bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrodynamics, Shell Shape, Behavior and Survivorship in the Owl Limpet Lottia Gigantea
Authors: Denny Mark W. , Blanchette Carol A.
Published: April 2021

On wave-swept rocky shores, limpets are subjected to water velocities in excess of 20 m s−1, which may impose large hydrodynamic forces. Despite the extreme severity of this flow environment, predictions from conical models suggest that limpets’ shells are typically far from the optimal shape that would minimize the risk of dislodgment, a deviation that is allowed by the high tenacity of the limpets’ adhesive system. In this study, we test this conclusion using an actual limpet. The shell of Lottia gigantea differs substantially from the hydrodynamic optimum in that its apex is displaced anteriorly to form a plough, which is used to defend the limpet’s territory. The hydrodynamic effects of this shape are similar to those observed in conical models: the animal experiences an increased lift when facing into the flow and a decreased lift when the flow is at its back. However, neither effect has a substantial impact on the risk of dislodgment. When the animal is stationary, its adhesion to the substratum is very strong, and its risk of being dislodged is small regardless of its orientation to the flow and despite its sub-optimal shape. In contrast, when the animal is crawling rapidly, its adhesion is substantially decreased, and it would probably be dislodged by rapid flow even if the shell were shaped optimally. The risk of dislodgment by waves is therefore functionally independent of shell shape. In essence, despite the extremely high water velocities to which this species is subjected, its shell has had the ‘permission’ of the flow environment to respond to other selective factors, in particular those associated with its aggressive, territorial behavior. The result is a shell that is both a potent territorial weapon and a functional (albeit less than optimal) hydrodynamic shape.
Blocking and the detection of odor components in blends
Authors: Hosler Jay S. , Smith Brian H.
Published: April 2021

Recent studies of olfactory blocking have revealed that binary odorant mixtures are not always processed as though they give rise to mixture-unique configural properties. When animals are conditioned to one odorant (A) and then conditioned to a mixture of that odorant with a second (X), the ability to learn or express the association of X with reinforcement appears to be reduced relative to animals that were not preconditioned to A. A recent model of odor-based response patterns in the insect antennal lobe predicts that the strength of the blocking effect will be related to the perceptual similarity between the two odorants, i.e. greater similarity should increase the blocking effect. Here, we test that model in the honeybee Apis mellifera by first establishing a generalization matrix for three odorants and then testing for blocking between all possible combinations of them. We confirm earlier findings demonstrating the occurrence of the blocking effect in olfactory learning of compound stimuli. We show that the occurrence and the strength of the blocking effect depend on the odorants used in the experiment. In addition, we find very good agreement between our results and the model, and less agreement between our results and an alternative model recently proposed to explain the effect.
Estimation of the rate of oxygen consumption of the common eider duck (Somateria Mollissima), With some measurements of heart rate during voluntary dives
Authors: Hawkins P. A. J. , Butler P. J. , Woakes A. J. , Speakman J. R.
Published: April 2021

The relationship between heart rate (fH) and rate of oxygen consumption (V˙O2) was established for a marine diving bird, the common eider duck (Somateria mollissima), during steady-state swimming and running exercise. Both variables increased exponentially with speed during swimming and in a li.near fashion during running. Eleven linear regressions of V˙O2 (ml kg-1 min_1) on fH (beats min_1) were obtained: five by swimming and six by running the birds. The common regression was described by V˙O2=10.1+0.15 fH (r2=0.46, N=272, P<0.0001). The accuracy of this relationship for predicting mean V˙O2was determined for a group of six birds by recording fHcontinuously over a 2-day period and comparing estimated V˙O2obtained using the common regression with (i) V˙O2estimated using . the doubly labelled water technique (DLW) and (ii) V˙O2 measured using respirometry. A two-pool model produced the most accurate estimated V˙O2using DLW. Because of individual variability within mean values of V˙O2estimated using both techniques, there was no significant difference between mean V˙O2 estimated using fH or DLW and measured V˙O2values (P>0.2), although individual errors were substantially less when fH was used rather than DLW to estimate V˙O2. Both techniques are, however, only suitable for estimating mean V˙O2for a group of animals, not for individuals.

Heart rate and behaviour were monitored during a bout of 63 voluntary dives by one female bird in an indoor tank 1.7 m deep. Tachycardia occurred both in anticipation of and following each dive. Heart rate decreased before submersion but was above resting values for the whole of the dive cycle. Mean fH at mean dive duration was significantly greater than fH while swimming at maximum sustain.able surface speeds. Heart rate was used to estimate mean V˙O2 during the dive cycle and to predict aerobic dive limit (ADL) for shallow dives.
Comparative study of tongue protrusion in three iguanian lizards, Sceloporus Undulatus, Pseudotrapelus Sinaitus and Chamaeleo Jacksonii
Authors: Meyers Jay J. , Nishikawa Kiisa C.
Published: April 2021

