bluuebunny/crossref_metadata_2025 huggingface dataset:
Fast Continuous Swimming of Saithe (Pollachius Virens): a Dynamic Analysis of Bending Moments and Muscle Power
Authors: Hess F. , Videler J. J.
Published: April 2021

This paper deals with the hydrodynamics and internal dynamics of fish swimming. Our analysis starts from kinematic data obtained for fast swimming saithe, and treats the fish as a flexible elongated body. The distribution along the body of the lateral bending moment and the bending power generated inside the fish are computed as well as the power spent on the water. The computed thrust implies a drag coefficient (based on wetted surface area) of about 0·007, which is probably an over-estimate. Our major result is that the bending moment does not travel as a running wave from head to tail like the lateral body curvature does, but behaves as a standing wave. The left and right sides produce alternate contractions simultaneously over the whole body length. This finding is in agreement with myographic data from the literature.
The Kinematics of Swimming in Anuran Larvae
Authors: Wassersug Richard J. , Hoff Karin Von Seckendorf
Published: April 2021

The kinematics of swimming in tadpoles from four species of anurans (Rana catesbeiana Shaw, Rana septentrionalis Baird, Rana clamitans Latreille and Bufo americanus Holbrook) was studied using computer-assisted analysis of high speed (⩾200 frames s− 1) ciné records.

Tadpoles exhibit the same positive, linear relationship between tail beat frequency and specific swimming speed commonly reported for sub-carangiform fishes. Tadpoles show an increase in the maximum amplitude of the tail beat with increasing swimming speed up to approximately 4 lengths s− 1. Above 4 lengths s− 1, amplitude approaches an asymptote at approximately 25% of length. Tadpoles with relatively longer tails have lower specific amplitudes. Froude efficiencies for tadpoles are similar to those reported for most subcarangiform fishes. Bufo larvae tend to have higher specific maximum amplitude, higher tail beat frequencies, lower propeller efficiencies (at least at intermediate speeds) and substantially less axial musculature than do comparable-sized Rana larvae. These differences may relate to the fact that Bufo larvae are noxious to many potential predators and consequently need not rely solely on locomotion for defence. Tadpoles exhibit larger amounts of lateral movement at the snout than do most adult fishes. The point of least lateral movement during swimming in tadpoles is at the level of the semi-circular canals, as assumed in models on the evolution of the vertebrate inner ear. Passive oscillation of anaesthetized and curarized tadpoles at the base of their tail produces normal kinematics in the rest of the tail. This supports the idea that muscular activity in the posterior, tapered portion of the tadpole tail does not serve a major role in thrust production during normal, straightforward swimming at constant velocity. The angle of incidence and lateral velocity of the tail tip as it crosses the path of motion are not consistent with theoretical predictions of how thrust should be generated. The same parameters evaluated at the high point of the tail fin (approximately midtail) suggest that that portion of the tail generates thrust most effectively. Ablation of the end of the tail in passively oscillated tadpoles confirms that the terminal portion of the tadpole tail serves to reduce excessive amplitude in the more anterior portion of the tail, where most thrust is generated. The posterior portion of the tail is important in reducing turbulence around a tadpole. It may also function to produce thrust during irregular, intricate movements, such as swimming backwards. Tadpoles are comparable to subcarangiform fishes of similar size in their maximum swimming speed and mechanical efficiency, despite the fact that they have much less axial musculature and lack the elaborate skeletal elements that stiffen the fins in fishes. The simple shape of the tadpole tail appears to allow these animals efficient locomotion over short distances and high manoeuvrability, while maintaining the potential for rapid morphological change at metamorphosis.
Electroneutral Na+-2 Cl−-Leucine Cotransport by Lobster Hepatopancreatic Brush-Border Membrane Vesicles
Authors: Ahearn Gregory A. , Clay Laurel P.
Published: April 2021

Uptake of L-[3H]leucine by lobster hepatopancreatic brush-border membrane vesicles was stimulated by a transmembrane NaCl gradient (o>i), but not by identical gradients of NaSCN or other Cl− salts (e.g. K+, Li+, NH4+, Cs+ or choline), suggesting that amino acid transfer depended upon both Na+ and Cl−. In NaCl medium at acidic pH, leucine uptake was largely electroneutral and unresponsive to a transmembrane potential generated by permeable anions; however, in Na+-free medium, amino acid transport was strongly electrogenic under the same conditions. Leucine influx occurred by a combination of two carrier processes at physiologically acidic pH. One exhibited an influx Kt of 0·59 mmol 1−1, a JM of 390pmol mg protein−1 s−1 and a cotransport stoichiometry of 1 Na+ : 2 Cl+: 1 leucine. This process was most strongly cis-inhibited by the nonpolar amino acids phenylalanine, methionine and isoleucine, and most weakly inhibited by the more polar species methylaminoisobutyric acid (MeAlB), hydroxyproline, glutamate and arginine. The second leucine carrier system showed a very low binding affinity and could not be distinguished from diffusion, was Na+-and Cl−-independent, and was cis-inhibited by more polar amino acids such as lysine, hydroxyproline, MeAIB, alanine and glutamate. These results suggest that brush-border leucine transport in lobster hepatopancreas at acidic pH may occur by a combination of a modified L-system, that includes ion cosubstrates, and either by a second undefined Na+-independent process with a broad structural specificity or by multiple Na+-independent processes.
The Effects of External Salinity on the Drinking Rates of the Larvae of Herring, Plaice and Cod
Authors: Tytler P. , Blaxter J. H. S.
Published: April 2021

