bluuebunny/crossref_metadata_2025 huggingface dataset:
Embryonic and Larval Respiration In the Arboreal foam Nests of the African Frog Chiromantis Xerampelina
Authors: Seymour Roger S. , Loveridge John P.
Published: April 2021

In Zimbabwe, female Chiromantis xerampelina construct spherical foam nests that are suspended above temporary water. The nests average 624 ml in volume and contain 854 eggs. The 1.7 mm ova have exceptionally thin jelly capsules and are dispersed in the foamy core of the nest, which is surrounded by a layer of eggless foam. At 25°C, each embryo requires 3.5 days to reach hatching at developmental stage 22, during which it consumes 30 μl of oxygen. After hatching, each larva remains in the nest for 2 more days and consumes a further 123 μl of oxygen. The fresh foam contains 77% air, which is sufficient to supply all of the oxygen requirements of the embryos until well after they hatch. Therefore, the size of the egg mass is not limited by oxygen availability as it is in many other anurans. Oxygen also diffuses into the nest from the atmosphere, but the rate is severely restricted by the wet foam, despite the presence of bubbles. Drying of the outer layer of foam greatly increases its oxygen conductance, but the larvae remain in the inner core of wet foam, where they compete for oxygen at the periphery. With further drying of the nest, the wet foam diminishes in volume and concentrates the larvae at a time when their oxygen demands are approaching the maximum. Oxygen pressures within the wet foam drop below 10 kPa and oxygen uptake by the larvae becomes progressively limited, possibly stimulating their emergence from the nest. The delay between hatching and escape from the nest permits the larvae to grow and mature to a stage at which all of the clutch can emerge simultaneously.
Odor Plumes and How Blue Crabs Use Them in Finding Prey
Authors: Weissburg Marc J. , Zimmer-Faust Richard K.
Published: April 2021

Orientation of animals using chemical cues often takes place in flows, where the stimulus properties of odorants are affected by the characteristics of fluid motion. Kinematic analysis of movement patterns by animals responding to odor plumes has been used to provide insight into the behavioral and physiological aspects of olfactory-mediated orientation, particularly in terrestrial insects. We have used this approach in analyzing predatory searching by blue crabs in response to plumes of attractant metabolites released from the siphons of live clams in controlled hydrodynamic environments. Crabs proceed directly upstream towards clams in smooth-turbulent flows and show high locomotory velocities and few periods of motionlessness. Crabs assume more indirect trajectories and display slower locomotion and more stopping in rough-turbulent flows. This degradation of foraging performance is most pronounced as flow shifts from a smooth-to a rough-turbulent regime, where the change in hydraulic properties is associated with contraction of the viscous sublayer region of the boundary layer. Because flow in this region is quasi-laminar, the viscous sublayer may be a particularly effective vehicle for chemical stimulus transmission, such that orientation is severely compromised when it is reduced or removed. Our results also suggest that rheotactic and chemical information are both necessary for successful orientation. Perception of chemical cues acts to bias locomotion upcurrent, and feedback from odorant stimulus distributions appears directly to regulate subsequent stopping and turning en route to prey. Although the mechanisms of orientation to odorant plumes displayed by insects and blue crabs are largely similar, blue crabs appear to rely more heavily on spatial and/or temporal aspects of chemical stimulus distributions than has been suggested for insect systems.
Quantitative Flow Analysis Around Aquatic Animals Using Laser Sheet Particle Image Velocimetry
Authors: Stamhuis Eize J. , Videler John J.
Published: April 2021

Two alternative particle image velocimetry (PIV) methods have been developed, applying laser light sheet illumination of particle-seeded flows around marine organisms. Successive video images, recorded perpendicular to a light sheet parallel to the main stream, were digitized and processed to map the flow velocity in two-dimensional planes. In particle tracking velocimetry (PTV), displacements of single particles in two subsequent images were determined semi-automatically, resulting in flow diagrams consisting of non-uniformly distributed velocity vectors. Application of grid-cell averaging resulted in flow field diagrams with uniform vector distribution. In sub-image correlation PIV (SCPIV), repetitive convolution filtering of small sub-areas of two subsequent images resulted in automatic determination of cross-correlation peaks, yielding flow field diagrams with regularly spaced velocity vectors. In both PTV and SCPIV, missing values, caused by incomplete particle displacement information in some areas of the images or due to rejection of some erroneous vectors by the vector validation procedure, were interpolated using a two-dimensional spline interpolation technique.

The resultant vector flow fields were used to study the spatial distribution of velocity, spatial acceleration, vorticity, strain and shear. These flow fields could also be used to test for flow in the third dimension by studying the divergence, and to detect the presence and location of vortices. The results offer detailed quantitative descriptions of the flow morphology and can be used to assess dissipated energy. The versatile character of the technique makes it applicable to a wide range of fluid mechanical subjects within biological research. So far it has been successfully applied to map the flow around swimming copepods, fish larvae and juvenile fish and the ventilation current of a tube-living shrimp.
Effects of Hypoxia on Rainbow Trout (Oncorhynchus Mykiss): Intraerythrocytic Phosphates
Authors: Val Adalberto L. , Lessard Joanne , Randall David J.
Published: April 2021