The goal of this study was to investigate the function of the hyolingual muscles used during tongue protraction in iguanian lizards. High-speed videography and nerve-transection techniques were used to study prey capture in the iguanid Sceloporus undulatus, the agamid Pseudoptrapelus sinaitus and the chameleonid Chamaeleo jacksonii. Denervation of the mandibulohyoideus muscle slips had an effect only on P. sinaitus and C. jacksonii, in which tongue protrusion or projection distance was reduced. In C. jacksonii, denervation of the M. mandibulohyoideus completely prevented little hyoid protraction. Denervation of the M. verticalis had no effect on S. undulatus, but reduced tongue protrusion distance in P. sinaitus. Denervation of the accelerator muscle in C. jacksonii inhibited tongue projection completely. The function of the M. mandibulohyoideus and M. verticalis has become increasingly specialized in P. sinaitus and especially in C. jacksonii to allow greater tongue protrusion. The combined results of these treatments suggest that these three groups represent transitional forms, both morphologically and functionally, in the development of a projectile tongue.
The mechanics of locomotion in the squid Loligo Pealei: Locomotory function and unsteady hydrodynamics of the jet and intramantle pressure
Authors: Anderson Erik J. , Demont M. Edwin
Published: April 2021

High-speed, high-resolution digital video recordings of swimming squid (Loligo pealei) were acquired. These recordings were used to determine very accurate swimming kinematics, body deformations and mantle cavity volume. The time-varying squid profile was digitized automatically from the acquired swimming sequences. Mantle cavity volume flow rates were determined under the assumption of axisymmetry and the condition of incompressibility. The data were then used to calculate jet velocity, jet thrust and intramantle pressure, including unsteady effects. Because of the accurate measurements of volume flow rate, the standard use of estimated discharge coefficients was avoided. Equations for jet and whole-cycle propulsive efficiency were developed, including a general equation incorporating unsteady effects.

Squid were observed to eject up to 94% of their intramantle working fluid at relatively high swimming speeds. As a result, the standard use of the so-called large-reservoir approximation in the determination of intramantle pressure by the Bernoulli equation leads to significant errors in calculating intramantle pressure from jet velocity and vice versa. The failure of this approximation in squid locomotion also implies that pressure variation throughout the mantle cannot be ignored. In addition, the unsteady terms of the Bernoulli equation and the momentum equation proved to be significant to the determination of intramantle pressure and jet thrust. Equations of propulsive efficiency derived for squid did not resemble Froude efficiency. Instead, they resembled the equation of rocket motor propulsive efficiency. The Froude equation was found to underestimate the propulsive efficiency of the jet period of the squid locomotory cycle and to overestimate whole-cycle propulsive efficiency when compared with efficiencies calculated from equations derived with the squid locomotory apparatus in mind. The equations for squid propulsive efficiency reveal that the refill period of squid plays a greater role, and the jet period a lesser role, in the low whole-cycle efficiencies predicted in squid and similar jet-propelled organisms. These findings offer new perspectives on locomotory hydrodynamics, intramantle pressure measurements and functional morphology with regard to squid and other jet-propelled organisms.
The Hind Wing of the Desert Locust (Schistocerca Gregaria Forskål): II. Mechanical Properties and Functioning of the Membrane
Authors: Smith C. W. , Herbert R. , Wootton R. J. , Evans K. E.
Published: April 2021

As part of an investigation of the functional mechanics of the hind wing of the desert locust Schistocerca gregaria, the Young’s modulus of the membrane was measured using a newly developed universal materials test machine capable of testing very small specimens of cuticle, down to 1 mm gauge length. Strain was measured optically. Specimens were cut from various locations around the wing and tested under controlled temperature and humidity. The modulus of the membrane was typically between 1 and 5 GPa, but both this and the membrane thickness varied around the wing, with the remigium and the anal fan showing markedly different properties. The membrane was tested for chitin using two methods: a gas pyrolysis/mass spectrometry assay, and a gold-labelled immunoassay specific to chitin. None was detected, and the membrane may consist of epicuticle alone. The wings were examined for evidence of crystalline material using standard polarising microscopy and an advanced technique that distinguishes between three components of the polarised image. Birefringence was detected in the membrane of the anterior part of the wing, but vanished when the membrane was separated from the surrounding veins, suggesting that it was due to pre-stress rather than to ultrastructure. The implications are discussed.
The Hind Wing of the Desert Locust (Schistocerca Gregaria Forskål): III. A Finite Element Analysis of a Deployable Structure
Authors: Herbert R. C. , Young P. G. , Smith C. W. , Wootton R. J. , Evans K. E.
Published: April 2021

Finite element analysis is used to model the automatic cambering of the locust hind wing during promotion: the umbrella effect. It was found that the model required a high degree of sophistication before replicating the deformations found in vivo. The model has been validated using experimental data and the deformations recorded both in vivo and ex vivo. It predicts that even slight modifications to the geometrical description used can lead to significant changes in the deformations observed in the anal fan. The model agrees with experimental data and produces deformations very close to those seen in free-flying locusts. The validated model may be used to investigate the varying geometries found in orthopteran anal fans and the stresses found throughout the wing when loaded.
Characterisation of the H+/Peptide Cotransporter of eel Intestinal Brush-Border Membranes
Authors: Verri Tiziano , Maffia Michele , Danieli Antonio , Herget Martina , Wenzel Uwe , Daniel Hannelore , Storelli Carlo
Published: April 2021

H+/peptide cotransport in brush-border membrane vesicles (BBMVs) from eel (Anguilla anguilla) intestine was studied by measuring D-[3H]-phenylalanyl-L-alanine uptake and by monitoring peptide-dependent intravesicular acidification using the pH-sensitive dye Acridine Orange. D-[3H]-phenylalanyl-L-alanine influx was greatly stimulated by an inside-negative membrane potential and enhanced by an inwardly directed H+ gradient. In parallel, vesicular H+ influx was significantly increased in the presence of extravesicular D-phenylalanyl-L-alanine or a series of glycyl and L-prolyl peptides. H+/peptide cotransport displayed saturable kinetics involving a single carrier system with apparent substrate affinities of 0.9–2.6 mmol l−1 depending on the particular peptide. All substrates tested competed with this system.