Drinking responses to salinity change in the larvae of herring (Clupea harengus L.), plaice (Pleuronectesplatessa L.) and cod (Gadus morhua L.) were measured from the time course of uptake of dextran labelled with tritium, following immersion in solutions of 32‰ and 16‰ sea water. The yolk sac and first feeding larval stages of all three species drink in both salinities. Furthermore, post-yolk sac stages appear to adjust their drinking rates to compensate for different salinities in a manner similar to that of the adults. Drinking rates in 32‰ sea water are approximately double those in 16‰. Mass-related drinking rates of larvae are higher than those in adults, but the differences do not match the differences in surface area to mass ratios, suggesting that larval skin is less permeable to water than is adult gill epithelium. Water absorption is indicated by the evidence of concentration of dextran in the gut. The estimates of drinking rates from tritiated dextran uptake are supported by epifluorescence microscopical measurements of the uptake of fluorescein isothiocyanate dextran.
Cardiac Response to Voluntary Diving in Tufted Ducklings (Aythya Fuligula)
Authors: Keijer E. , Butler P. J. , Woakes A. J.
Published: April 2021

Heart rate was monitored in tufted ducklings during first-ever and subsequent voluntary whole-body dives. Although the cardiac response to first-ever dives varied between individuals, the average response to these dives, to the following 20 dives, and to dives of longer duration closely resembled the response seen in adult tufted ducks. These results indicate that the cardiac response to voluntary diving in the tufted duck does not result from habituation of the classical bradycardia seen during involuntary diving.
The Significance of Fur Structure for Solar Heat Gain in the Rock Squirrel,Spermophilus Variegatus
Authors: Walsberg Glenn E.
Published: April 2021

The coats of birds and mammals typically vary through their depth in structure, insulation and optical qualities. Physical models predict that such variation can substantially affect the solar heat load acquired by an animal. This study quantifies the consequences of complex coat structure for solar heat gain in the rock squirrel (Spermophilus variegatus (Erxleben, 1777)), a species normally exposed to intense solar radiation.

This species’ pelage consists of two well-defined layers: a dense inner coat of fine, dark hairs, and a sparse outer coat of coarse, light hairs. The optics, structure and thermal insulation of the inner and outer coats are quantified and used to predict rates of radiative heat gain using a physical model. The radiative heat load measured at the skin compares well with model predictions. The validated model is then used to explore the consequences for solar heat gain of varying the relative proportions of the inner and outer coat layers. Results demonstrate that the ratio of inner to outer coat depths occurring in rock squirrels is very near that theoretically predicted to minimize solar heat gain. This indicates that optimization of fur structure may represent an effective means of adjusting solar heat gain independent of coat insulation and surface coloration.
Depression of Aerobic Metabolism and Intracellular pH by Hypercapnia in Land Snails,Otala Lactea
Authors: Barnhart M. Christopher , McMahon Brian R.
Published: April 2021

The pulmonate land snail Otala lactea undergoes simultaneous hypercapnia, hypoxia, extracellular acidosis and metabolic depression during dormancy. We tested the effects of ambient hypercapnia and hypoxia on oxygen consumption and on extracellular and intracellular pH of active (i.e. non-dormant) individuals. Active snails reduced by 50% within 1h when exposed to 65 mmHg (1 mmHg = 133·3 Pa) ambient and by 63% in 98 mmHg. These levels of CO2 are within the range that occurs naturally in the lung and blood during dormancy. of hypercapnic snails remained below that of controls for the duration of exposure (up to 9 h) and returned to control levels within 1 h when CO2 was removed. Both pHe and whole-body pHi (measured using [14C]DMO) fell with increasing haemolymph by approximately 0·71og. Critical ( -limiting) ambient of active snails was 90 mmHg in the absence of CO2 and dropped to 50 mmHg when was reduced 45% by exposure to CO2. Estimated critical at the lower typical of dormancy is well below the typical lung of dormant Otala, suggesting that in the lung does not normally limit oxygen consumption during dormancy. These results support the hypothesis that hypercapnia or resulting respiratory acidosis depresses metabolic rate during dormancy, and argue against a limitation of by hypoxia.
Metabolic Costs of Growth and Maintenance in the Toad,Bufo Bufo
Authors: Jørgensen C. Barker
Published: April 2021

Metabolic costs of growth and maintenance were determined from the relationship M (metabolism) = m + nG (growth), where m is the metabolic rate at the feeding level at which growth is zero. In the past, the slope n was interpreted as indicating the metabolic costs of growth, and the costs of maintenance that arise with the increase in body mass were disregarded. These costs are included in n. In female toads, Bufo bufo, feeding at different rates, the uncorrected value of n was 0·44, when metabolism and growth were expressed as kJ kJ−1. After correction for increased metabolic maintenance expenditure with increased body mass, the value became 0·35, indicating that the physiological costs of growth were equivalent to about one-third of the body mass deposited. Metabolic costs of growth accounted for 80% of the increase in metabolism with growth, leaving 20% for costs of maintenance. At maximum growth rate the metabolic costs of growth amounted to about 60% of the total metabolism, total mass-specific metabolic rate being 2·5 times the rate at zero growth.

