological techniques. The distribution of resolving power in the eyes of this fiddler crab species is typical for arthropods that inhabit flat environments: the eyes possess a panoramic equatorial acute zone for vertical resolution and a steep decrease of resolution away from the eye equator in the dorsal and ventral visual fields. The dimensions of the cellular components of the ommatidia vary accordingly: in the equatorial part of the eyes, facets are larger, and crystalline cones and rhabdoms are longer than in the dorsal and ventral parts of the eyes. Along the eye equator, horizontal resolution is low compared with vertical resolution and varies little throughout the visual field. The eyes of Uca lactea annulipes are unusual in that the gradient of vertical anatomical and optical resolution is steeper in the dorsal than in the ventral visual field. We interpret this difference as indicating that the information content of the world as seen by the crabs differs above and below the horizon line in specific and predictable ways.
Wingbeat Frequency of Birds in Steady Cruising Flight: New Data and Improved Predictions
Authors: Pennycuick C. J.
Published: April 2021

Wingbeat frequencies of 15 species of birds, observed in the field in level, cruising flight were compared with predicted frequencies, calculated according to the formula derived from an earlier sample of 32 species. All of the data were collected by the author, using the same methods throughout. The new observations were predicted well for species with low wingbeat frequencies, but were underestimated at the higher frequencies. The following revised proportionality gave the best fit of the wingbeat frequency (f) to the combined data set of 47 species: ,where m is the body mass, g is the acceleration due to gravity, b is the wingspan, S is the wing area, I is the wing moment of inertia, and ρ is the air density. As measurements of I were not available for most species, its exponent was combined with those of m and b, by assuming that I∝mb2. The following equation was fitted to the data on this basis: These formulae are dimensionally correct, according to the rules derived in the earlier paper, and the equation is also numerically correct as it stands, without requiring a multiplication factor. For allometric comparisons between geometrically similar species, where body mass and wing measurements vary together (including wing moment of inertia), the expected relationship is f∝m−1/6. If the mass alone varies, owing to feeding or consumption of fuel, while the wing measurements and other variables remain unchanged, the expected relationship is f∝m1/2. These relationships apply to any dimensionally correct formula and are not affected by adjusting the coefficients within the dimensional constraints.
An Elastic Value of Protoplasm, with Further Observations on the Viscosity of Protoplasm
Authors: Seifriz William
Published: April 2021

A technique for measuring the elastic value of living protoplasm is described. An elastic value of the cortical layer of the protoplasm of the Echinarachnius egg is given. The presence of an elastic property in protoplasm is incompatible with the emulsion hypothesis of protoplasmic structure.
The Nutrition of Mycorrhiza Plants: Calluna Vulgaris
Authors: Rayner M. C.
Published: April 2021

An account is given of the formation and Seasonal development of mycorrhiza in Ling (Calluna vulgaris). Digestion of the intracellular complex of mycelium in the mycorrhiza cells is recorded for the first time and the cytology of the process is described. Knowledge of the distribution of the endophyte in the shoot tissues has been extended, and is confirmed by experimental work on cuttings struck in sterilised sand under controlled conditions. The endophyte has been recovered and identified from the shoot. The results thus obtained are compared with those described by Christoph, whose observations are interpreted in the light of the account now given of the formation of “suppressed mycorrhiza” in roots of cuttings, and also in those of seedlings and mature plants when certain conditions exist in the rooting medium. It is pointed out that the “obligate relation” in Calluna is associated with infection and seedling development and not with mycorrhiza formation and growth. The view is expressed that plants would probably grow quite well without mycorrhiza could seedlings be raised free from infection. In nature, the formation of mycorrhiza in all roots is the rule; the activities of the endophyte and its digestion products are presumably related to the nutrition of the plant and may be correlated with its growth in particular soils. The evidence for exchange of nutritive material is stated and examined. The view has been reached that such exchange exists, with a “balance of profit” on the side of the vascular plant. In view of its application to cases for which experimental data are not available, it is suggested that the term “symbiosis” as applied to mycorrhiza plants should be used in the older sense defined by de Bary.
Dynamics of Ovarian Hypertrophy Under Experimental Conditions
Authors: Lipschütz Alexander
Published: April 2021

The number of young ova in hypertrophied or increased ovarian fragments is reduced, sometimes highly reduced. This phenomenon has been seen in five experiments on young rabbits.

It is not very likely that the diminution is an apparent one due to the increased volume of the ovarian fragment.

Ovarian hypertrophy is not due to new formation of young ova but to follicular development.

The diminution of the number of young ova is explained by the fact that in an ovarian fragment a relatively increased number of young ova are used for follicular development.

It is very probable that the increase of follicular development, as taking place in an ovarian fragment and causing hypertrophy of the latter, is due to some general factor possibly to some substance available in the body in a given amount.