Pre-incubation of BBMVs with dipeptides prevented diethylpyrocarbonate inhibition of transport activity, suggesting that the substrates mask histidine residues involved in the catalytic function of the transporter. Using human PepT1-specific primers, a reverse transcription–polymerase chain reaction (RT-PCR) signal was detected in eel intestine. Our results suggest that, in eel intestine, a brush-border membrane ‘low-affinity’-type H+/peptide cotransport system is present that shares kinetic features with the mammalian intestinal PepT1-type transporters.
Improvement in the Efficiency of Oxidative Phosphorylation in the Freshwater eel Acclimated to 10.1 MPa Hydrostatic Pressure
Authors: Theron Michaël , Guerrero François , Sébert Philippe
Published: April 2021

Previous studies have suggested that the efficiency of oxidative phosphorylation in the freshwater eel (Anguilla anguilla) is increased after acclimation to high hydrostatic pressure. Analysis at atmospheric pressure of the respiratory chain complexes showed that, after 21 days at 10.1 MPa, the activity of complex II was decreased to approximately 50 % (P<0.01) of the control value and that cytochrome c oxidase (complex IV) activity was significantly increased to 149 % of the control value (P<0.05). ADP/O ratios calculated from mitochondrial respiration measurements were significantly increased after acclimation to high hydrostatic pressure (2.87 versus 2.52, P<0.001) when measured in the presence of pyruvate plus malate at atmospheric pressure. These results clearly show an increased oxidative phosphorylation efficiency in response to high-pressure acclimation.
Hydrodynamics of Unsteady Fish Swimming and the Effects of Body Size: Comparing the Flow Fields of Fish Larvae and Adults
Authors: Müller U. K. , Stamhuis E. J. , Videler J. J.
Published: April 2021

Zebra danios (Brachydanio rerio) swim in a burst-and-coast mode. Most swimming bouts consist of a single tail flick and a coasting phase, during which the fish keeps its body straight. When visualising the flow in a horizontal section through the wake, the effects of the flow regime become apparent in the structure of the wake. In a two-dimensional, medio-frontal view of the flow, larvae and adults shed two vortices at the tail during the burst phase. These vortices resemble a cross section through a large-core vortex ring: two vortex cores packed close together with the central flow directed away from the fish. This flow pattern can be observed in larvae (body length approximately 4 mm) at Reynolds numbers below 100 as well as in adult fish (body length approximately 35 mm) at Reynolds numbers above 1000. Larval vortices differ from those of adult zebra danios mainly in their relatively wider vortex cores (higher ratio of core radius to ring radius) and their lower vortex circulation. Both effects result from the increased importance of viscosity on larval flows. During the coasting phase, larval and adult flows again differ because of the changing importance of viscosity. The high viscosity of the water causes large vortical flows adjacent to the larva”s body. These regions of high vorticity represent the huge body of water dragged along by the larva, and they cause the larva to stop almost immediately after thrust generation ceases. No such areas of high vorticity are visible adjacent to adult zebra danios performing a comparable swimming manoeuvre. The rapid decrease in vortex circulation and the severe reduction in the coasting distance due to viscous drag contribute to the high cost that larvae – unlike adult fish – face when using a burst-and-coast swimming style.
Na+ and Ca2+ Pumps in the Gills, Epipodites and Branchiostegites of the European Lobster Homarus Gammarus: Effects of Dilute Sea Water
Authors: Flik Gert , Haond Christophe
Published: April 2021

Crude homogenates and plasma-membrane-enriched fractions were prepared from the epithelium of the gills, epipodites and branchiostegites of intermoult European lobsters Homarus gammarus, and Na+/K+-ATPase, Ca2+-ATPase and Na+/Ca2+ exchange activities were quantified in these tissues. Lobsters were kept in sea water (salinity 35 ‰) or were adapted to dilute sea water (22.1 ‰). The lobster hyperregulates haemolymph osmolarity and Ca2+ levels in both media. Homogenates of the podobranchs, arthrobranchs and pleurobranchs had comparable Na+/K+-ATPase specific activities, and mean activities increased significantly for all three types of gills when the animals were kept in dilute sea water. In the epipodites and branchiostegites, Na+/K+-ATPase specific activities exceeded those in the gills, and exposure to dilute sea water greatly enhanced these activities. In sea water, 80 % of the total Na+/K+-ATPase activity is associated with the gills and epipodites (each tissue containing 40 %) and 20 % with the branchiostegites; in dilute sea water, the gills contained approximately 25 %, the epipodites 40 % and the branchiostegites approximately 35 % of the total activity, indicating the relative importance of the epipodites and branchiostegites for ionic hyperregulation in dilute media. In plasma membrane vesicles isolated from the gills, epipodites and branchiostegites, Ca2+ transport driven by ATP and by a Na+ gradient was demonstrated. Exposure to dilute sea water enhanced Na+/Ca2+ exchange and Ca2+-ATPase activities in the epipodites and branchiostegites; in the gills, however, Ca2+ transport activities decreased. The role of these tissues and enzymes in Na+ and Ca2+ handling by the lobster is discussed.
Time of Contact and Step Length: the Effect of Limb Length, Running Speed, Load Carrying and Incline
Authors: Hoyt Donald F. , Wickler Steven J. , Cogger Edward A.
Published: April 2021