Intraerythrocytic levels of guanosine and adenosine phosphates were estimated in normoxic and hypoxic rainbow trout after intra-arterial injection with either saline or carbonic anhydrase. A significant reduction of the total pool of adenosine and guanosine was observed in hypoxic animals. Similarly, a decrease in both ATP and GTP levels occurred in hypoxic animals injected either with saline or with carbonic anhydrase. Interestingly, there was a highly significant relationship between ATP and GTP levels, indicating that they are under similar control. In addition, a significant positive relationship between nucleoside triphosphate (NTP) and Mg2+ levels was observed. It is possible that the availability of ATP and GTP to hemoglobin (Hb) may be proportionally smaller than their intraerythrocytic absolute levels. No clear relationship between intraerythrocytic NTP levels and plasma carbonic anhydrase infusion was observed, despite the significant effect of carbonic anhydrase on acid–base balance. There was a significant relationship between red blood cell pH and [NTP]:[Hb] in fish exposed to hypoxia for 48 h. No such relationship existed during the first 6 h of hypoxic exposure. Possible mechanisms accounting for the reduction in NTP levels during the initial phases of hypoxia are discussed.
Postnatal Development of Synchronous Stepping in the Gerbil (Gerbillus Dasyurus)
Authors: Blumberg-Feldman Hagit , Eilam David
Published: April 2021

During the first two postnatal weeks, Wagner’s gerbil (Gerbillus dasyurus) pups employed stepping sequences considered to be more basic than in the later stages of development and displayed alternate stepping of the legs in each girdle. In the third postnatal week, the adult mode of locomotion, the bound, became prominent and synchronous stepping dominated locomotion, gradually replacing alternate stepping. Motor performance of the gerbil pups corroborates previous studies in following a developmental motor gestalt termed ‘warm-up’, which involves an ordered incorporation of movements along three distinct spatial dimensions. In the present results, the validity of warm-up has been extended to a quantitative perspective: the order in which movement types reached their peak performance was identical to the order of their emergence in ontogeny. Transient modes of locomotion were also employed by gerbil pups during postnatal development, in accordance with changes in body morphology, indicating that there exists a causal link between body design and specific modes of locomotion.
Feeding Kinematics of Phyllomedusine Tree Frogs
Authors: Gray Lucie A. , Nishikawa Kiisa C.
Published: April 2021

Previous studies have demonstrated that the phyllomedusine hylids possess highly protrusible tongues, a derived characteristic within the family Hylidae. In the present study, the kinematics of the feeding behavior of a phyllomedusine species, Pachymedusa dacnicolor, was analyzed using high-speed video (180 frames s-1). Its behavior was compared with that of Hyla cinerea, a species with a weakly protrusible tongue. P. dacnicolor exhibits a faster rate of tongue protraction, a longer gape cycle and more variable feeding kinematics than H. cinerea. In addition, the tongue is used in a unique ‘fly-swatter’ fashion, to pin the prey to the substratum as the frog completes the lunge. The rapid tongue protraction, extended gape cycle and fly-swatter action may have evolved in response to a diet of large, rapidly moving insects. In addition, several duration variables of the feeding cycle were greater for misses than for captures and drops, which suggests that sensory feedback rather than biomechanics controls gape cycle duration.
The Mechanical Properties of fast and Slow Skeletal Muscles of the Mouse in Relation to their Locomotory Function
Authors: James Rob S. , Altringham John D. , Goldspink David F.
Published: April 2021

The mechanical properties of soleus and extensor digitorum longus (EDL) muscles from the mouse were studied using the work loop technique. Under optimum conditions, the EDL produced a maximum mean power output of 107 W kg-1 at a cycle frequency of 10 Hz. In comparison, the maximum mean power output of the soleus was 34 W kg-1 at 5 Hz cycle frequency. Video analysis of mice determined the stride frequency range to be from 2.87 Hz at a walk to 8.23 Hz at a flat-out gallop, with the trot-to-gallop transition occurring at 5.89 Hz. In vivo EDL electromyogram (EMG) activity is recorded primarily during shortening and the muscle operates in a power-generating mode. The soleus is close to isometric when EMG activity is recorded, but mechanical activity persists into the shortening phase. Both muscles are likely to operate over cycle frequency ranges just below, or at, those yielding maximal power. Soleus and EDL produced maximal power output in vitro when operating at mean sarcomere lengths of 2.58 μm and 2.71 μm respectively. These lengths are slightly above the plateau of the length–force curve predicted for rat leg muscle (2.3–2.5 μm). The sarcomere length ranges used in vivo by the soleus and EDL were determined, by fixing muscles in the extreme active positions predicted from video and cine analysis, to be 2.28–2.57 μm and 2.49–2.88 μm respectively. These ranges are both close to those shown to yield maximum power output in vitro and to the plateau of the sarcomere length–force curve.
Motor Innervation of the Oviducts and Central Generation of the Oviductal Contractions in two Orthopteran Species (Calliptamus SP. and Decticus Albifrons)
Authors: Kalogianni E. , Theophilidis G.
Published: April 2021