The ovarian fragment which alone remains in the body, reveals a tendency to cystic degeneration ; hypertrophy is in some cases nothing else than increase in volume by formation of big follicular cysts.

In five young rabbits fifteen ovaries from animals mostly of the same litters were subcutaneously engrafted. The grafts disappeared without any exception, in any case two months after the operation. In view of the great facility with which ovarian grafts generally take in homoiotransplantation, these negative results though not proving make it probable that the taking of the ovarian graft is rendered difficult when the ovaries in situ are present and use the substances as necessary for follicular development.

In three out of six cases of rabbits containing hypertrophied ovarian fragments the uterus was normal ; the fact that the uterus was less developed in the remaining cases might be explained by the long latent period as necessary till the threshold quantity of hormones can be produced by the ovarian fragment.

I am much indebted to my former co-worker Dr Karl Wagner, now Professor of Histology at the University of Kowno, for the sections for figs. 1 to 10 and 13 to 17; to Dr H. E. V. Voss for the sections for fig. II ; and to my friend Sergej Všnjakov for the photographs.
Modern Conceptions of Blood Clotting
Authors: Pickering J. W.
Published: April 2021

Despite the large number of researches which have been made on blood coagulation, no single one of the many theories advanced satisfies the criterion of a tenable hypothesis in which all known facts should be correlated.

A better understanding of the fluidity and clotting of blood should lead to important results. On the practical side, we may hope for the elucidation of thrombosis—the formation of clots in the vessels—of the lack of coagulability in hæmophilia, of the changes in plasma during shock, and of the fatal intra-vascular clotting caused by certain snake venoms. On the theoretical side, light should be thrown on the reactions of colloids, on the mechanisms of immunity and of susceptibility, and possibly on the problems of genetics, as hæmophilia is transmitted from parent to offspring, and the existence of homologous bloods often depends on family relationship.

In this paper the current theories of blood coagulation will be reviewed briefly from the standpoint of investigations made in collaboration with my friends Drs Hewitt, de Souza, and Taylor,1-9 and evidence for a simpler view will be presented.
The Oviposition Responses of Calandra Granaria Linn
Authors: Eastham L. E. S. , McCully Sheila B.
Published: April 2021

This investigation was undertaken following the survey into the incidence of infestation of stored cereals by insects (Munro, 1940), and forms part of a comprehensive research programme initiated by that author into the problems of the biology and control of grain weevils.
On the Behaviour of Wireworms of the Genus Agriotes Esch. (Coleoptera, Elateridae)
Authors: Lees A. D.
Published: April 2021

Humidity reactions have recently been demonstrated in a number of terrestrial arthropods. In several instances–for example in Locusta migratoria (Kennedy, 1937), Culex fatigans (Thomson, 1938), Blatta orientalis (Gunn & Cosway, 1938), Tenebrio molitor (Pielou & Gunn, 1940) and in Pediculus humanus corporis (Wigglesworth, 1941)–it has been shown that such responses lead to the avoidance of moist air, a type of behaviour which is not easily associated with any specific physiological requirements. On the other hand, certain animals such as woodlice which are known to possess little capacity to resist desiccation, avoid dry, and aggregate in humid air (Gunn, 1937; Waloff, 1941); this type of behaviour is clearly of some adaptive significance.
Some Experiments on the Microscopical Demonstration of Zymohexase in Animal Tissues
Authors: Allen R. J. L. , Bourne G. H.
Published: April 2021

The presence in extracts of animal tissues and yeast of an enzyme catalysing the cleavage of hexosediphosphate (fructofuranose-1:6-diphosphate) into two molecules of triosephosphate was demonstrated by Meyerhof & Lohmann (1934a):
Experimental Production of Atrophied and Partly Deficient Limbs (Phocomelias) in the Axolotl Embryo*
Authors: Brandt Walter
Published: April 2021

The many different types and variations of deformities of limbs in animals and man are usually described and grouped from the morphological or genetical point of view. A very few biological experiments have been done for the purpose of elucidating the causes which produce special types of deformities in the embryo.
The Echolocation Calls of the Spotted Bat Euderma Maculatum are Relatively Inaudible to Moths
Authors: Fullard James H. , Dawson Jeff W.
Published: April 2021