Using published values for twelve species of birds and mammals, we investigated the effects of limb length and running speed on time of contact and step length. In addition, we measured the time of contact in horses trotting up a 10 % incline and when carrying a load averaging 19 % of their body mass. From these values, we calculated stride period and step length. Our analysis of the interspecific data yielded the following relationship between time of contact (tc in s) and leg length (L in m) and running speed (v in m s−1): tc=0.80L0.84/v0.87 (r2=0.97). Both exponents in this relationship are significantly different from 1.0, indicating that step length increases with speed and that small species use a step length that, relative to their leg length, is longer than the relative step length used by larger species. Time of contact increased when a horse carried a load but not when it trotted up an incline.
Phenotypic Effects of Leptin in an Ectotherm: A New Tool to Study the Evolution of Life Histories and Endothermy?
Authors: Niewiarowski Peter H. , Balk Michelle L. , Londraville Richard L.
Published: April 2021

Leptin is a hormone that regulates energy expenditure and body mass in mammals, and it has attracted considerable attention because of its potential in treating human obesity. Comprehensive data from both pathological and non-pathological systems strongly support a role for leptin in regulating energy metabolism, in thermoregulation and in regulating the onset of puberty. We report here that daily injections of recombinant murine leptin in fence lizards (Sceloporus undulatus) produce phenotypic effects similar to those observed when leptin injections are given to mice. Lizards injected with leptin had body temperatures 0.6 °C higher, ate 30 % less food and showed a 14 % reduction in activity rates, and females showed a 2.5-fold increase in resting metabolic rates, compared with lizards injected with vehicle only (phosphate-buffered saline). We also detected native lizard leptin using an immunoassay. Our results indicate that leptin is expressed in ectotherms and may be conserved both functionally and structurally. In the wake of unprecedented research activity on the role of leptin as a cause of, and potential treatment for, human obesity, we believe that other applications of leptin research have been ignored. For example, the response of lizards to leptin injection in our study has important implications for two broad areas of research in evolutionary biology: the evolution of age at first reproduction and of endothermy. We argue that research in these areas, previously limited to comparative approaches, may now benefit from experimental manipulations using leptin.
Induction of Carbamoyl Phosphate Synthetase III and Glutamine Synthetase mRNA During Confinement Stress in Gulf Toadfish (Opsanus Beta)
Authors: Kong Haiyan , Kahatapitiya Natalie , Kingsley Kyle , Salo Wilmar L. , Anderson Paul M. , Wang Yuxiang S. , Walsh Patrick J.
Published: April 2021

Gulf toadfish (Opsanus beta) rapidly switch to excretion of urea as their main nitrogenous waste product under several laboratory conditions, including confinement to small volumes of water. Prior evidence suggested that the activities of two key enzymes of urea synthesis exhibited potentially different modes of upregulation during this switch, with carbamoyl phosphate synthethase III (CPSase III) activated allosterically by N-acetylglutamate, and glutamine synthetase (GSase) activated by increases in the concentration of protein. The present study was undertaken to examine additional aspects of the regulation of these enzymes. The sequence for O. beta CPSase III cDNA was obtained, and it was found to be similar to that of other piscine CPSases. The sequence also allowed us to develop riboprobes for CPSase III mRNA analysis using ribonuclease protection assays (RPAs). CPSase III mRNA was expressed in liver, muscle, kidney and intestine, in agreement with prior enzymatic measurements. Levels of CPSase III mRNA increased five-to tenfold (relative to β-actin mRNA) in liver (but not muscle) following 48 h of confinement stress. Measured by western analysis using an antibody to chicken GSase, confined O. beta GSase protein concentrations increased eightfold over control levels, in agreement with prior and present measurements of increases in GSase activity. Furthermore, RPAs of GSase mRNA levels demonstrated an increase of fivefold during confinement.
Aerobic and Anaerobic Swimming Performance of Individual Atlantic Cod
Authors: Reidy S. P. , Kerr S. R. , Nelson J. A.
Published: April 2021