The oviducts of the female Decticus albifrons (Orthoptera: Tettigonidae) are innervated by six bilaterally paired neurones, while those of the female Calliptamus sp. (Orthoptera: Catantopidae) are innervated by three bilaterally paired neurones, located in the seventh abdominal ganglion. Using intracellular recording and staining, five of the six oviductal neurones of D. albifrons and the three oviductal neurones of Calliptamus sp. were physiologically and morphologically identified. All three oviductal neurones of Calliptamus sp. have a motor function. In D. albifrons, however, there is evidence for motor function in only three of the five identified oviductal neurones that appear to participate in the generation of the oviductal contractions. The remaining two identified neurones of D. albifrons have a branching pattern similar to that of motor neurones, but their physiological characteristics, large overshooting soma action potentials (30–40 mV) with a long afterhyperpolarising phase, are similar to those of the oviductal unpaired median neurones, which are known to modulate the oviductal contractions. The oviductal muscle exhibits two different modes of contractions: (a) fast and slow myogenic contractions, the fast contractions being produced by spontaneous potentials (30–40 mV) generated by some oviductal muscle fibres; and (b) neurogenic contractions caused by the rhythmic spiking of the oviductal motor neurones. This motor pattern is produced by the oviductal central pattern generator, a neural network residing in the last two abdominal ganglia (seventh and terminal abdominal ganglia) of the species examined here. When isolated both anteriorly and posteriorly, the seventh abdominal ganglion generates rhythmic oviductal contractions of lower frequency and amplitude than those recorded when the connectives between the genital ganglia are intact. The oviductal pattern generator is activated through release from descending inhibition, which originates, in Calliptamus sp., from the compound metathoracic ganglion (fused metathoracic and first three abdominal neuromeres) and in, D. albifrons, from the first free abdominal ganglion (fused second and third abdominal neuromeres).
Effect of Beat Frequency on the Velocity of Microtubule Sliding in Reactivated Sea Urchin Sperm Flagella Under Imposed Head Vibration
Authors: Shingyoji Chikako , Yoshimura Kenjiro , Eshel Dan , Takahashi Keiichi , Gibbons Ian R.
Published: April 2021

The heads of demembranated spermatozoa of the sea urchin Tripneustes gratilla, reactivated at different concentrations of ATP, were held by suction in the tip of a micropipette and vibrated laterally with respect to the head axis. This imposed vibration resulted in a stable rhythmic beating of the reactivated flagella that was synchronized to the frequency of the micropipette. The reactivated flagella, which in the absence of imposed vibration had an average beat frequency of 39 Hz at 2 mmol l−1 ATP, showed stable beating synchronized to the pipette vibration over a range of 20–70 Hz. Vibration frequencies above 70 Hz caused irregular, asymmetrical beating, while those below 20 Hz induced instability of the beat plane. At ATP concentrations of 10–100 µmol l−1, the range of vibration frequency capable of maintaining stable beating was diminished; an increase in ATP concentration above 2 mmol l−1 had no effect on the range of stable beating. In flagella reactivated at ATP concentrations above 100 µmol l−1, the apparent time-averaged sliding velocity of axonemal microtubules decreased when the imposed frequency was below the undriven flagellar beat frequency, but at higher imposed frequencies it remained constant, with the higher frequency being accompanied by a decrease in bend angle. This maximal sliding velocity at 2 mmol l−1 ATP was close to the sliding velocity in the distal region of live spermatozoa, possibly indicating that it represents an inherent limit in the velocity of active sliding. The results are consistent with the view that the sliding velocity of axonemal microtubules does not depend solely upon the local concentration of ATP, but is also dependent upon the oscillatory mechanism associated with initiation of new flagellar bends.
Heart Mitochondrial Properties and Aerobic Capacity are Similarly Related in a Mammal and a Reptile
Authors: Conley Kevin E. , Christian Keith A. , Hoppeler Hans , Weibel Ewald R.
Published: April 2021

The heart mitochondrial properties and the aerobic capacity of the rat (Sprague-Dawley breed) and the Cuban iguana (Cyclura nubila) were used to evaluate the relationship between the oxidative capacity of the heart and the maximum oxygen delivery rate. Both species are active at body temperatures of 37–39 °C, have similar heart mitochondrial volumes [Vmt; 0.43±0.02 ml (S.E.M.) in the rat and 0.48±0.02 ml in the iguana] and differ less than twofold in (29.2±1.6 and 16.9±0.6 ml min−1, respectively). We found that Vmt was closely correlated with in the rat (r2=0.77, P<0.005) and the iguana (r2=0.82; P<0.001). Furthermore, the inner mitochondrial membrane (cristae) area (Sim) per unit did not differ between the rat and the iguana (0.60±0.02 and 0.71±0.02 m2 min ml−1 O2, respectively). This correspondence of indicates that the rat and the iguana have the same cardiac oxidative capacity at the maximum oxygen delivery rate. These results suggest that, despite the differences between the cardiovascular systems of these species, the cardiac cost of delivering oxygen at the aerobic capacity is similar in this mammal and this reptile.
A V-ATPase DRIVES ACTIVE, ELECTROGENIC AND Na+-INDEPENDENT Cl−ABSORPTION ACROSS THE GILLS OF ERIOCHEIR SINENSIS
Authors: Onken Horst , Putzenlechner Max
Published: April 2021