Previous studies of the spotted bat Euderma maculatum have demonstrated that this bat emits echolocation calls that are lower in frequency, shorter in duration and fainter in intensity compared with those of most other insectivorous bats, acoustic characteristics which should render it less conspicuous to eared moths. We tested this prediction by monitoring electrophysiologically the ears of sympatric noctuoid (noctuid, arctiid and notodontid) moths in a site in western Canada. Auditory threshold curves demonstrate that most of the moths tested are less responsive to the calls of Eu. maculatum than to those of another sympatric bat, Eptesicus fuscus. Playbacks to moth ears of pre-recorded search-and approach-phase echolocation calls of Eu. maculatum and Ep. fuscus further demonstrate that the calls of Eu. maculatum are poorly detectable to moths and, in some cases, completely inaudible. We estimate that, in the wild, an average noctuoid moth would detect the calls of Eu. maculatum at distances of less than 1 m as opposed to the calls of Ep. fuscus which should be first heard at distances of 20–25 m. Although most moths are unable to adequately hear Eu. maculatum, the observation that two individuals possessed ears sensitive to this bat’s calls suggests the existence of auditory pre-adaptation to this type of echolocation.
Locomotor Design Of Dolphin Vertebral Columns: Bending Mechanics And Morphology Of Delphinus Delphis
Authors: Long John H. , Pabst D. Ann , Shepherd William R. , Mclellan William A.
Published: April 2021

The primary skeletal structure used by dolphins to generate the dorsoventral bending characteristic of cetacean swimming is the vertebral column. In the vertebral column of the saddleback dolphin Delphinus delphis, we characterize the static and dynamic mechanical properties of the intervertebral joints, describe regional variation and dorsoventral asymmetries in mechanical performance, and investigate how the mechanical properties are correlated with vertebral morphologies. Using a bending machine that applies an external load (N m) to a single intervertebral segment, we measured the resulting angular deformation (rad) of the segment in both dorsal extension and ventral flexion. Intervertebral segments from the thoracic, lumbar and caudal regions of the vertebral column were tested from five individuals. Using quasi-static bending tests, we measured the initial (low-strain) bending stiffness (N m rad−1) as a function of segment position, direction of bending (extension and flexion) and sequential cutting of intervertebral ligaments. We found that initial bending stiffness was significantly greater in the lumbar region than in adjacent thoracic and caudal regions, and all joints were stiffer in extension than in flexion. Cutting the interspinous ligaments significantly lowered the initial bending stiffness. Stiffness in extension is predicted (r2=0.554) by the length and width of the intervertebral disc and the length of the cranial vertebral body in the segment. Stiffness in flexion is predicted (r2=0.400) by the width of the nucleus pulposus, the length of the caudal vertebral body in the segment and the height of the transverse processes from the ventral surface of the vertebral body. We also performed dynamic bending tests on intervertebral segments from the lumbo-caudal joint and the joint between caudal vertebrae 7 and 8. Dynamic bending stiffness (N m rad−1) increases with increasing bending amplitude and is independent of bending frequency. Damping coefficient (kg m2 rad−2 s−1) decreases with increasing bending amplitude and frequency. Resilience (% energy return) increases from approximately 20 % at low bending amplitudes (±0.6 °) to approximately 50 % at high bending amplitudes (±2.9 °). Based on these findings, the dolphin’s vertebral column has the mechanical capacity to help control the body’s locomotor reconfigurations, to store elastic energy and to dampen oscillations.
Rates of Rewarming, Heart and Respiratory Rates and Their Significance for Oxygen Transport During Arousal From Torpor in the Smallest Mammal, the Etruscan Shrew Suncus Etruscus
Authors: Fons Roger , Sender Susanne , Peters Thomas , Jürgens Klaus D.
Published: April 2021

We investigated the process of rewarming from torpor with respect to respiratory and circulatory oxygen transport properties in the smallest mammal, the Etruscan shrew Suncus etruscus. In seven adult Etruscan shrews with a mean body mass of 2.4 g, torpor was induced by deprivation of food and a cold environment. During arousal from torpor at an ambient temperature of 22 °C, the shrews actively rewarmed from the lowest mean (±S.D.) body temperature (Tb) of 12.1±1.2 °C to 20 °C at a rate of 0.43±0.14 °C min−1, from 20 to 24 °C at a rate of 0.8 °C min−1, and from 24 to 36 °C at a rate of 1.1±0.1 °C min−1. The mean rate from 12 °C to normothermia amounted to 0.83 °C min−1, which is among the highest values recorded in mammals. During rewarming, the heart rate increased exponentially (Q10=2.2) from 100 to 800–1200 min−1, whereas the respiratory rate increased linearly from 50 to 600–800 min−1. These rates are higher than the heart and respiratory rates reported for other small mammals at the same Tb.