The physiological costs of growth in young toads were compared with the costs in teleosts. Recalculation of published data on the relationship between metabolism and growth in the African catfish Clarias lazera indicated that the metabolic costs of growth amounted to about 28% of body mass deposited. The costs represented about 80% of the increase in metabolism with growth.

The physiological costs of growth are several times higher than the net biochemical costs of synthesis of the macromolecules constituting the increase in body mass.
Early Abrupt Recovery From Ataxia During Vestibular Compensation In Goldfish
Authors: Ott Janet F. , Platt Christopher
Published: April 2021

Vestibular compensation was studied in goldfish that had had the utriculus and semicircular canal organs unilaterally removed. Characteristic postoperative behavioural deficits of postural asymmetry were quantitatively scored. Operated animals were compared with those subject to the same duration of anaesthesia and restraint during a sham operation. The period of several minutes following the operation was characterized by severe postural asymmetry and locomotor ataxia. In the operated fish, but not the sham-operated ones, the eyes rolled tonically towards the operated side without nystagmus, the body was flexed towards the operated side, and any swimming was disoriented with rolling motion towards the operated side. These deficits lasted less than 30 min after revival from the anaesthesia. All three behavioural deficits ended abruptly within 1 min of each other for individual fish, and normal, nearly upright swimming was then maintained, even in the dark. We interpret this recovery as one of the first stages in the central process of vestibular compensation. The unusually abrupt end of these deficits in adult goldfish compared with that in other vertebrates suggests a remarkable capacity for the central nervous system to adapt. The speed of recovery of three distinct motor outputs supports models of early compensation that utilize central modulation or gain control of existing pathways, rather than anatomical reorganization.
Modes of Ammonia Transport Across the Gill Epithelium of the Dogfish Pup (Squalus Acanthias)
Authors: Evans David H. , More Kane J.
Published: April 2021

The modes of ammonia transport across the gill epithelium of the dogfish pup (Squalus acanthias) were investigated using an isolated, perfused head preparation. During perfusion for 2–3 h there was no obvious oedema of gill lamellae, the head was haemodynamically responsive to near-in-vivo concentrations of adrenaline, and the transepithelial potential was +1·9mV (perfusate relative to irrigate) and was unaffected by any of the potential inhibitors used in these studies. The rate of ammonia efflux was somewhat above in vivo levels, was not due to structural leaks (which averaged less than 1%), declined by 17% during a second, 20-min efflux period, but was stable during a third efflux period. Addition of bumetanide to the perfusate inhibited ammonia efflux by 17% compared with the control, but subsequent addition of ouabain had no effect. Amiloride added to the irrigate in the presence of ouabain in the perfusate had no effect on ammonia efflux. Ammonia efflux was stimulated by specific increases in perfusate much more (1100 times) than by specific increases in perfusate NH4+ concentrations. Given a pK of ammonia of 9·75, we calculate that 6% of the total ammonia efflux is via ionic diffusion of NH4+, 77% via non-ionic diffusion of NH3, and 17% via a bumetanide-sensitive Na++NH4++2C1− cotransport system. Basolateral or apical Na+/NH4+ exchange apparently is not involved in ammonia transport across this epithelium.
Ion-Selectivity of Single Glutamate-Gated Channels in Locust Skeletal Muscle
Authors: Kits K. S. , Usherwood P. N. R.
Published: April 2021

The ion-selectivity of the extrajunctional glutamate-gated ion channel in locust extensor tibiae muscle was studied using the patch-clamp technique. The alkali metal ions Li+, Na+, K+, Rb+ and Cs+ were all highly permeant, with reversal potentials close to 0mV. Both complete and partial replacement of Na+ (180 mmol I−1 in standard saline) showed that conductance (γ) increased in the order Li+< Na+< Cs+< Rb+ (approx. 70–125 pS), γK being close to γCs. The channel was impermeable to the large organic monovalent ions tetramethyl ammonium, guanidinium and choline, and permeable to the smaller ammonium ion. Divalent cations (Ca2+ and Mg2+) did not contribute measurably to the ionic current. Indications were obtained that high concentrations of Mg2+ or Ca2+ block the channel. The results suggest that the glutamate-gated channel combines a high conductance with a restricted ion-selectivity, based on ion charge and size, the conductance being dependent on the dehydration energy of the ionic species.
Head-Bobbing During Walking, Running and Flying: Relative Motion Perception in the Pigeon
Authors: Davies Mark N. O. , Green Patrick R.
Published: April 2021

Measurements of head and body velocity were made by single-frame analysis of films showing pigeons walking, running, flying towards a perch and taking off from the ground. A rhythm of head velocity was always observed in the first three situations, but never in the last. During walking, this head-bobbing rhythm resulted in stabilization of the head relative to the surroundings for a part of each cycle. During running or flying towards a perch, this stabilization did not occur, and the head continued to move forwards throughout the cycle. The velocity of head movement at the minimum of the cycle increased smoothly with body speed in the range of body speeds from 75cms−1 upwards, with no indication of any discontinuity between running and flight. The results provide evidence that head-bobbing is not a mechanical consequence of cursorial or flight activity, and that its visual functions must include others besides stabilization of the retinal image. It is suggested that head-bobbing has the dual function of amplifying relative motion in the retinal image during the thrust phase, making the detection of food objects more likely, while allowing detection of object motion during the hold phase.
Kinematics of the Tongue-Bite Apparatus in Osteoglossomorph Fishes
Authors: Sanford Christopher P. J. , Lauder George V.
Published: April 2021

