bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Significance of Fur Structure for Solar Heat Gain in the Rock Squirrel,Spermophilus Variegatus
Authors: Walsberg Glenn E. 
Published: April 2021

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTMetabolic 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

ABSTRACTVestibular 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

ABSTRACTThe 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

ABSTRACT
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+&lt; Na+&lt; Cs+&lt; 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

ABSTRACTMeasurements 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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTTo 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

ABSTRACT
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

ABSTRACTWe 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

ABSTRACT
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.