The fraction of brown adipose tissue (BAT) was 9.2±1.6 % of body mass, which is higher than in any other mammal. Up to a body temperature of approximately 17 °C, the heat for rewarming was mainly produced in the BAT; above this value, considerable activity of the skeletal muscles enhanced thermogenesis. Estimation of the mixed venous oxygen partial pressure showed that, at the tissue level, the rewarming process corresponds to heavy work conditions. The ventilatory system is adapted such that during rewarming, in addition to the appropriate oxygen transport capacity, there is also a capacity for hyperventilation.
Maturational Changes in Troponin T Expression, Ca2+-Sensitivity and Twitch Contraction Kinetics in Dragonfly Flight Muscle
Authors: Fitzhugh Gail H. , Marden James H.
Published: April 2021

Maximum lift production and the thermal sensitivity of lift production increase dramatically during adult maturation of Libellula pulchella dragonflies. Here, we report that the mechanistic basis for this transition appears to involve a developmental change in protein expression, which alters the Ca2+-sensitivity of muscle activation and twitch contraction kinetics. The alternatively spliced Ca2+ regulatory protein troponin T (TnT) undergoes an isoform shift during adult maturation. Skinned (demembranated) fibers of mature flight muscle are up to 13 times more sensitive to activation by Ca2+ than skinned fibers from teneral (newly emerged adult) flight muscle, and their Ca2+-sensitivity is more strongly affected by temperature. Intact muscle from mature individuals has a shorter time to peak tension and longer time to half-relaxation during twitch contractions, which is consistent with a greater Ca2+-sensitivity of mature muscle. Because it becomes activated more quickly and relaxes more slowly, mature flight muscle is able to generate, with each twitch, more force per unit area than teneral muscle; this difference in force becomes greater at high temperatures. There do not appear to be any age-related differences in actomyosin crossbridge properties, since teneral and mature flight muscles do not differ in shortening velocity, tetanic tension or instantaneous power output during isotonic contraction. Thus, variation in TnT expression appears to affect the temperature-dependent Ca2+-sensitivity of muscle activation, which in turn affects the kinetics and force production of the twitch contractions used by dragonflies during flight. This cascade of effects suggests that maturational changes in the expression of TnT isoforms may be a key determinant of overall muscle and organismal performance.
On the Mechanism of Water Vapour Sorption From Unsaturated Atmospheres by Ticks
Authors: Gaede K. , Knülle W.
Published: April 2021

The nascent salivary secretion of 41 partly dehydrated and unfed adult female Amblyomma variegatum, 5–8 months post-ecdysis, during water vapour uptake at 93.5 % relative humidity and 20 °C, had an osmolality of between 298.6 and 769.7 mosmol kg−1 (mean ± S.D. 470.3±85.8 mosmol kg−1). This range would allow water vapour uptake at relative humidities of approximately 98–99 %, but it would not suffice for lower relative humidities down to 80–85 %, the critical equilibrium humidity of A. variegatum. At this relative humidity (85 %), an osmolality of 9796 mosmol kg−1 is required for water vapour uptake. It is proposed that hydrophilic cuticle in the hypostome could play a role in water condensation and that the slightly hyperosmotic secretion of the agranular alveoli of the salivary glands might alter the water affinity at the adsorbing cuticle surface and release the adsorbed water. The water-enriched secretion would then be drawn into the mouth by the powerful suction of the pharynx. This hypothetical hydrophilic cuticle component of water vapour uptake in A. variegatum merits closer investigation. The sorption kinetics of A. variegatum support an additional ‘osmotic’ component of water vapour uptake at humidities near saturation.

A nanolitre osmometer particularly suited to sample volumes smaller than 5 nl was developed. This device does not require the transfer of fluid after collection, and its measurement range is extended beyond the 5 osmol kg−1 that can be measured using commercial apparatus.
Post-Dive Blood Lactate Concentrations in Emperor Penguins, Aptenodytes Forsteri
Authors: Ponganis P. J. , Kooyman G. L. , Starke L. N. , Kooyman C. A. , Kooyman T. G.
Published: April 2021

In order to determine an aerobic diving limit (ADL) in emperor penguins (Aptenodytes forsteri), post-dive blood lactate concentrations were measured in penguins foraging at an isolated sea ice hole. Resting lactate concentrations were 1.2–2.7 mmol l−1. Serial samples revealed that lactate level usually peaked within 5 min after dives and that 7–12 min was required for lactate concentrations to decrease from 5–8 mmol l−1 to less than 2.5 mmol l−1. Post-dive lactate level was not elevated above 3 mmol l−1 for dives shorter than 5 min. Two-phase regression analysis revealed a transition at 5.6 min in the post-dive lactate level versus diving duration relationship. All dives longer than 7 min were associated with lactate concentrations greater than 5 mmol l−1. We conclude that the ADL in emperor penguins ranges between 5 and 7 min. These are the first determinations of post-dive lactate concentrations in any free-diving bird and are currently the only physiological assessment of an ADL in an avian species.
Design Complexity and Fracture Control in the Equine Hoof Wall
Authors: Kasapi Mario A. , Gosline John M.
Published: April 2021

Morphological and mechanical studies were conducted on samples of equine hoof wall to help elucidate the relationship between form and function of this complex, hierarchically organized structure. Morphological findings indicated a dependence of tubule size, shape and helical alignment of intermediate filaments (IFs) within the lamellae on the position through the wall thickness. The plane of the intertubular IFs changed from perpendicular to the tubule axis in the inner wall to almost parallel to the tubule axis in the outer wall. Morphological data predicted the existence of three crack diversion mechanisms which might prevent cracks from reaching the sensitive, living tissues of the hoof: a mid-wall diversion mechanism of intertubular material to inhibit inward and upward crack propagation, and inner- and outer-wall diversion mechanisms that prevent inward crack propagation.