Using biochemical and electrophysiological techniques, we have examined the proposal that an H+-ATPase is involved in Cl- uptake across the gills of the Chinese crab Eriocheir sinensis. Bafilomycin A1 (1 µ,mol l-1), a specific inhibitor of V-ATPases, was used to investigate the importance of this H+-translocating enzyme in Cl- transport across the gill. In homogenates of ion-transporting posterior gills, we found the activity of a bafilomycin-sensitive V-ATPase to be markedly higher than in the anterior gills, which are not involved in ion transport. A similar distribution was found for the Na+/K+-and the mitochondrial F1Fo-ATPase. After differential and density centrifugation, the specific activity of the V-ATPase was enriched by a factor of 5. Neither Na+/K+-and F1Fo-ATPase activities nor acid phosphatase activity copurified with the bafilomycin-sensitive ATPase activity, indicating that at least the major portion of V-ATPase activity is not of basolateral, mitochondrial or lysosomal origin. In fluorescence studies, using Acridine Orange or Oxonol V as dyes, membrane vesicles displayed ATP-dependent proton transport and membrane potential generation, which were markedly reduced in the presence of bafilomycin. In addition to these biochemical studies, we mounted split lamellae of posterior gills in an Ussing-type chamber and measured the negative short-circuit current (Isc), which was shown to reflect active, electrogenic, Na+-independent and ouabain-insensitive Cl- absorption. After the addition of 1 µ,mol l-1 bafilomycin to the external bath, this Isc was reduced to about 50–60 % of its original value. Concomitantly, the conductance of the preparation decreased by about 13 %. From these results, we conclude that an apical V-ATPase drives electrogenic Cl- uptake across the posterior gills of the Chinese crab.
Evidence for the Hormonal Function of a Crf-Related Diuretic Peptide (Locusta-Dp) in Locusta Migratoria
Authors: Patel Manju , Hayes Timothy K. , Coast Geoffrey M.
Published: April 2021

Locusta-DP is a corticotropin-releasing factor (CRF)-related diuretic peptide isolated from the migratory locust Locusta migratoria. At nanomolar concentrations, synthetic Locusta-DP stimulated fluid secretion and cyclic AMP production by Malpighian tubules isolated in vitro and increased the rate of amaranth clearance in starved locusts to levels comparable with those observed during post-feeding diuresis. The peptide also caused a marked (approximately 10 %), but short-lived, reduction in the haemolymph volume of starved locusts.

A polyclonal antiserum raised against Locusta-DP(29-46) was shown to block peptidergic signal transfer in vitro and in vivo. Pre-treatment of Locusta-DP (5 nmol l-1) with antiserum diluted 1:100 resulted in a rapid reduction in the free peptide concentration to less than 1 nmol l-1, the threshold for a measurable effect on cyclic AMP production by isolated tubules. In intact insects, passive immunization with Locusta-DP antiserum blocked increases in the rate of amaranth clearance in response to exogenous diuretic peptide or in response to feeding. The latter was due specifically to the binding of Locusta-DP, because when the relevant antibodies were preadsorbed with Locusta-DP(29-46), the antiserum had no effect on amaranth clearance by recently fed insects. This provides unequivocal evidence of a hormonal function for Locusta-DP in the control of primary urine production.
Are Muscle Fibers Within Fish Myotomes Activated Synchronously? Patterns of Recruitment Within Deep Myomeric Musculature During Swimming in Largemouth Bass
Authors: Jayne Bruce C. , Lauder George V.
Published: April 2021

The myomeric axial musculature of fish has a complex three-dimensional morphology, yet within-myomere motor patterns have not been examined to determine whether all portions of each myomere are activated synchronously during locomotion. To gain insight into recruitment patterns in the deep myomeric musculature of fish, we implanted a series of fine-wire electrodes arranged in a vertical row of six electrodes and a longitudinal row of three electrodes on both the left and right sides of each of five largemouth bass (Micropterus salmoides). After recording electromyograms (EMGs) during the burst-and-glide swimming of each fish, post-mortem dissections and X-rays determined the location of electrodes with respect to (1) the longitudinal position (by counting the underlying vertebrae), (2) the position of the myomere containing the electrode, and (3) the portion within each myomere containing an electrode. Because of the convoluted overlapping shape of the myomeres, electrodes within the vertical row of sites could be located in any one of six different myomeres. Thus, we compared muscle activity for locations with a constant longitudinal position and differing myomeric position (vertical row) and among sites with both variable longitudinal and myomeric positions. We detected significant heterogeneity in EMG onset times for sites within the vertical row of electrodes; however, the durations of the EMGs from different sites were similar. EMG onset times at more posterior longitudinal positions preceded those of more anterior longitudinal positions when electrodes of the latter site were within a more posterior myomere. Thus, the timing of EMGs was consistent with the posterior propagation of muscle activity via the sequential activation of myomeres rather than the simultaneous activation of all contractile tissue within the longitudinal span of a single vertebra. In addition, extreme epaxial and hypaxial portions of myomeres showed distinct activity patterns which did not necessarily correlate with activity in the central myomeric fibers nearer the horizontal septum.
Nitric Oxide Synthesis in Locust Olfactory Interneurones
Authors: Elphick Maurice R. , Rayne Richard C. , Riveros-Moreno Valentina , Moncada Salvador , O’Shea Michael
Published: April 2021