Osteoglossomorph fishes are characterized by the possession of three sets of jaws used during the capture, maceration and swallowing of prey. One of these jaw systems is a remarkable tongue-bite apparatus used during the intraoral crushing and shredding of prey. Kinematics of the tongue-bite apparatus were quantified, using 200 frames s−1 video and film records of feeding in three genera of osteoglossomorph fishes (Osteoglossum, Pantodon and Notopterus) to examine the biomechanics and function of this mechanical system. Two distinct chewing behaviors associated with the tongue-bite apparatus were identified: raking and open-mouth chewing. In all three species, raking behavior involves holding the prey firmly in the mandibular jaws while the teeth of the tongue-bite apparatus are moved into the prey. However, other aspects of raking behavior are significantly different among the species: for example, only Notopterus uses extensive posterior movement of the pectoral girdle to pull basihyal teeth through the prey. In both Osteoglossum and Pantodon there is little motion of the pectoral girdle, and neurocranial elevation plays the major mechanical role in prey reduction, but there are also kinematic differences between Osteoglossum and Pantodon during raking. The kinematics of open-mouth chewing behavior are also significantly different among the three species. Thus, osteoglossomorph fishes share a similar morphology of the tongue-bite apparatus derived from a common ancestor, but have acquired independent kinematic specializations associated with its use.
Effects of Vagal Sensory Input on the Breathing Rhythm of the Carp
Authors: De Graaf P. J. F. , Roberts B. L.
Published: April 2021

Electrical stimulation of an epibranchial vagal ganglion, which innervates the gill region, had a marked influence on the respiratory rhythm of the carp Cyprinus carpio. Vagal input could initiate ventilation in fish displaying intermittent respiration. In fish breathing steadily, vagal stimuli could reset the respiratory rhythm by modifying the existing breathing cycle. An increase of stimulus intensity evoked a cough-like movement, thus delaying the onset of following cycles. Rhythmic stimulation, at intervals not more than 10 % longer or shorter than the breathing cycle period, could entrain the respiratory rhythm in a one-to-one ratio. Larger differences between the stimulation interval and the period of the breathing cycle resulted in either a cyclic modification of the respiratory cycle period or entrainment patterns with coupling ratios of 2:1 or 2:3. Coughing decreased in frequency or even stopped during rhythmic vagal stimulation.
Camouflage by Disruptive Illumination in Leiognathids, A Family of Shallow-Water, Bioluminescent Fishes
Authors: Mcfall-Ngai Margaret , Morin James G.
Published: April 2021

Leiognathids are shallow-water, Indo-West Pacific fishes that have a circumeso-phageal, bacterial light organ. Visual observations of living fishes revealed a mottled ventral luminescence pattern, which was analyzed both behaviorally and morphologically. In behavioral experiments, these fishes responded to increases in intensity of downwelling light with increases in the intensity of ventral luminescence. However, while the absolute luminescence levels tracked the ambient light levels, they did not increase in direct proportion to those of increasing downwelling light; luminescence levels were closer to the intensity of downwelling light at low light levels.

The tissues that intervene between the internal light organ and the external environment are responsible for the observed mottled pattern of the ventral luminescence. Furthermore, these tissues, which have been incorporated into the light organ system, are involved in the control of the intensity, spectral quality and angular distribution of the fish’s luminescence. The spectral peak of the bacterial luminescence from whole fish (500 nm) was shifted about 10 nm towards the green relative to the spectral peak of cultured light organ symbionts (485–490nm). The luminescence had the greatest intensity of outward expression at an angle of 20–25° from the ventral midline and was undetectable dorsally. The ventral illumination behavior of leiognathids, with their associated morphology, is compared and contrasted with the counterillumination systems that have been described in a number of mesopelagic fishes, shrimps and squids.
White Muscle Intracellular Acid–Base and Lactate Status Following Exhaustive Exercise: A Comparison Between Freshwater- and Seawater-Adapted Rainbow Trout
Authors: Tang Yong , Boutilier Robert G.
Published: April 2021

The intracellular acid-base status of white muscle of freshwater (FW) and seawater (SW) -adapted rainbow trout was examined before and after exhaustive exercise.

Exhaustive exercise resulted in a pronounced intracellular acidosis with a greater pH drop in SW (0.82 pH units) than in FW (0.66 pH units) trout; this was accompanied by a marked rise in intracellular lactate levels, with more pronounced increases occurring in SW (54.4 mmol 1−1) than in FW (45.7 mmol 1−1) trout. Despite the more severe acidosis, recovery was faster in the SW animals, as indicated by a more rapid clearance of metabolic H+ and lactate loads.