Tensile and compact tension fracture tests were conducted on samples of fully hydrated equine hoof wall. Longitudinal stiffness decreased from 0.56 to 0.30 GPa proceeding inwardly, whereas ultimate (maximum) properties were constant. Fracture toughness parameters indicated that no compromise results from the declining stiffness, with J-integral values ranging from 5.5 to 7.8 kJ m−2 through the wall thickness; however, highest toughness was found in specimens with cracks initiated tangential to the wall surface (10.7 kJ m−2). Fracture paths agreed with morphological predictions and further suggested that the wall has evolved into a structure capable of both resisting and redirecting cracks initiated in numerous orientations.
Larval Locomotion of the Lancelet Branchiostoma Floridae
Authors: Stokes M. Dale
Published: April 2021

The ontogeny of locomotion in the Florida lancelet (Branchiostoma floridae) is described for the early developmental stages through to metamorphosis. Recently hatched larvae swam at speeds up to 1 mm s−1 using their epidermal cilia; this speed decreased to approximately 0.2 mm s−1 by 60 h after fertilization. Changes in cilia-powered fluid flow could be related to changes in the distribution and density of the epidermal cilia during development. Cilia-powered hovering was the dominant behaviour until metamorphosis. The amount of energy expended by ciliating larvae ranged from 10−9 to 10−11 W depending upon the age of the larvae and the model used for estimating the power output. The majority of the energy expended was in the ciliary sublayer next to the body. The first muscular movements were seen in larvae 16 h old. These simple flexions increased in complexity during the first 72 h until a complete undulatory (approximately sinusoidal) wave was propagated down the body in the adult manner. The frequency of undulatory beating increased to approximately 10 Hz during the first 48 h, and the larval head showed a large degree of yaw. Lancelet larvae were also capable of high-speed undulations 5–10 times faster than regular swimming motions. In contrast to ciliating larvae, the energy expended during undulation was at least an order of magnitude greater (10−8 to 10−6 W) and radiated beyond the ciliary sublayer.
Direct Measurement of Flow From the Posterior Lymph Hearts of Hydrated and Dehydrated Toads (Bufo Marinus)
Authors: Jones J. M. , Gamperl A. K. , Farrell A. P. , Toews D. P.
Published: April 2021

Flow from the posterior lymph hearts of Bufo marinus was measured using Doppler flow probes. These probes were placed on the posterior vertebral vein and recorded flow as lymph was ejected from the heart. In resting, hydrated toads, mean lymph flow from one of the paired posterior lymph hearts was 25.9±4.9 ml kg−1 h−1, stroke volume was 8.9±1.4 μl kg−1 and lymph heart rate was 47.5±3.7 beats min−1. We estimate that, together, the paired posterior lymph hearts are capable of generating flows that are approximately one-sixtieth of the resting cardiac output. Mean peak systolic pressure developed by the posterior lymph hearts was 1.62±0.08 kPa. Simultaneous measurements of lymph heart pressure development and flow revealed that the outflow pore of the heart opened at a pressure of 0.71±0.04 kPa, approximately 113±5 ms into systole.

When toads were moderately disturbed, stroke volume increased by as much as fourfold with little change in lymph heart rate (<5 beats min−1). When toads were dehydrated, lymph flow decreased by 70 % at 12 h and by 80 % at 24 h. Since there was only a modest non-significant decrease in lymph heart rate (30 %), this reduction in flow was attributed to decreases in stroke volume (approximately 80 %). Lymph heart flow and stroke volume returned to control values 30 min after adding water back into the experimental chamber. Stroke volume was clearly more important in regulating lymph flow than lymph heart rate under these conditions in Bufo marinus.
The Effect of Exercise-Induced Localised Hyperthermia on Tendon Cell Survival
Authors: Birch Helen L. , Wilson Alan M. , Goodship Allen E.
Published: April 2021