The brain of the locust Schistocerca gregaria contains a nitric oxide synthase (NOS) that has similar properties to mammalian neuronal NOS. It catalyses the production of equimolar quantities of nitric oxide (NO) and citrulline from L-arginine in a Ca2+/calmodulin-and NADPH-dependent manner and is inhibited by the Nw-nitro and Nw-monomethyl analogues of L-arginine. In Western blots, an antiserum to the 160 kDa rat cerebellar NOS subunit recognises a locust brain protein with a molecular mass of approximately 135 kDa. NOS is located in several parts of the locust brain, including the mushroom bodies, but it is particularly abundant in the olfactory processing centres, the antennal lobes. Here it is present in two groups of local interneurones (a pair and a cluster of about 50) that project into the neuropile of the antennal lobes. The processes of these neurones terminate in numerous glomerulus-like structures where the synapses between primary olfactory receptor neurones and central interneurones are formed. NOS-containing local interneurones have also been identified in the mammalian olfactory bulb, suggesting that NO performs analogous functions in locust and mammalian olfactory systems. As yet, nothing is known about the role of NO in olfaction, but it seems likely that it is involved in the processing of chemosensory input to the brain. The locust antennal lobe may be an ideal ‘simple’ system in which this aspect of NO function can be examined.
Fatigue Rupture of Wallaby Tail Tendons
Authors: Wang Xiao Tong , Ker Robert F. , Alexander R. Mcneill
Published: April 2021

Wallaby tail tendons fail after repeated application of stresses much lower than would be needed to break them in a single pull. We show that this is a fatigue phenomenon, distinct from the creep rupture that occurs after prolonged application of a constant stress. The two phenomena are distinguished by experiments in which tensile stress is cycled at different frequencies, ranging from 1 to 50 Hz.
Hindleg Muscle Energy and Substrate Balances In Cold-Exposed Rats
Authors: Adán C. , Ardévol A. , Remesar X. , Alemany M. , Fernández-López J. A.
Published: April 2021

Rats chronically cannulated in the carotid artery and the muscular branch of the femoral vein were subjected to a cold (4 °C) environment for up to 2 h. The changes in blood flow (measured with 46Sc microspheres) and arterio-venous differences in the concentrations of glucose, lactate, triacylglycerols and amino acids allowed the estimation of substrate (and energy) balances across the hindleg. Mean glucose uptake was 0.28 μmol min-1, mean lactate release was 0.33 μmol min-1 and the free fatty acid basal release of 0.31 μmol min-1 was practically zero upon exposure to the cold; the initial uptake of triacylglycerols gave place to a massive release following exposure. The measurement of and pH also allowed the estimation of oxygen, CO2 and bicarbonate balances and respiratory quotient changes across the hindleg. The contribution of amino acids to the energy balance of the hindleg was assumed to be low.

These data were used to determine the sources of energy used to maintain muscle shivering with time. Three distinct phases were observed in hindleg substrate utilization. (1) The onset of shivering, with the use of glucose/glycogen and an increase in lactate efflux. Lipid oxidation was practically zero (respiratory quotient near 1), but the uptake of triacylglycerols from the blood remained unchanged. (2) A substrate-energy shift, with drastically decreased use of glucose/glycogen, and of lactate efflux; utilization of triacylglycerol as practically the sole source of energy (respiratory quotient approximately 0.7); decreasing uptake of triacylglycerol and increased tissue lipid mobilization. (3) The onset of a new heat-homeostasis setting for prolonged cold-exposure, with maintenance of muscle energy and heat production based on triacylglycerol utilization and efflux from the hindleg (muscle plus skin and subcutaneous adipose masses) contributing energy to help sustain heat production by the core organs and surrounding brown adipose tissue.
Adipokinetic Hormone Stimulates Neurones in the Insect Central Nervous System
Authors: Milde Jürgen J. , Ziegler Rolf , Wallstein Markus
Published: April 2021

A simple preparation designed to screen and compare the central action of putative neuroactive agents in the moth Manduca sexta is described. This approach combines microinjections into the central nervous system with myograms recorded from a pair of spontaneously active mesothoracic muscles. Pressure injection of either octopamine or Manduca adipokinetic hormone (M-AKH) into the mesothoracic neuropile increases the monitored motor activity. Under the conditions used, the excitatory effects of M-AKH exceed those of the potent neuromodulator octopamine. This suggests that M-AKH plays a role in the central nervous system in addition to its known metabolic functions and supports recent evidence that neuropeptides in insects can be multifunctional.
Adaptive Changes in Locust Kicking and Jumping Behaviour During Development
Authors: Norman Alex P.
Published: April 2021

The hind, or metathoracic, leg of a locust is specialised, enabling it to store energy that is used to extend the tibia rapidly during kicking and jumping; behaviours which share a common motor pattern. This study describes developmental changes in kicking and jumping behaviour and relates these changes to the development of the exoskeleton and jumping performance. In mature adults and intermoult larvae, the exoskeleton is strong and kicks can readily be elicited. Before and after the adult moult, when the exoskeleton is weak, kicks can be elicited less frequently, thus avoiding skeletal damage. At these times, animals do not generate the adult motor pattern for kicking, so that extension of the tibia is powered by direct muscle contraction, rather than through the release of stored energy. The muscles of all newly moulted animals are capable of generating sufficient force to damage the leg, but 14 days later the muscles can rarely generate sufficient force to damage the leg.