Compartmental analysis of the distribution of metabolic H+ and lactate loads showed that the more rapid recovery of pH in SW trout could be due to (1) their greater facility for excreting H+ equivalents to the environmental water [e.g. 15.5% (SW) vs 5.0% (FW) of the initial H+ load was stored in external water at 250min post-exercise] and, to a greater extent, (2) the more rapid removal of H+, facilitated via lactate metabolism in situ (white muscle) and/or the Cori cycle (e.g. heart, liver). The slower pH recovery in FW trout may also be due in part to greater production of an ‘unmeasured acid’ [maximum approx. 8.5 mmol kg−1 fish (FW) vs approx. 6 mmol kg−1 fish (SW) at 70–130 min post-exercise] during the recovery period. Furthermore, the analysis revealed that H+-consuming metabolism is quantitatively the most important mechanism for the correction of an endogenously originating acidosis, and that extracellular pH normalization gains priority over intracellular pH regulation during recovery of acid-base status following exhaustive exercise.
The Discharge ofIn SituNematocysts of the Acontia ofAiptasia Mutabilisis A Ca2+-Induced Response
Authors: Santoro Giuseppe , Salleo Alberto
Published: April 2021

The ionic events leading to discharge of in situ nematocysts were investigated in acontia excised from Aiptasia mutabilis Gravenhorst. The effect on discharge of various ionic solutions and ion channel blockers was tested. In the absence of Ca2+ in the medium no discharge was elicited, whatever the composition of the medium. In the presence of 10 mmol l−1 Ca2+ total discharge was induced by NaSCN, Nal, choline iodide and KI, whereas KCl induced both discharge and extrusion of undischarged nematocysts. The latter effect was prevented by La3+ but not by 4-aminopyridine (4-AP) and tetraethylammonium (TEA+). Alcian Blue induced total discharge. NaCl and choline chloride were ineffective. The discharge induced by lyotropic anions depended on Ca2+ concentration and was prevented by the Ca2+ channel blockers La3+, Co2+ and Cd2+, but not by verapamil. It is proposed that the discharge of in situ nematocysts is caused by Ca2+ conductance through the cell membrane of either the nematocyte or the supporting cell. Furthermore, cyclic AMP and cyclic GMP do not seem to be involved as second messengers in the discharge process. The combined effects of the metabolic poisons dinitrophenol (DNP) and monoiodoacetic acid did not affect the discharge process.
Mechanics of A Rapid Running Insect: Two-, Four-and Six-Legged Locomotion
Authors: Full Robert J. , Tu Michael S.
Published: April 2021

To examine the effects of variation in body form on the mechanics of terrestrial locomotion, we used a miniature force platform to measure the ground reaction forces of the smallest and, relative to its mass, one of the fastest invertebrates ever studied, the American cockroach Periplaneta americana (mass=0·83g). From 0·44–1·0ms−1, P. americana used an alternating tripod stepping pattern. Fluctuations in gravitational potential energy and horizontal kinetic energy of the center of mass were nearly in phase, characteristic of a running or bouncing gait. Aerial phases were observed as vertical ground reaction force approached zero at speeds above 1ms−1. At the highest speeds (1·0–1·5ms−1 or 50 body lengths per second), P. americana switched to quadrupedal and bipedal running. Stride frequency approached the wing beat frequencies used during flight (27 Hz). High speeds were attained by increasing stride length, whereas stride frequency showed little increase with speed. The mechanical power used to accelerate the center of mass increased curvilinearly with speed. The mass-specific mechanical energy used to move the center of mass a given distance was similar to that measured for animals five orders of magnitude larger in mass, but was only one-hundredth of the metabolic cost.
Feeding, Energy Processing Rates and Egg Production in Painted Lady Butterflies
Authors: Hainsworth F. Reed , Precup Elizabeth , Hamill Tracy
Published: April 2021

Volume and energy ingestion rates, meal sizes (intakes to satiation) and meal frequencies were measured for previously unfed adult painted lady butterflies (Vanessa cardui L.) fed sucrose solutions or nectar from Lantana camera flowers in the laboratory. Volume and energy rates of crop emptying, assimilation efficiencies and mature egg production over 1 week were measured for V. cardui fed on sucrose solutions to assess mechanisms for and consequences of maximizing net meal energy. Viscosity reduced volume ingestion rates as sugar concentration increased, and 35–52.5% (w/v) sucrose produced a maximum rate of energy gain from sucrose solutions. Ingestion rates were lower from Lantana flowers. Increasing Lantana nectar concentration from 33 to 70% sucrose would produce about the same rate of energy gain for a meal. Virtually all ingested sugars were assimilated. Energy processing rates of 30 μl meals did not vary with sex, varied little with concentration and were 12–30 times the rate of energy use for maintenance. For females this may be due to the linear dependence of mature egg production on the amount of sugar ingested. Average meal timing compensated for variations in food concentration. Meals may be initiated before complete crop emptying, and this would increase the overall rates of energy processing, particularly for small meals. If Vanessa are not time-constrained while foraging, selecting concentrated nectars would decrease foraging frequency and increase the number of mature eggs produced after a meal.
Temperature Sensitivity of Graded Synaptic Transmission in the Lobster Stomatogastric Ganglion
Authors: Johnson Bruce R. , Peck Jack H. , Harris-Warrick Ronald M.
Published: April 2021