Tendons that store energy during locomotion, such as the equine superficial digital flexor tendon (SDFT) and human Achilles tendon, suffer a high incidence of central core degeneration which is thought to precede tendon rupture. Although energy storage contributes to the efficiency of locomotion, tendons are not perfectly elastic and some energy is lost in the form of heat. Recent studies have shown that the central core of equine SDFT reaches temperatures as high as 45 °C during high-speed locomotion. In this study, we test the hypothesis that hyperthermia causes tendon cell death and results in tendon central core degeneration. Tendon fibroblasts cultured from the core of the equine SDFT were subjected to a temperature of 45 °C in an in vitro system for 0–180 min, and cell survival fraction was measured and compared with that for equine dermal fibroblasts and a commercial rat kidney fibroblast cell line (NRK 49F). Tendon fibroblasts were significantly more resistant to hyperthermia than NRK 49F cells after 30, 45 and 60 min of heating and significantly more resistant than dermal fibroblasts after 45 and 60 min of heating. After 10 min of heating at 45 °C, the tendon fibroblast cell survival fraction was 91±4 %, whereas heating for 10 min at 48 °C resulted in a drop in the cell survival fraction to 22±4 %. In conclusion, while temperatures experienced in the central core of the SDFT in vivo are unlikely to result in tendon cell death, repeated hyperthermic insults may compromise cell metabolism of matrix components, resulting in tendon central core degeneration.
The Flight Performance of A Damselfly Ceriagrion Melanurum Selys
Authors: Sato Machiko , Azuma Akira
Published: April 2021

The local circulation method was applied to the free forward flight of the damselfly Ceriagrion melanurum Selys. The kinematic data used in the calculations were obtained by analyzing video-taped images of damselflies in free flight in a transparent container. The inclination of the stroke plane was smaller and the flapping amplitude was larger than those of dragonflies reported in other studies on odonate flight. However, the phase shift between the fore- and hindwings agreed with none of the previously reported patterns for damselflies: the forewings lead the hindwings by approximately a quarter-period. The calculated forces were within the expected range of error. The muscle-mass-specific power was between 40 and 80W kg−1. The vorticity distribution of trailing and shed vortices in the wake was also analyzed. Strong trailing vortices were observed at the wing tips, whereas shed vortices were concentrated near the wing root as the stroke switched direction.
Comparative Study on Neural Oscillation in the Procerebrum of the Terrestrial Slugs Incilaria Bilineata and Limax Marginatus
Authors: Kawahara Shigenori , Toda Shoichi , Suzuki Yasuyoshi , Watanabe Satoshi , Kirino Yutaka
Published: April 2021

Coherent oscillatory activities in procerebral neurones have been described in Limax maximus; however, the electrical properties of the procerebrum of other terrestrial molluscs are less well understood. We have examined oscillatory activity in the procerebrum of Incilaria bilineata and Limax marginatus. The local field potential measured in the procerebrum of I. bilineata showed repetitive peaks which had the opposite polarity from those measured in L. marginatus. Optical measurement of membrane potential using a potential-sensitive dye, di-4-ANEPPS, showed that the oscillations in I. bilineata occurred mainly in the internal mass while those in L. marginatus were located in the cell mass. An analysis of the waveform revealed that the depolarizing phase of the oscillations consists of both a slow and a rapid component in both species. The rapid component was most pronounced in the internal mass of I. bilineata but was prominent in the cell mass of L. marginatus. The superior tentacle nerve, which projects to the terminal mass, also showed oscillations in synchrony with those of the procerebrum. These results suggest that oscillations in procerebral interneurones are commonly generated in a region adjacent to the terminal mass and that these oscillations may affect the membrane potential of the neurones constituting the superior tentacle nerve.
Mg2+ Transport in Plasma Membrane Vesicles of Renal Epithelium of the Mozambique Tilapia (Oreochromis Mossambicus)
Authors: Bijvelds Marcel J. C. , Kolar Zvonimir , Wendelaar Bonga Sjoerd E. , Flik Gert
Published: April 2021

To elucidate the mechanisms involved in Mg2+ transport at the apical and basolateral poles of the renal tubular epithelium, apical and basolateral plasma membrane vesicle preparations were derived from kidney tissue of freshwater- and seawater-adapted Mozambique tilapia Oreochromis mossambicus. Brush-border preparations were enriched 15.8-fold in alkaline phosphatase activity and consisted almost exclusively of right-side-out membrane vesicles. Basolateral membrane preparations were enriched 7.5-fold in Na+/K+-ATPase activity and contained resealed vesicles and leaky membrane fragments. Mg2+ association with brush-border and basolateral plasma membranes, traced using radioactive 27Mg, occurred in an osmotically active space. In all instances, Mg2+ binding to the vesicular membrane was low compared with the vesicular uptake. Mg2+ equilibration across the vesicular membrane of brush-border preparations was rapid and sensitive to the presence of extravesicular Ca2+, suggesting that the apical membrane of the renal epithelium contains a transport pathway for divalent cations. Application of various ionic gradients did not affect vesicular Mg2+ transport in apical and basolateral membrane preparations, suggesting the presence of an ion-coupled transport mechanism. ATP or ATP-γ-S did not stimulate Mg2+ fluxes, indicating that Mg2+ transport does not proceed via an ATP-driven or activated transporter. In these aspects, vesicular Mg2+ transport was similar in seawater and freshwater preparations. These results suggest that the apical membrane of renal epithelial cells lacks an active secretory Mg2+ transport mechanism. We propose that the Mg2+ conductivity of the apical membrane reflects a route for downhill Mg2+ entry and is involved in renal Mg2+ reabsorption.
Ontogeny of Central Chemoreception During Fictive Gill and Lung Ventilation in an In Vitro Brainstem Preparation of Rana Catesbeiana
Authors: Torgerson C. S. , Gdovin M. J. , Remmers J. E.
Published: April 2021