Individual Atlantic cod (Gadus morhua) were exercised using three different measures of swimming performance. (1) An endurance test (critical swimming speed, Ucrit, protocol) designed to assess predominantly aerobic endurance swimming (duration hours). (2) An acceleration test (Uburst), in which the fish were required to swim against a rapidly increasing current until exhausted (duration minutes). This test was designed to assess predominantly glycolytic-based swimming capacity. (3) A sprint test that examined the animals’ ability to swim away from a sudden stimulus (duration seconds). Rates of oxygen consumption during the endurance test and various morphological variables of the individual fish were also measured. Both aerobic and anaerobic swimming performance of individual cod were found to be significantly repeatable over a 3 month period. during the Ucrit protocol was also significantly repeatable at intermediate to high swimming speeds, but not at low speeds. Our results support extrapolation from metabolic rates at incremented swimming speeds to zero activity as the best way to measure standard metabolic rate in cod. While performance in the Ucrit test and the sprint test were positively correlated, there was a negative correlation between performance in the Ucrit test and performance in the Uburst test. This implies a potential trade-off in individual cod between stamina and the ability to use glycolytic-based locomotion. Inter-individual variation in swimming performance during these protocols, while substantial, was not correlated with individual variation in fin surface areas, age or morphology. However, Uburst performance was dependent upon the sex of the animals, while performance during the Ucrit protocol was significantly correlated with their aerobic scope for activity.
Integrated Physiological Responses to Feeding in the Blue Crab Callinectes Sapidus
Authors: Mcgaw I. J. , Reiber C. L.
Published: April 2021

The passage of a barium meal (15 % by mass) was followed through the digestive system of the blue crab Callinectes sapidus by flash-freezing crabs at set intervals, followed by radiography of specimens. Food moved from the oesophagus into the stomach region within 15 min. After 1–2 h, food was visible in the midgut, at 6 h it had reached the hindgut, and material was still present in the stomach at this time. The stomach was emptied between 8 and 10 h after feeding, and the entire digestive system was cleared of material after 18 h. A pulsed-Doppler flowmeter was used to monitor cardiac variables and arterial haemolymph flows during a 4 h control and 24 h postprandial period. Heart rate increased immediately upon food detection and remained elevated for 16–18 h after food ingestion. There was no significant change in stroke volume of the heart, and total cardiac output increased significantly and remained elevated above pre-feeding levels for 24 h after feeding. There was no change in haemolymph flow through the anterior or posterior aorta, but flow increased in the sternal, anterolateral and hepatic arteries. These changes in haemolymph flow reflected the use of the chelae and mouthparts in feeding, contraction of the visceral muscle surrounding the gut system and mobilisation of enzymes from the hepatopancreas. There was also a postprandial increase in the rate of oxygen uptake (apparent specific dynamic action). The rate of oxygen consumption reached maximal levels 4 h after feeding and decreased slowly thereafter, reflecting the increased use of oxygen in digestion and absorption.
Factors Affecting Membrane Permeability and Ionic Homeostasis in the Cold-Submerged Frog
Authors: Donohoe Paul H. , West Timothy G. , Boutilier Robert G.
Published: April 2021

Frogs (Rana temporaria) were submerged at 3 °C in either normoxic or hypoxic water for up to 16 weeks, and denied air access, to mimic the conditions of an ice-covered pond during the winter. The activity of the skeletal muscle Na+/K+ pump over the first 2 months of hibernation, measured by ouabain-inhibitable 22Na+ efflux, was reduced by 30 % during normoxia and by up to 50 % during hypoxia. The reduction in Na+/K+ pump activity was accompanied by reductions in passive 22Na+ influx and 86Rb+ efflux (effectively K+ efflux) across the sarcolemma. This may be due to a decreased Na+ permeability of the sarcolemma and a 75 % reduction in K+ leak mediated by ATP-sensitive K+ channels (‘KATP’ channels). The lowered rates of 22Na+ and 86Rb+ flux are coincident with lowered transmembrane ion gradients for [Na+] and [K+], which may also lower Na+/K+ pump activity. The dilution of extracellular [Na+] and intracellular [K+] may be partially explained by increased water retention by the whole animal, although measurements of skeletal muscle fluid compartments using 3H-labelled inulin suggested that the reduced ion gradients represented a new steady state for skeletal muscle. Conversely, intracellular ion homeostasis within ventricular muscle was maintained at pre-submergence levels, despite a significant increase in tissue water content, with the exception of the hypoxic frogs following 4 months of submergence. Both ventricular muscles and skeletal muscles maintained resting membrane potential at pre-submergence levels throughout the entire period of hibernation. The ability of the skeletal muscle to maintain its resting membrane potential, coincident with decreased Na+/K+ pump activity and lowered membrane permeability, provided evidence of functional channel arrest as an energy-sparing strategy during hibernation in the cold-submerged frog.
The Influence of Salinity and Temperature Change on the Functioning of the Urinary Bladder in the Early Larval Stages of the Atlantic Herring Clupea Harengus L.
Authors: Tytler P. , Ireland J.
Published: April 2021

Major changes in the morphology of the urinary bladder were observed during the transition from yolk-sac to feeding larval stages of herring, in particular bladder volume increased almost sixfold. Initially, the urine flowed into the hindgut, but within days of hatching a separate urinary duct, leading to the exterior, had formed. Micturation was intermittent but quite regular. The period between micturations increased from 1.6 to 4 min in the progression between the two larval stages. The discharge volume was approximately 50 % of the full bladder volume in all stages studied. Urine flow rate (UFR) in sea water rose slightly from 1 to 1.7 nl mg−1 h−1 during early larval development. Exposure to low salinities significantly reduced UFR in yolk-sac larvae, but in the later stages UFR increased significantly in hypo-osmotic salinities, so that UFR in 4 ‰ salinity was 2.5 times that in 34 ‰ salinity. The main variable influencing UFR was discharge frequency. Cardiac output was not influenced by salinity and was considered not to be a controlling factor in the UFR response to salinity change. UFR increased with temperature with Q10 of 2.3 in stage 1 larvae and 1.5 in stage 2 larvae, over 7–15 °C.
Swimming Kinematics of Juvenile Kawakawa Tuna (Euthynnus Affinis) and Chub Mackerel (Scomber Japonicus)
Authors: Donley Jeanine M. , Dickson Kathryn A.
Published: April 2021