To mimic the forces generated during the preparation for a kick, when the flexor and extensor tibiae muscles co-contract, the extensor muscle was stimulated electrically at a range of frequencies and the nature and occurrence of the resulting mechanical damage to components of the skeleton were assessed over a 14 day period following the adult moult. In newly moulted animals, the proximal femur partially collapses and thus protects the leg from damage before the muscles generate sufficient force to damage chronically other components of the leg. This partial collapse of the femur is reversible when the extensor muscle is activated at low frequency, but high frequencies cause permanent damage. The muscles of all animals 1 day after the moult are also capable of generating sufficient force to damage the leg, but the proximal tibia breaks most commonly in the region where the extensor muscle apodeme attaches. 5 days after the moult, the muscles in only 50 % of animals can damage the leg and most commonly the extensor muscle apodeme breaks. In mature animals, the only structure that fails is the extensor muscle apodeme, which fractures close to its point of attachment to the tibia. Damaging a metathoracic leg can significantly decrease the ability of a locust to jump and to compete for mates. Changes in the likelihood of damage to a metathoracic leg occur at predictable stages of development. Locust behaviour is modified during development, avoiding such damage.
Physiological Properties of Wind-Sensitive and Tactile Trichoid Sensilla on the Ovipositor and Their Role During Oviposition in the Locust
Authors: Kalogianni Eleni
Published: April 2021

The physiological properties of the ovipositor hair sensilla of the desert locust and their responses to wind and to direct mechanical displacement are described. The hairs on the external surfaces of the ventral and dorsal ovipositor valves respond to wind stimulation, whereas the hairs on the inner surfaces of the dorsal valves are not wind-sensitive. All ovipositor hairs, however, respond to tactile displacement. Imposed tactile stimulation reveals two physiologically distinct types of ovipositor tactile hairs: the hairs on the inner surface of the dorsal valves are high-threshold hairs (threshold angular deflection of 26–67 ° at 1 Hz) that respond phasically, whereas the hairs on the lateral and ventral areas of the ventral valves and the lateral areas of the dorsal valves are low-threshold hairs (threshold angular deflection of 6–20 ° at 1 Hz) that respond phasotonically. There is no apparent difference in the length of the two physiologically distinct types of hairs.

Both high- and low-threshold hairs are directionally sensitive, with maximal responses to proximal deflection, towards the abdomen, and are also velocity-sensitive. High-threshold hairs have velocity thresholds of 40–50 ° s-1 for some hairs and 110–140 ° s-1 for others for a deflection angle of 35 °, whereas low-threshold hairs have lower velocity thresholds of less than 5 ° s-1 for the same deflection. High-threshold hairs adapt rapidly to repetitive stimulation after as few as four cycles of stimulation at

0.5 Hz. Low-threshold hairs continue to respond after 40 cycles of stimulation at 0.5 Hz and show little adaptation to repetitive stimulation at frequencies ranging from 0.1 to 5 Hz. Low-threshold hairs respond with bursts of spikes at frequencies that reflect both the velocity and the duration of the stimulus. Furthermore, low-threshold hairs show little adaptation after 30 min of stimulation that simulates oviposition digging. It is suggested (a) that low- and high-threshold ovipositor hairs detect phasic wind and/or tactile stimuli in non-ovipositing locusts and (b) that low-threshold hairs can also signal rhythmic tactile inputs during oviposition digging.
‘Deep-Sea Spiders’ That Walk Through the Water
Authors: Marshall N. Justin , Diebel Carol
Published: April 2021

Deep-sea isopods of the family Munnopsidae exhibit four modes of swimming: forward striding, slow backward pedalling, fast backward pedalling and escape, the first two of which use asymmetric phases of leg movement. Instead of moving the left and right limbs (pereopods, P2–P7) of a segment in-phase (e.g. RP2LP2, RP3LP3, RP4LP4), as do most aquatic insects, leg movement is more like that of fast-walking insects, where closest synchrony occurs between diagonal limbs (e.g. RP2LP3, RP3LP4, RP4LP2). This is similar to the alternating tripod gait used by many animals on land to prevent them from toppling over. It therefore seems likely that this group of isopods learned to walk before they could swim.
Evidence for Protein Damage at Environmental Temperatures: Seasonal Changes in Levels of Ubiquitin Conjugates and Hsp70 in the Intertidal Mussel Mytilus Trossulus
Authors: Hofmann Gretchen E. , Somero George N.
Published: April 2021