An isolated brainstem preparation of the bullfrog tadpole, Rana catesbeiana, displays coordinated rhythmic bursting activities in cranial nerves V, VII and X in vitro. In decerebrate, spontaneously breathing tadpoles, we have previously shown that these bursts correspond to fluctuations in buccal and lung pressures and to bursts of activity in the buccal levator muscle H3a. This demonstrates that the rhythmic bursting activities recorded in vitro represent fictive gill and lung ventilation. To investigate the ontogeny of central respiratory chemoreception during the transition from gill to lung ventilation, we superfused the isolated brainstems of four larval stage groups with oxygenated artificial cerebrospinal fluid at various levels of . We measured shifts in the pattern of fictive respiratory output and the response to central hypercapnic stimulation throughout development. At normal (2.3 kPa), stage 3–9 tadpoles displayed rhythmic neural bursts associated with gill ventilation, while stages 10–14 and 15–19 tadpoles produced oscillating bursting activity associated with both gill and lung respiration, and tadpoles at stages 20–25 displayed neural activity predominantly associated with lung ventilation. In stage 3–9 tadpoles, variations in of the superfusate (0.5–6.0 kPa) caused almost no change in fictive gill or lung ventilation. By contrast, stage 10–14 tadpoles showed a significant hypercapnic response (P<0.05) in the amplitude and frequency of fictive gill ventilation, which was accompanied by a significant increase (P<0.05) in the burst amplitude and respiratory output of cranial nerve X over that occurring at all other stages. The amplitude and frequency of fictive gill ventilation in stages 15–19 increased significantly (P<0.05) in response to pH reduction, but became insensitive to hypercapnia at stages 20–25. The frequency of fictive lung ventilation was unresponsive to hypercapnia in stage 10–14, increased significantly by stage 15–19 (P<0.05) and became maximal (P<0.05) in stages 20–25. Overall, we describe the ontological development of central respiratory chemoreceptors driving respiratory output in the larval amphibian, demonstrating transfer in central chemoreceptive influence from gill to lung regulation during metamorphic stages. In addition, we provide novel evidence for the stimulatory influence of central chemoreceptors on fictive gill ventilation in response to CO2.
In Situ Biomechanics of the Syrinx and Sound Generation in Pigeons
Authors: Goller Franz , Larsen Ole Næsbye
Published: April 2021

The in situ biomechanics of the vocal organ, the syrinx, was studied in anesthetized pigeons using fiberoptic instruments. The role of syringeal muscles was determined by electrical stimulation, and phonation was induced by injecting gas into the subsyringeal air sacs. This study presents the first direct observations of the biomechanical processes that occur in an intact syrinx.

Contraction of one of the syringeal muscles, the m. tracheolateralis (TL), withdraws the lateral tympaniform membranes (LTM) from the syringeal lumen, causing opening of the syringeal airways. Shortening of a second muscle, the sternotrachealis (ST), draws the syringeal cartilages closer to each other, causing the LTM to fold into the syringeal lumen. Maximal ST contraction does not lead to complete closure of the syrinx.

As air-sac pressure is increased by the injection of gas, the LTM are drawn into the syringeal lumen and balloon in a rostral direction until they touch, thus forming a fold-like valve. Air-induced phonation is always associated with vibrations of the membrane folds, suggesting that pulsatile release of air into the trachea by vibratory motion of the LTM generates sound. During air-induced phonation, strong stimulation of the TL terminates sound generation by abducting the LTM, whereas weak stimulation changes the geometry of the membrane folds, which is accompanied by changes in the acoustic structure of the sound. Stimulation of the ST has little effect on air-induced sounds.