We examined the temperature sensitivity of graded chemical synaptic strength within the pyloric circuit of the spiny lobster stomatogastric ganglion. Cooling from 20.4°C to 11.3°C reduced the graded synaptic potential (GSP) amplitude at all six pyloric synapses tested. Cooling appeared to reduce the slope of the linear part of the input-output curve at three of these synapses, and did not significantly alter the threshold for transmitter release at any synapses. Pairs of neurons with a presynaptic pyloric dilator (PD) cell showed reductions in graded synaptic strength at 16.5 °C but those with presynaptic lateral pyloric (LP) or ventral dilator (VD) cells did not. A generalized decrease in input resistance is not responsible for the reduced GSP amplitude upon cooling, as determined by input resistance, action potential amplitude and electrical coupling measurements. We conclude that cooling reduces graded chemical strength by a direct synaptic action. Since the PD and VD cells use the same transmitter and act on some of the same postsynaptic cells, their differential sensitivity to cooling further suggests a presynaptic site of action. The temperature range used in our experiments encompasses the range that the animal normally encounters in nature. Thus, the relative importance of graded synaptic interactions in generating the pyloric motor rhythm may vary with transient changes in temperature.
Dopamine as A Neuroactive Substance in the Jellyfish Polyorchis Penicillatus
Authors: Chung Jun-Mo , Spencer Andrew N.
Published: April 2021

Recent studies have shown that nerve-rich tissues in the margin of Polyorchis penicillatus (Eschscholtz), one of the hydromedusae, contain dopamine. The present experiments were conducted to determine the physiological action of dopamine at the cellular level. In the current-clamp mode, dopamine, ranging from 10−8 to 10−3moll−1, applied to cultured swimming motor neurons of this jellyfish produced hyperpolarizations accompanied by a decrease of firing rate or complete inhibition of spiking produced by anodal break excitation. Dopamine in the voltage-clamp mode elicited outward currents at more positive levels than −55 mV, which is the reversal potential of the response. The results of a series of ionic experiments suggest that the inhibitory effect of dopamine is caused by an increased permeability to potassium ions.
Kinematics and Performance Capacity for the Concertina Locomotion of A Snake (Coluber Constrictor)
Authors: Jayne Bruce C. , Davis James D.
Published: April 2021

We used a motorized treadmill to determine the endurance (from 4.2 to 5.6cm s−1) and burst speed of five Coluber constrictor Linnaeus performing concertina locomotion in tunnels 3, 5 and 7cm wide. The snakes had greatest average endurance at 4.2cms−1 within the 5cm wide tunnel (80min), and the average endurance of snakes moving in the 3 cm tunnel (24 min) was significantly lower than that observed for either the 5 or 7 cm tunnel at the same speed. In contrast to endurance capacity, there was no statistically significant effect of tunnel width on burst speed, and mean values ranged from 13.5 to 16.8 cm s−1. The fastest burst speed observed was 20.8 cm s−1 in a 7 cm tunnel. Analysis of variance on kinematic variables measured from videotapes made of the endurance trials revealed highly significant effects of both speed and tunnel width on kinematics. As the tread speed increased among different endurance trials, the snakes primarily increased the frequency of movements and increased the average forward speed during the moving phase. However, the snakes did not significantly alter either the distance moved per cycle or the proportion of time spent moving in response to different tread speeds used in the endurance trials. Decreased tunnel width caused snakes (1) to move a smaller distance per cycle, (2) to use more regions of static contact with the sides of the tunnel, and (3) to orient the convoluted portions of the body at a smaller angle relative to the sides of the tunnel. Decreased tunnel width did not affect the average forward speed during the moving phase. Hence, tread speed and tunnel width affected different kinematic variables. Significant changes in kinematics did not always cause significant changes in locomotor performance capacity.
Myocardial Oxygen Consumption and Lactate Release by the Hypoxic Hagfish Heart
Authors: Forster M. E.
Published: April 2021

Myocardial oxygen consumption and lactic acid release were measured in the isolated heart of a hagfish (Eptatretus cirrhatus Forster) perfused in vitro. Two different ranges of partial pressures of oxygen were employed ( 3.87–5.87 and 1.60–2.67kPa). All hearts released lactate into the perfusate, but the rate of release was greater and was depressed at the lower .

When energy production through the glycolytic pathway to lactate is converted to oxygen equivalents and added to measured oxygen consumption rates, over a wide range of power outputs and different values of , the data can be fitted to a single linear regression line. The rate of oxygen consumption of the hagfish myocardium, so obtained, is similar to values reported for teleost fish. The unusual ability of the hagfish myocardium to support perhaps up to 50% of its maximal power output through anaerobic metabolism is related to its extremely low cardiac energy demand.
The Heart Rate Variability Signal in Rainbow Trout (Oncorhynchus Mykiss)
Authors: Vera Luis De , Priede Imants G.
Published: April 2021

Records of heart rate often show short-term variation in beat-to-beat interval which can be plotted as a heart rate variability signal (HRVS). It has been suggested that, in mammals, analysis of the HRVS can be used as a quantitative means of investigating control of cardiac function (McDonald, 1980). An HRVS can be recognised in the electrocardiograms (ECGs) of teleost fishes (Armstrong et al. 1989a) and these signals have been recorded by telemetry from free-living fish in their natural environment (Armstrong et al. 1989b). Regulation of the heart is usually studied by blocking components of the system by surgical or pharmacological intervention or using in vitro isolated preparations (Farrel, 1984). Analysis of the HRVS may provide a unique insight into the function of the intact system and should be applicable to free-swimming fish in their natural environment.
Centrally Generated Rhythmic and Non-Rhythmic Behavioural Responses inRana TemporariaEmbryos
Authors: Soffe S. R.
Published: April 2021