We examined the seasonal variation in environmentally induced protein damage in natural populations of the intertidal mussel Mytilus trossulus. In order to compare the state of protein pools during seasonal variations in environmental temperature, we used solid-phase immunochemical analysis to quantify ubiquitin conjugate concentrations and relative levels of the stress protein hsp70. The two biochemical indices were selected for their cellular roles in irreversible and reversible protein denaturation, respectively. Proteins that are ubiquitinated are irreversibly damaged and are degraded by intracellular proteases; stress proteins act as molecular chaperones to re-fold thermally denatured proteins and, thus, indicate degrees of reversible protein damage. Comparisons involved mussels collected in February and August from two study sites: an intertidal site which subjected animals to a wide range of body temperatures (from approximately 10 to 35 °C in summer), and a subtidal site where animals remained submerged throughout the tidal cycle. Our results show that quantities of ubiquitin conjugates and hsp70 were greater in gill tissue from summer-collected mussels than in gills of winter-collected specimens. Ubiquitin conjugate and hsp70 levels were also greater in mussels collected from an intertidal location than in mussels from a submerged population. Our results show that the high summer temperatures normally experienced in the field are sufficient to cause increased denaturation of cellular proteins. Despite increases in the concentrations of heat shock proteins in summer-acclimatized mussels, elevated levels of irreversibly denatured, i.e. ubiquitinated, proteins were still observed, which indicates that the heat shock response may not be able to rescue all heat-damaged proteins. The energy costs associated with replacing heat-damaged proteins and with maintaining the concentrations and activities of heat shock proteins may contribute substantially to cellular energy demands. These increased energy demands may have an impact on the ecological energetic relationships of species, e.g. in the allocations of energy for growth and reproduction, and, as a consequence, may contribute to determining their distribution limits.
A Salivary Nitrophorin (Nitric-Oxide-Carrying Hemoprotein) in the Bedbug Cimex Lectularius
Authors: Valenzuela Jesus G. , Walker F. Ann , Ribeiro José M. C.
Published: April 2021

Salivary gland homogenate of the bedbug Cimex lectularius caused vasodilation of the preconstricted rabbit aortic ring in the absence of endothelium. Vasodilation was augmented in the presence of superoxide dismutase and inhibited in the presence of Methylene Blue. Utilization of the Griess reaction indicated the presence of reactive nitrogen equivalents of the order of 337±57 pg equivalent NO2- per pair of salivary glands (mean ± S.E.M.; N=3). Salivary gland homogenates have a nitrosyl-hemoprotein that releases nitric oxide in a pH-dependent manner. The fraction containing the NO-carrying hemoprotein, when separated by HPLC, caused vasodilation of the preconstricted rabbit aortic strip. Furthermore, the presence of a nitrosyl-hemoprotein in Cimex lectularius salivary gland was verified by electron paramagnetic resonance spectroscopy. It is proposed that, as in the case of Rhodnius prolixus (Triatominae), Cimex lectularius salivary glands contain a hemoprotein (nitrophorin) that carries NO from the glands to the host tissues. However, because Cimex lectularius and Rhodnius prolixus belong to different hemipteran families (Cimicidae and Reduvidae) and evolved independently to blood feeding, Cimex lectularius and Rhodnius prolixus nitrophorin may be a case of convergent evolution.
Red Muscle Motor Patterns During Steady Swimming In Largemouth Bass: Effects Of Speed And Correlations With Axial Kinematics
Authors: Jayne Bruce C. , Lauder George V.
Published: April 2021

We analyzed midline kinematics and obtained electromyograms (EMGs) from the superficial red muscle at seven longitudinal positions in four largemouth bass swimming steadily at standardized speeds of 0.7, 1.2, 1.6, 2.0 and 2.4 lengths s-1. Analysis of variance was used to test for significant variation attributable to both speed and longitudinal position. EMGs propagated posteriorly were unilateral and alternated between the left and right sides. Despite the propagation of EMGs, all the red muscle along an entire side of the fish was simultaneously active for as much as one-quarter of the locomotor cycle. When expressed as a proportion of the locomotor cycle, EMG durations at a given site did not vary significantly with speed but did vary longitudinally, ranging from values of 0.45 cycles anteriorly to 0.35 cycles posteriorly. The amplitudes of lateral displacement and bending depended on longitudinal position and also increased by a maximum of approximately 50 % with increased swimming speed, whereas for all longitudinal positions the intensity of EMGs increased approximately fourfold with increased swimming speed. Electrical activity of red muscle did not correspond simply to the time of muscle shortening. Instead, the timing of EMG onset and offset relative to both lateral bending and displacement changed significantly with both longitudinal position and increased speed, such that the phase shifts between the EMGs and kinematic values were generally greatest for posterior sites at the fastest speeds. At a single longitudinal position, the phase shift between the EMG and maximal lateral bending could change by more than one-tenth of a cycle from the slowest to the fastest swimming speed. Phase lags per body segment of EMG onset and EMG offset did not vary significantly with either swimming speed or longitudinal position. EMG offset was propagated posteriorly faster than EMG onset, and both EMG onset and EMG offset were generally propagated faster than both lateral bending and displacement. Largemouth bass have a similar number of vertebrae to carp, and these two species also have a very similar pattern of muscle activation that differs substantially from that of the trout, which has nearly twice as many vertebrae.
Ant Breathing: Testing Regulation and Mechanism Hypotheses With Hypoxia
Authors: Lighton John R. B. , Garrigan Dana
Published: April 2021