The LTM appear to be the main sound generators, since disabling the medial tympaniform membranes (MTM) with tissue adhesive does not prevent phonation or change the frequency and amplitude structure of display coos in spontaneously vocalizing pigeons. Moreover, the activity of the syringeal muscles appears to have a mainly modulatory function, suggesting that the basic sound-generating mechanism is similar in both air-induced and natural phonation.
Mechanics of Locomotion in Lizards
Authors: Farley Claire T. , Ko T. Christine
Published: April 2021

Lizards bend their trunks laterally with each step of locomotion and, as a result, their locomotion appears to be fundamentally different from mammalian locomotion. The goal of the present study was to determine whether lizards use the same two basic gaits as other legged animals or whether they use a mechanically unique gait due to lateral trunk bending. Force platform and kinematic measurements revealed that two species of lizards, Coleonyx variegatus and Eumeces skiltonianus, used two basic gaits similar to mammalian walking and trotting gaits. In both gaits, the kinetic energy fluctuations due to lateral movements of the center of mass were less than 5 % of the total external mechanical energy fluctuations. In the walking gait, both species vaulted over their stance limbs like inverted pendulums. The fluctuations in kinetic energy and gravitational potential energy of the center of mass were approximately 180 ° out of phase. The lizards conserved as much as 51 % of the external mechanical energy required for locomotion by the inverted pendulum mechanism. Both species also used a bouncing gait, similar to mammalian trotting, in which the fluctuations in kinetic energy and gravitational potential energy of the center of mass were nearly exactly in phase. The mass-specific external mechanical work required to travel 1 m (1.5 J kg-1) was similar to that for other legged animals. Thus, in spite of marked lateral bending of the trunk, the mechanics of lizard locomotion is similar to the mechanics of locomotion in other legged animals.
Maximum Speed and Mechanical Power Output in Lizards
Authors: Farley Claire T.
Published: April 2021

The goal of the present study was to test the hypothesis that maximum running speed is limited by how much mechanical power the muscular system can produce. To test this hypothesis, two species of lizards, Coleonyx variegatus and Eumeces skiltonianus, sprinted on hills of different slopes. According to the hypothesis, maximum speed should decrease on steeper uphill slopes but mechanical power output at maximum speed should be independent of slope. For level sprinting, the external mechanical power output was determined from force platform data. For uphill sprinting, the mechanical power output was approximated as the power required to lift the center of mass vertically. When the slope increased from level to 40 ° uphill, maximum speed decreased by 28 % in C. variegatus and by 16 % in E. skiltonianus. At maximum speed on a 40 ° uphill slope in both species, the mechanical power required to lift the body vertically was approximately 3.9 times greater than the external mechanical power output at maximum speed on the level. Because total limb mass is small in both species (6–16 % of body mass) and stride frequency is similar at maximum speed on all slopes, the internal mechanical power output is likely to be small and similar in magnitude on all slopes. I conclude that the muscular system is capable of producing substantially more power during locomotion than it actually produces during level sprinting. Thus, the capacity of the muscular system to produce power does not limit maximum running speed.
Two novel tachykinin-related peptides from the nervous system of the crab Cancer borealis
Authors: Christie Andrew E. , Lundquist C. Tomas , Nässel Dick R. , Nusbaum Michael P.
Published: April 2021

Immunocytochemical and biochemical studies have indicated the presence of many neuroactive substances in the stomatogastric nervous system (STNS) of the crab Cancer borealis. In electrophysiological studies, many of these substances modulate the motor output of neural networks contained within this system. Previous work in the STNS suggested the presence of neuropeptides related to the invertebrate tachykinin-related peptide (TRP) family. Here we isolate and characterize two novel peptides from the C. borealis nervous system that show strong amino acid sequence identity to the invertebrate TRPs. The central nervous systems of 160 crabs were extracted in an acidified solvent, after which four reversed-phase HPLC column systems were used to obtain pure peptides. A cockroach hindgut muscle contraction bioassay and a radioimmunoassay (RIA) employing an antiserum to locustatachykinin I (LomTK I) were used to monitor all collected fractions. The amino acid sequences of the isolated peptides were determined by Edman degradation. Mass spectrometry and chemical synthesis confirmed the sequences to be APSGFLGMR-NH2 and SGFLGMR-NH2. APSGFLGMR-NH2 is approximately 20-fold more abundant in the crab central nervous system than is SGFLGMR-NH2. We have named these peptides Cancer borealis tachykinin-related peptide Ia and Ib (CabTRP Ia and Ib), respectively. Both peptides are myoactive in the cockroach hindgut muscle contraction bioassay, with CabTRP Ia being approximately 500 times more potent than CabTRP Ib. RIA performed on HPLC-separated C. borealis stomatogastric ganglion (STG) extract revealed that CabTRP Ia is the only detectable TRP-like moiety in this ganglion. Incubation of synthetic CabTRP Ia with the isolated STG excited the pyloric motor pattern. These effects were suppressed by the broad-spectrum tachykinin receptor antagonist Spantide I. Spantide I had no effect on the actions of the unrelated endogenous peptide proctolin in the STG. There was no consistent influence of CabTRP Ib on the pyloric rhythm. Given its amino acid sequence and minimal biological activity in the crab, CabTRP Ib may be a breakdown product of CabTRP Ia.