Embryos of the frog Rana temporaria up to and around the time of hatching show a range of rhythmic and non-rhythmic movements. These may occur spontaneously or in response to lightly touching the skin of the trunk or head. The first response to touching one side is usually on the opposite side. Non-rhythmic movements range from weak twitches centred on the mid trunk to strong flexions along much of one side of the body and part of the tail, which result in the animal becoming tightly coiled. Rhythmic movements range from slow, high-amplitude ‘lashing’ movements to faster, lower-amplitude ‘swimming’ movements. During rhythmic movements, a wave of bending passes along the animal from head to tail. The longitudinal phase delay in bending is constant for a range of cycle periods (88–193 ms) but is not uniform along the whole body. Bending is maximal along the body and rostral part of the tail, decreases towards the tip of the tail and is lowest at the head. Lateral displacement during rhythmic movements is lowest 0.2 body lengths from the snout, increases rostral and caudal to this level and is highest at the tip of the tail.

In animals immobilised with curare, a range of patterns of motor discharge can be recorded in response to stimulation. Non-rhythmic responses range from single spikes to prolonged bursts, usually on the opposite side to the stimulus. Stronger bursts can alternate briefly between the two sides and are never synchronous on both. Episodes of sustained rhythmic activity can be evoked by touch, electrical stimulation of the skin or, rarely, dimming the lights. Cycle periods within each episode can vary considerably but often shorten as activity proceeds. Discharge on the two sides alternates (phase is approximately 0.5). Motor root burst duration correlates with cycle period, bursts being longer at longer cycle periods. Burst onset is delayed caudally, this delay being longer at longer cycle periods. Stimulating one side of the head evokes a large burst of discharge on the opposite side, often followed by sustained rhythmic discharge. These responses in immobilised animals are judged to constitute centrally generated correlates of the main behavioural responses of R. temporaria embryos.
Fibre Types in Leech Body Wall Muscle
Authors: Rowlerson A. M. , Blackshaw S. E.
Published: April 2021

The fibre type composition of obliquely striated muscle of adult Hirudo medicinalis was investigated by enzyme histochemistry, by immunohistochemistry and by SDS-PAGE. The oxidative capacity of the fibres, assessed by succinate dehydrogenase activity, was similar in all three layers of body wall muscle (longitudinal, oblique and circular) and in dorsoventral muscles. Histochemical localisation of Mg2+-activated actomyosin ATPase activity gave stronger staining in the longitudinal muscle than in other layers. As muscle shortening speed is directly related to this form of ATPase activity, this suggests that the longitudinal layer fibres are faster contracting than the circular, oblique or dorsoventral muscles. Results with polyclonal antibodies specific for vertebrate myosins were consistent with the ATPase results, i.e. fibres with the lowest actomyosin ATPase activity reacted preferentially with an antibody for a slower myosin. Thus, anti-T2, selective for vertebrate tonic fibre myosin, bound preferentially to fibres in oblique, circular and dorsoventral muscles, whereas anti-S, selective for vertebrate slow twitch fibre myosin (faster than vertebrate tonic fibre myosin), bound preferentially to the bulk of longitudinal layer fibres. Whereas most of the longitudinal layer stained uniformly with the anti-S antibody, some fibres in the outermost bundles were negative for the anti-S antibody and were, therefore, different from the main mass of longitudinal fibres. SDS-PAGE analysis of contractile protein preparations from body wall muscle also revealed a difference in the composition of the oblique, circular and dorsoventral muscles compared to the longitudinal layer, supporting the conclusion that leech body wall muscle contains two fibre types.
Development of Segment- and Target-Related Neuronal Identity in the Medicinal Leech
Authors: Jellies John , Kopp Diane M. , Bledsoe James W.
Published: April 2021

The rhythmic pumping of the paired heart tubes in the medicinal leech Hirudo medicinalis offers an excellent system for studying the development of a simple behavior in terms of its neuronal and muscular components. The present experiments examined the development of identified heart excitor (HE) motor neurons during normal embryogenesis. Using intracellular impalements and dyefilling, we found that the HE motor neurons could be identified at an early stage of development and that they initially elaborated axonal arborizations in inappropriate target fields in the ventral body wall. These inappropriate projections were retracted as those at the appropriate target (developing heart tube muscle) extended. This remodelling occurred at least 4 days before the HEs acquired the adult phenotype of being driven to fire action potentials in a rhythmic pattern. Although the HEs exhibited centrally driven rhythmic oscillations late in embryogenesis, at earlier stages they exhibited largely a tonic discharge interrupted by bursts of inhibitory potentials in a periodic, but not a rhythmic, pattern. We also found what appeared to be non-rhythmic HE homologs in anterior and posterior segments where HE neurons have not been previously described. These homologs may project along similarly patterned guidance cues early in development, since they are at first indistinguishable from the definitive HEs, but they continued to elaborate both lateral and medial body wall projections over the same period that definitive HEs were expanding their arborizations over the developing heart tube and retracting their body wall projections. In both adult and embryonic leeches the homologs exhibited mostly tonic activity that was interrupted by pronounced, but non-rhythmic, hyperpolarizing postsynaptic potentials. Thus, there appears to be early segmental specification directing the final phenotype of the iterated neuron that, in most segments, becomes the HE motor neuron.
The structure and function of the fungal V-ATPase
Authors: Stevens Tom H.
Published: April 2021

