bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACT
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.
Effect of Brood Size Manipulation on Offspring Physiology: An Experiment with Passerine Birds
Authors: Burness Gary P. , McClelland Grant B. , Wardrop Sharilynn L. , Hochachka Peter W. 
Published: April 2021

ABSTRACT
The environment experienced during ontogeny has a significant impact on the physiological condition of offspring. This, in turn, forecasts survival probabilities and future reproductive potential. Despite the prominent role that the concept of condition plays in evolutionary studies, the physiological and biochemical characters that define it remain relatively unexplored. In this study, we quantified the impact of brood size manipulations on the physiology and biochemistry of nestling tree swallows (Tachycineta bicolor) shortly before they fledged. Over two breeding seasons, we either increased or decreased the number of individuals in a brood by a single nestling. Every 2–4 days, we determined the resting rate of oxygen consumption of individuals in each brood. Growth was followed until 16 days of age, at which time, to look for potential trade-offs in energy allocation, we measured total lipid mass, skeletal muscle and organ mass, indices of blood oxygen-carrying capacity and the activities of key metabolic enzymes in various tissues. Surprisingly, there was a minimal response of most characters to brood manipulation, suggesting that physiological and biochemical development is relatively invariant except perhaps under extreme conditions. Individuals reared in artificially enlarged broods, however., had a significantly lower body mass, body-size-adjusted , gizzard mass and total lipid mass. These individuals also had decreased activity of cardiac 3-hydroxyacyl CoA dehydrogenase, suggesting a decreased capacity for oxidation of fatty acids. How these characters affect survival or the future adult phenotype remains unknown.
The Transporter-Like Protein Inebriated Mediates Hyperosmotic Stimuli Through Intracellular Signaling
Authors: Chiu Chi-Sung , Ross Linda S. , Cohen Bruce N. , Lester Henry A. , Gill Sarjeet S. 
Published: April 2021

ABSTRACT
We cloned the inebriated homologue MasIne from Manduca sexta and expressed it in Xenopus laevis oocytes. MasIne is homologous to neurotransmitter transporters but no transport was observed with a number of putative substrates. Oocytes expressing MasIne respond to hyperosmotic stimulation by releasing intracellular Ca2+, as revealed by activation of the endogenous Ca2+-activated Cl− current. This Ca2+ release requires the N-terminal 108 amino acid residues of MasIne and occurs via the inositol trisphosphate pathway. Fusion of the N terminus to the rat γ-aminobutyric acid transporter (rGAT1) also renders rGAT1 responsive to hyperosmotic stimulation. Immunohistochemical analyses show that MasIne and Drosophila Ine have similar tissue distribution patterns, suggesting functional identity. Inebriated is expressed in tissues and cells actively involved in K+ transport, which suggests that it may have a role in ion transport, particularly of K+. We propose that stimulation of MasIne releases intracellular Ca2+ in native tissues, activating Ca2+-dependent K+ channels, and leading to K+ transport.
Novel Aspects Of The Transport Of Organic Anions By The Malpighian Tubules OfDrosophila Melanogaster
Authors: Linton Stuart M. , O’donnell M. J. 
Published: April 2021

ABSTRACTPara-aminohippuric acid (PAH) is a negatively charged organic ion that can pass across the epithelium of Malpighian tubules. Its mode of transport was studied in Malpighian tubules of Drosophila melanogaster. PAH transport was an active process, with a Km of 2.74 mmol l−1 and a Vmax of 88.8 pmol min−1. Tubules had a low passive permeability to PAH, but PAH transport rates (832 nmol min−1 mm2) and concentrative ability ([PAH]secreted fluid:[PAH]bath=81.2) were the highest measured to date for insects. Competition experiments indicated that there were two organic anion transporters, one that transports carboxylate compounds, such as PAH and fluorescein, and another that transports sulphonates, such as amaranth and Indigo Carmine. PAH transport appears to be maximal in vivo because the rate of transport by isolated tubules is not increased when these are challenged with cyclic AMP, cyclic GMP, leucokinin I or staurosporine. Basolateral PAH transport was inhibited by ouabain and dependent on the Na+ gradient. The Malpighian tubules appeared not to possess an organic acid/α-keto acid exchanger because PAH accumulation was not affected by low concentrations (100 μmol l−1) of α-keto acids (α-ketoglutarate, glutarate, citrate and succinate) or the activity of phosphokinase C. PAH transport may be directly coupled to the Na+ gradient, perhaps via Na+/organic acid cotransport. Fluorescence microscopy showed that transport of the carboxylate fluorescein was confined to the principal cells of the main (secretory) segment and all the cells of the lower (reabsorptive) segment. Organic anions were transported across the cytoplasm of the principal cells both by diffusion and in vesicles. The accumulation of punctate fluorescence in the lumen is consistent with exocytosis of the cytoplasmic vesicles. Apical PAH transport was independent of the apical membrane potential and may not occur by an electrodiffusive mechanism.
Function Of The Heterocercal Tail In White Sturgeon: Flow Visualization During Steady Swimming And Vertical Maneuvering
Authors: Liao James , Lauder George V. 
Published: April 2021