The swimming kinematics of two active pelagic fishes from the family Scombridae were compared to test the hypothesis that the kawakawa tuna (Euthynnus affinis) uses the thunniform mode of locomotion, in which the body is held more rigid and undergoes less lateral movement in comparison with the chub mackerel (Scomber japonicus), which uses the carangiform swimming mode. This study, the first quantitative kinematic comparison of size-matched scombrids, confirmed significantly different swimming kinematics in the two species. Ten kawakawa (15.1–25.5 cm fork length, FL) and eight chub mackerel (14.0–23.4 cm FL), all juveniles, were videotaped at 120 Hz while swimming at several speeds up to their maximum sustained speed at 24 °C. Computerized motion analysis was used to digitize specific points on the body in sequential video frames, and kinematic variables were quantified from the progression of the points over time. At a given speed, kawakawa displayed a significantly greater tailbeat frequency, but lower stride length, tailbeat amplitude and propulsive wavelength, than chub mackerel when size effects were accounted for. Midline curvatures subdivided on the basis of X-rays into individual vertebral elements were used to quantify axial bending in a subset of the fish studied. Maximum intervertebral lateral displacement and intervertebral flexion angles were significantly lower along most of the body in kawakawa than in chub mackerel, indicating that the kawakawa undergoes less axial flexion than does the chub mackerel, resulting in lower tailbeat amplitudes. However, lateral movement at the tip of the snout, or yaw, did not differ significantly interspecifically. Despite these differences, the net cost of transport was the same in the two species, and the total cost was higher in the kawakawa, indicating that the tuna juveniles are not more efficient swimmers.
Aerodynamic Characteristics of Dragonfly Wing Sections Compared with Technical Aerofoils
Authors: Kesel Antonia B.
Published: April 2021

During gliding, dragonfly wings can be interpreted as acting as ultra-light aerofoils which, for static reasons, have a well-defined cross-sectional corrugation. This corrugation forms profile valleys in which rotating vortices develop. The cross-sectional configuration varies greatly along the longitudinal axis of the wing. This produces different local aerodynamic characteristics. Analyses of the CL/CD characteristics, where CL and CD are the lift and drag coefficients, respectively (at Reynolds numbers Re of 7880 and 10 000), using a force balance system, have shown that all cross-sectional geometries have very low drag coefficients (CD,min<0.06) closely resembling those of flat plates. However, the wing profiles, depending upon their position along the span length, attain much higher lift values than flat plates. The orientation of the leading edge does not play an important role. The detectable lift forces can be compared with those of technical wing profiles for low Re numbers. Pressure measurements (at Re=9300) show that, because of rotating vortices along the chord length, not only is the effective profile form changed, but the pressure relationship on the profile is also changed. Irrespective of the side of the profile, negative pressure is produced in the profile valleys, and net negative pressure on the upper side of the profile is reached only at angles of attack greater than 0 °. These results demonstrate the importance of careful geometrical synchronisation as an answer to the static and aerodynamic demands placed upon the ultra-light aerofoils of a dragonfly.
Ventilatory and Metabolic Responses to Hypoxia and Sulphide in the Lugworm Arenicola Marina (L.)
Authors: Wohlgemuth Stephanie E. , Taylor Alan C. , Grieshaber Manfred K.
Published: April 2021

We examined the effects of hypoxia and sulphide levels on the ventilatory activity of Arenicola marina and determined whether ventilation compensates for oxygen deficiency and affects the mode of energy provision. A. marina ventilated intermittently, irrespective of ambient and sulphide concentration. The ventilation rate was 28.5±16 ml h−1 g−1 wet mass during normoxia, but increased to 175±60 % of this value during moderate hypoxia, during which aerobic energy metabolism was maintained. Below a of 6.2 kPa, A. marina reduced the ventilated volume to 54±16 % of the normoxic value and became anaerobic, as indicated by the accumulation of succinate and strombine. Incubation with 27 μmol l−1 ambient sulphide had no effect on the normoxic and hypoxic ventilation rates or on the below which anaerobiosis started (PcM). Increased sulphide concentrations reduced the ventilation rate and shifted the PcM towards a higher below 10.7 kPa. Sulphide diffused into the body and was at least partially detoxified to thiosulphate when oxygen was present. Under normoxia, sulphide accumulated in the body wall tissue and coelomic fluid when ambient sulphide levels exceeded 117 μmol l−1 and 216 μmol l−1, respectively. A decrease in in the presence of 27 or 117 μmol l−1 ambient sulphide had no significant effect on sulphide accumulation.
The Mechanisms of Urea Transport by Early Life Stages of Rainbow Trout (Oncorhynchus Mykiss)
Authors: Pilley C. M. , Wright P. A.
Published: April 2021