Using normoxic and hypoxic flow-through respirometry, we investigated the regulation of the closed-spiracle (C) and the nature of the fluttering-spiracle (F) phases of the discontinuous gas-exchange cycle (DGC) of the ant Camponotus vicinus. We predicted that as ambient O2 concentrations declined, DGC frequency would increase, because C phase duration would decrease (reflecting earlier hypoxic initiation of the F phase) and F phase duration would shorten (reflecting nitrogen accumulation), if convective mass inflow caused by a negative pressure gradient across the spiracles, rather than by diffusion, is the dominant F phase gas-exchange mechanism. C phase duration decreased with declining ambient O2 concentrations, as predicted. In contrast, DGC frequency decreased and F phase duration increased with decreasing ambient O2 concentrations. This was opposite to the expected trend if gas exchange in the F phase was mediated by convection, as is generally hypothesized. We therefore cannot disprove that F phase gas exchange was largely or purely diffusion-based. In addition, our data show equivalent molar rates of H2O and CO2 emission during the F phase. In contrast, during the open-spiracle phase, the duration of which was not affected by ambient O2 concentration, far more H2O than CO2 was lost. We discuss these findings and suggest that current hypotheses of F phase gas-exchange mechanisms and function in reducing respiratory water loss in adult insects may require revision.
The Role of Neurohormonal Octopamine During ‘Fight or Flight’ Behaviour in the Field Cricket Gryllus Bimaculatus
Authors: Adamo S. A. , Linn C. E. , Hoy R. R.
Published: April 2021

Octopamine has been called the ‘fight or flight’ hormone of insects. We tested this hypothesis by measuring octopamine levels in the haemolymph of field crickets after fighting, flying, courting and escape behaviours. Octopamine levels in the cricket Gryllus bimaculatus increased during aggressive (agonistic) behaviour from baseline levels of 4.5±2.1 pg μl-1 haemolymph to 24.3±15.2 pg μl-1 haemolymph, regardless of whether the cricket won or lost the encounter. Octopamine levels also increased after 5 min of flying (to 44.6±22.3 pg μl-1) and during courtship. However, crickets did not exhibit an increase in their haemolymph octopamine levels after performing an escape run. Therefore, neurohormonal octopamine shows some, but not all, of the characteristics that would be expected if it were a component of a non-specific ‘arousal’ system. Rather, octopamine may be released as a neurohormone to prepare the animal for a period of extended activity or to assist the animal in recovering from a period of increased energy demand. Antennal contact with conspecifics may provide a sensory cue that results in the release of octopamine into the haemolymph.
Effects of Bafilomycin A1 on Cytosolic pH of sheep Alveolar and Peritoneal Macrophages: Evaluation of the pH-Regulatory Role of Plasma Membrane V-ATPases
Authors: Heming Thomas A. , Traber Daniel L. , Hinder Frank , Bidani Akhil
Published: April 2021

The role of plasma membrane V-ATPase activity in the regulation of cytosolic pH (pHi) was determined for resident alveolar and peritoneal macrophages (mϕ) from sheep. Cytosolic pH was measured using 2′7′-biscarboxyethyl-5,6-carboxyfluorescein (BCECF). The baseline pHi of both cell types was sensitive to the specific V-ATPase inhibitor bafilomycin A1. Bafilomycin A1 caused a significant (approximately 0.2 pH units) and rapid (within seconds) decline in baseline pHi. Further, bafilomycin A1 slowed the initial rate of pHi recovery (dpHi/dt) from intracellular acid loads. Amiloride had no effects on baseline pHi, but reduced dpHi/dt (acid-loaded pHi nadir <6.8) by approximately 35 %. Recovery of pHi was abolished by co-treatment of mϕ with bafilomycin A1 and amiloride. These data indicate that plasma membrane V-ATPase activity is a major determinant of pHi regulation in resident alveolar and peritoneal mϕ from sheep. Sheep mϕ also appear to possess a Na+/H+ exchanger. However, Na+/H+ exchange either is inactive or can be effectively masked by V-ATPase-mediated H+ extrusion at physiological pHi values.
The Control of Ventilatory and Cardiac Responses to Changes in Ambient Oxygen Tension and Oxygen Demand in Octopus
Authors: Wells M. J. , Wells J.
Published: April 2021

Octopus vulgaris can regulate its oxygen uptake down to a of around 6.7 kPa. As the tension falls from 18.6 to 6.7 kPa (140 to 50 mmHg), PV (the pressure pulse driving the ventilatory flow, measured inside the mantle cavity) can more than double while fV (the ventilation frequency) increases by a few per cent at most. Both changes are reversed when the ambient oxygen tension is returned to normal. Cutting the visceral nerves linking the hearts and gills to the brain prevents these adaptive changes in PV and fV, as does section of the branchial nerves linking the cardiac ganglia to the gills. Responses to changes in ambient oxygen tension are very fast, beginning within two or three ventilation cycles. It is concluded that changes to PV and fV depend upon receptors in the gills and on the integrity of a nervous pathway to the brain.

Changes in oxygen tension also affect the hearts, where aortic pulse amplitude (Pa) and, to a lesser extent, heartbeat frequency (fH) fall and rise with the ambient . In this case, section of the visceral or branchial nerves has no effect. Responses are again very rapid. It is concluded that the observed fall and return to normoxic values of Pa and fH are local responses to a fall and rise in the oxygen tension of blood coming from the gills into the systemic heart.

Changes to ventilation and heartbeat can also occur in normoxic water when oxygen demand rises after feeding. These responses are not prevented by section of the visceral or branchial nerves. Possible control of ventilation and heartbeat through the neurosecretory system in the anterior vena cava is discussed.