bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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&lt;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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.