We tested the hypothesis that urea transport in rainbow trout (Oncorhynchus mykiss) embryos is dependent, in part, on a bidirectional urea-transport protein. Acute exposure to phloretin and urea analogs [acetamide, thiourea, 1,(4-nitrophenyl)-2-thiourea] reversibly inhibited urea excretion from the embryos to the external water. Unidirectional urea influx was inhibited by acetamide and thiourea, with IC50 values of 0.04 and 0.05 mmol l−1, respectively. Influx of urea from the external water to the embryo tended to saturate at elevated external urea concentrations (Vmax=10.50 nmol g−1 h−1 ; Km=2 mmol l−1 ). At very high urea concentrations (20 mmol l−1 ), however, a second, non-saturable component was apparent. These results indicate that urea excretion in trout embryos is dependent, in part, on a phloretin-sensitive facilitated urea transporter similar to that reported in mammalian inner medullary collecting ducts and elasmobranch kidney.
Neuroethology of the Katydid T-Cell: I. Tuning and Responses to Pure Tones
Authors: Faure Paul A. , Hoy Ronald R.
Published: April 2021

The tuning and pure-tone physiology of the T-cell prothoracic auditory interneuron were investigated in the nocturnal katydid Neoconocephalus ensiger. The T-cell is extremely sensitive and broadly tuned, particularly to high-frequency ultrasound (?:20 kHz). Adult thresholds were lowest and showed their least variability for frequencies ranging from 25 to 80 kHz. The average best threshold of the T-cell in N. ensiger ranged from 28 to 38 dB SPL and the best frequency from 20 to 27 kHz. In females, the T-cell is slightly more sensitive to the range of frequencies encompassing the spectrum of male song. Tuning of the T-cell in non-volant nymphs was comparable with that of adults, and this precocious ultrasound sensitivity supports the view that it has a role in the detection of terrestrial sources of predaceous ultrasound. In adults, T-cell tuning is narrower than that of the whole auditory (tympanic) organ, but only at audio frequencies. Superthreshold physiological experiments revealed that T-cell responses were ultrasound-biased, with intensity/response functions steeper and spike latencies shorter at 20, 30 and 40 kHz than at 5, 10 and 15 kHz. The same was also true for T-cell stimulation at 90 ° compared with stimulation at 0 ° within a frequency, which supports early T-cell research showing that excitation of the contralateral ear inhibits ipsilateral T-cell responses. In a temporal summation experiment, the integration time of the T-cell at 40 kHz (integration time constant τ=6.1 ms) was less than half that measured at 15 kHz (τ=15.0 ms). Moreover, T-cell spiking in response to short-duration pure-tone trains mimicking calling conspecifics (15 kHz) and bat echolocation hunting sequences (40 kHz) revealed that temporal pattern-copying was superior for ultrasonic stimulation. Apparently, T-cell responses are reduced or inhibited by stimulation with audio frequencies, which leads to the prediction that the T-cell will encode conspecific song less well than bat-like frequency-modulated sweeps during acoustic playback. The fact that the T-cell is one of the most sensitive ultrasound neurons in tympanate insects is most consistent with it serving an alarm, warning or escape function in both volant and non-volant katydids (nymphs and adults).
The Mechanics of Prey Prehension in Chameleons
Authors: Herrel Anthony , Meyers Jay J. , Aerts Peter , Nishikawa Kiisa C.
Published: April 2021

Iguanian lizards generally use their tongue to capture prey. Because lingual prehension is based on surface phenomena (wet adhesion, interlocking), the maximal prey size that can be captured is small. However, published records show that prey items eaten by chameleons include small vertebrates such as lizards and birds, indicating that these lizards are using a different prey prehension mechanism. Using high-speed video recordings, cineradiography, electromyography, nerve transection and stimulation experiments, we investigated the function of the tongue during prey capture. The results of these experiments indicate that chameleons have modified the primitive iguanian system by including a suction component in their prehension mechanism. Suction is generated by the activity of two modified intrinsic tongue muscles that pull the tongue pad inwards. Moreover, we demonstrate that the mechanism described here is a prerequisite for successful feeding.
Respiration and Heart Rate at the Surface Between Dives in Northern Elephant Seals
Authors: Boeuf B. J. Le , Crocker D. E. , Grayson J. , Gedamke J. , Webb P. M. , Blackwell S. B. , Costa D. P.
Published: April 2021

All underwater activities of diving mammals are constrained by the need for surface gas exchange. Our aim was to measure respiratory rate (fB) and heart rate (fH) at the surface between dives in free-ranging northern elephant seals Mirounga angustirostris. We recorded fB and fH acoustically in six translocated juveniles, 1.8–2.4 years old, and three migrating adult males from the rookery at Año Nuevo, California, USA. To each seal, we attached a diving instrument to record the diving pattern, a satellite tag to track movements and location, a digital audio tape recorder or acoustic datalogger with an external hydrophone to record the sounds of respiration and fH at the surface, and a VHF transmitter to facilitate recovery. During surface intervals averaging 2.2±0.4 min, adult males breathed a mean of 32.7±5.4 times at a rate of 15.3±1.8 breaths min−1 (means ± S.D., N=57). Mean fH at the surface was 84±3 beats min−1. The fB of juveniles was 26 % faster than that of adult males, averaging 19.2±2.2 breaths min−1 for a mean total of 41.2±5.0 breaths during surface intervals lasting 2.6±0.31 min. Mean fH at the surface was 106±3 beats min−1. fB and fH did not change significantly over the course of surface intervals. Surface fB and fH were not clearly associated with levels of exertion, such as rapid horizontal transit or apparent foraging, or with measures of immediately previous or subsequent diving performance, such as diving duration, diving depth or swimming speed. Together, surface respiration rate and the duration of the preceding dive were significant predictors of surface interval duration. This implies that elephant seals minimize surface time spent loading oxygen depending on rates of oxygen uptake and previous depletion of stores.
Detection of Bright and Dim Colours by Honeybees
Authors: Ibarra Natalie Hempel De , Vorobyev Misha , Brandt Robert , Giurfa Martin
Published: April 2021