The fungal vacuole is a prominent organelle that functions as a storage site for amino acids, Ca2+, storage carbohydrates, inorganic phosphate and numerous hydrolases (Fig. 1) (Klionsky et al. 1990). A hallmark of fungal vacuoles is that they are acidic compartments involved in the turnover of cellular macromolecules. In the yeast Saccharomyces cerevisiae, the hydrolase activities in the vacuole are required for diploid cells to progress normally through sporulation and meiosis. The goal of this chapter is to present an overview of what is known about the enzyme complex responsible for acidifying the fungal vacuole and to summarize the current view of the function of acidification of the vacuolar network.
Lateral Bending During Lizard Locomotion
Authors: Ritter Dale
Published: April 2021

Lateral bending of the trunk during terrestrial, quadrupedal locomotion was analyzed in four species of lizards, using high-speed videography and computerized motion analysis. The focus of the analysis was whether lizards produce a standing or a traveling wave of bending in the trunk during locomotion. Lizards with well-developed limbs (Cnemidophorus tigris and Dipsosaurus dorsalis) exhibit a standing wave of lateral bending at low speeds, which is replaced by a traveling wave of bending as velocity increases. Lizards with diminutive limbs (Gerrhonotus kingii and Eumeces multivirgatus) exhibit a traveling wave of lateral bending, even at the lowest speeds recorded. These results are not consistent with the ideas that lizards produce a standing wave of lateral bending during locomotion or that amniote vertebrates have lost the ability to produce a traveling wave of lateral flexion due to a change in the central pattern generator that controls locomotion.
The monosynaptic connections between the serotonin-containing LP3 and RPas neurones in Helix are serotonergic
Authors: Vehovszky Ágnes , Kemenes György , S.-Rózsa Katalin
Published: April 2021

Monosynaptic connections between a giant serotonin-containing neurone and its serotonin-containing followers in the snail Helix pomatia were studied in isolated preparations of the central nervous system. The presynaptic cell was the LP3 cell in the left pedal ganglion and the followers were the RPas cells in the right parietal ganglion. The light microscopical morphology of the pre- and postsynaptic cells was investigated in whole-mount preparations following intracellular injection with a nickel-lysine complex. Axons from LP3 project towards the cerebral and suboesophageal ganglia or run in peripheral nerves which innervate feeding muscles and the foot. The follower neurones (RPas) project into nerves which innervate the heart and other visceral organs. The axons of LP3 and the RPas cells run in close proximity in the visceral ganglia. Ionophoretic application of serotonin onto the membrane of the postsynaptic RPas neurones mimicked the excitatory effect of the stimulation of the presynaptic LP3. Both the synaptic transmission between LP3 and its followers and the excitatory effect of exogenously applied serotonin on the RPas neurones decreased or were blocked in the presence of serotonin or the serotonin antagonists tryptamine, bufotenine, 7-methyltryptamine and MDL 72222-EFO2 in the bath. From this, we conclude that the excitatory neurotransmitter between LP3 and followers is serotonin and not some other neurotransmitter which might coexist with serotonin in LP3. The serotonergic monosynaptic connections between LP3 and its right parietal followers may play a role in a variety of serotonin-mediated physiological and behavioural responses, forming a link between feeding, locomotion and visceral functions.
Kidney and urinary bladder responses of freshwater rainbow trout to isosmotic NaCL and NaHCO3 infusion
Authors: Curtis B. James , Wood Chris M.
Published: April 2021

The relative roles of the kidney and urinary bladder in ion, fluid and acid-base regulation were examined in freshwater rainbow trout chronically infused with either 140 mmol I-1 NaCl or 140 mmol I-1 NaHCO3 (3mlkg-1h-1) for 32 h. NaCl had a negligible effect on blood ionic and acid-base status, whereas NaHCCh induced a metabolic alkalosis characterized by a rise in arterial pH and [HCO3-] and an equimolar fall in [Cl-]. Urine was collected via either an internal catheter, which bypassed bladder function, or an external urinary catheter, which collected naturally voided urine. As a percentage of the infusion rate, glomerular filtration rate increased by about 135%, but urine flow rate (UFR) by only 80 %, reflecting increased tubular reabsorption of H2O. During NaCl infusion, virtually all of the extra Na+ and Cl- filtered was reabsorbed by the kidney tubules, resulting in an increased UFR with largely unchanged composition. During Na HCO3- infusion, tubular Na+ and Cl- reabsorption again kept pace with filtration. HCO3- reabsorption also increased, but did not keep pace with filtration; an increased flow of HCO3--rich urine resulted, which excreted about 10% of the infused base load. At rest, fish fitted with external catheters voided in discrete bursts of about 0.85 ml kg-1 at 25 min intervals. During infusion, burst frequency increased by about 40 % and burst volume by about 20 %. Reabsorption by the bladder reduced UFR by 25 %, the excretion of Na+ and Cl - by 50 %, of K+ by 44 % and of urea by 25 %. These differences persisted on a relative basis during NaCl and NaHO3 infusion despite the decreased residence time. However, HCO3- was neither secreted nor reabsorbed by the bladder. We conclude that the freshwater kidney functions to remove as much NaCl as possible from the urine, regardless of the NaCl load, and this role is supplemented by bladder function. The bladder plays no role in acid-base regulation during metabolic alkalosis.