Honeybees, Apis mellifera, were trained to detect coloured disks with either a strong or a weak intensity difference against the background. Green, blue, ultraviolet-reflecting white and grey papers were reciprocally combined as targets or backgrounds, providing strong chromatic and/or achromatic cues. The behavioural performance of the honeybees was always symmetrical for both reciprocal target/background combinations of a colour pair, thus showing that target detection is independent of whether the colour is presented as a background or as a target in combination with the other colour. Bright targets against dim backgrounds and vice versa were detected more reliably than dim target/background combinations. This result favours the general assumption that the detectability of a coloured stimulus increases with increasing intensity.
Effects of Body Size on Take-off Flight Performance in the Phasianidae (Aves)
Authors: Tobalske Bret W. , Dial Kenneth P.
Published: April 2021

To evaluate the mechanisms responsible for relationships between body mass and maximum take-off performance in birds, we studied four species in the Phasianidae: northern bobwhite (Colinus virginianus), chukar (Alectoris chukar), ring-necked pheasant (Phasianus colchicus) and wild turkey (Meleagris gallopavo). These species vary in body mass from 0.2 to 5.3 kg, and they use flight almost solely to escape predators. During take-off, all the species used a similar wingbeat style that appeared to be a vortex-ring gait with a tip reversal during the upstroke. The tip reversal is unusual for birds with rounded wings; it may offer an aerodynamic advantage during rapid acceleration. Flight anatomy generally scaled geometrically, except for average wing chord and wing area, which increased more than expected as body mass (m) increased. Pectoralis strain varied from 19.1 to 35.2 % and scaled in proportion to m0.23. This positive scaling is not consistent with the widely held assumption that muscle strain is independent of body mass among geometrically similar species. The anatomy of the species precluded measurements of in vivo pectoralis force using the strain-gauge technique that has been employed successfully in other bird species, so we could not directly test in vivo pectoralis force–velocity relationships. However, whole-body kinematics revealed that take-off power (Pta), the excess power available for climbing and accelerating in flight, scaled in proportion to m0.75 and that pectoralis mass-specific Pta decreased in proportion to m−0.26 and was directly proportional to wingbeat frequency. These trends suggest that mass-specific pectoralis work did not vary with body mass and that pectoralis stress and strain were inversely proportional, as expected from classical force–velocity models for skeletal muscle. Our observations of Pta were consistent with evidence from other species engaged in escape flight and, therefore, appear to contradict evidence from studies of take-off or hovering with an added payload.
Seasonal Changes in Physiology and Development of Cold Hardiness in the Hatchling Painted Turtle Chrysemys Picta
Authors: Costanzo Jon P. , Litzgus Jacqueline D. , Iverson John B. , E. Lee Richard
Published: April 2021

Hatchling painted turtles (Chrysemys picta) commonly hibernate in shallow, natal nests where winter temperatures may fall below −10 °C. Although hatchlings are moderately freeze-tolerant, they apparently rely on supercooling to survive exposure to severe cold. We investigated seasonal changes in physiology and in the development of supercooling capacity and resistance to inoculative freezing in hatchling Chrysemys picta exposed in the laboratory to temperatures that decreased from 22 to 4 °C over a 5.5 month period. For comparison, we also studied hatchling snapping turtles (Chelydra serpentina), a less cold-hardy species that usually overwinters under water. Although Chrysemys picta and Chelydra serpentina differed in some physiological responses, both species lost dry mass, catabolized lipid and tended to gain body water during the acclimation regimen. Recently hatched, 22 °C-acclimated Chrysemys picta supercooled only modestly (mean temperature of crystallization —6.3±0.2 °C; N=6) and were susceptible to inoculation by ice nuclei in a frozen substratum (mean temperature of crystallization —1.1±0.1 °C; N=6) (means ± s.e.m.). In contrast, cold-acclimated turtles exhibited pronounced capacities for supercooling and resistance to inoculative freezing. The development of cold hardiness reflected the elimination or deactivation of potent endogenous ice nuclei and an elevation of blood osmolality that was due primarily to the retention of urea, but was not associated with accumulation of the polyols, sugars or amino acids commonly found in the cryoprotection systems of other animals. Also, Chrysemys picta (and Chelydra serpentina) lacked both antifreeze proteins and ice-nucleating proteins, which are used by some animals to promote supercooling and to initiate freezing at the high temperatures conducive to freezing survival, respectively.