ABSTRACTBasal ray-finned fishes possess a heterocercal tail in which the dorsal lobe containing the extension of the vertebral column is longer than the ventral lobe. Clarifying the function of the heterocercal tail has proved elusive because of the difficulty of measuring the direction of force produced relative to body position in the aquatic medium. We measured the direction of force produced by the heterocercal tail of the white sturgeon (Acipenser transmontanus) by visualizing flow in the wake of the tail using digital particle image velocimetry (DPIV) while simultaneously recording body position and motion using high-speed video. To quantify tail function, we measured the vertical body velocity, the body angle and the path angle of the body from video recordings and the vortex ring axis angle and vortex jet angle from DPIV recordings of the wake downstream from the tail. These variables were measured for sturgeon exhibiting three swimming behaviors at 1.2 L s−1, where L is total body length: rising through the water column, holding vertical position, and sinking through the water column. For vertical body velocity, body angle and path angle values, all behaviors were significantly different from one another. For vortex ring axis angle and vortex jet angle, rising and holding behavior were not significantly different from each other, but both were significantly different from sinking behavior. During steady horizontal swimming, the sturgeon tail generates a lift force relative to the path of motion but no rotational moment because the reaction force passes through the center of mass. For a rising sturgeon, the tail does not produce a lift force but causes the tail to rotate ventrally in relation to the head since the reaction force passes ventral to the center of mass. While sinking, the direction of the fluid jet produced by the tail relative to the path of motion causes a lift force to be created and causes the tail to rotate dorsally in relation to the head since the reaction force passes dorsal to the center of mass. These data provide evidence that sturgeon can actively control the direction of force produced by their tail while maneuvering through the water column because the relationship between vortex jet angle and body angle is not constant.
Modulatory Effects of Nitric Oxide on Synaptic Depression in the Crayfish Neuromuscular System
Authors: Aonuma Hitoshi , Nagayama Toshiki , Takahata Masakazu 
Published: April 2021

ABSTRACT
A characteristic physiological property of the neuromuscular junction between giant motor neurones (MoGs) and fast flexor muscles in crayfish is synaptic depression, in which repetitive electrical stimulation of the MoG results in a progressive decrease in excitatory junction potential (EJP) amplitude in flexor muscle fibres. Previous studies have demonstrated that L-arginine (L-Arg) modulates neuromuscular transmission. Since L-Arg is a precursor of nitric oxide (NO), we examined the possibility that NO may be involved in modulating neuromuscular transmission from MoGs to abdominal fast flexor muscles. The effect of a NO-generating compound, NOC7, was similar to that of L-Arg, reversibly decreasing the EJP amplitude mediated by the MoG. While NOC7 reduced the amplitude of the EJP, it induced no significant change in synaptic depression. In contrast, a scavenger of free radical NO, carboxy-PTIO, and an inhibitor of nitric oxide synthase, L-NAME, reversibly increased the EJP amplitude mediated by MoGs. Synaptic depression mediated by repetitive stimulation of MoGs at 1 Hz was partially blocked by bath application of L-NAME. Bath application of a NO scavenger, a NOS inhibitor and NO-generating compounds had no significant effects on the depolarisation of the muscle fibres evoked by local application of L-glutamate.
The opposing effects on EJP amplitude of NOC7 and of carboxy-PTIO and L-NAME suggest that endogenous NO presynaptically modulates neuromuscular transmission and that it could play a prominent role at nerve terminals in eliciting MoG-mediated synaptic depression in the crayfish Procambarus clarkii.
Hearing Threshold and Frequency Discrimination in the Purely Aquatic frogXenopus Laevis (Pipidae): Measurement by Means of Conditioning
Authors: Elepfandt Andreas , Eistetter Ilse , Fleig Andrea , Günther Elke , Hainich Michaela , Hepperle Susanne , Traub Burkhardt 
Published: April 2021

ABSTRACTHearing threshold and frequency discrimination for underwater sound were measured in the clawed frog Xenopus laevis by means of conditioning. A go/no go discrimination procedure was used in which the test tone was presented concurrently with a wave on the surface of the water. The tone signalled whether or not the frog should respond to the wave. The hearing range of X. laevis was 200–4000 Hz. Similar thresholds of 92–96 dB re 1 μPa were found at 600 Hz, 1400–1800 Hz and 3200–3600 Hz. A high threshold at 1000–1300 Hz suggested that this was the frequency range between the sensitivities of the amphibian and basilar papillae. Relative frequency discrimination was approximately 5 % at 400–800 Hz, 45 % at 1000 Hz and 2.4–6 % at 1600–2500 Hz. This last range encompasses the dominant frequencies of the advertisement call of this species. High discrimination acuity at these frequencies may be used in distinguishing between calling males. The threshold for a one-third-octave bandpass noise centred at 600 Hz was 27.6 dB lower than that for a pure tone of 600 Hz, suggesting that sound intensity was integrated within this bandwidth, possibly by a critical-band mechanism.
Thyroid Hormone Concentrations In Captive And Free-Ranging West Indian Manatees (Trichechus Manatus)
Authors: Ortiz Rudy M. , Mackenzie Duncan S. , Worthy Graham A. J. 
Published: April 2021

ABSTRACT
Because thyroid hormones play a critical role in the regulation of metabolism, the low metabolic rates reported for manatees suggest that thyroid hormone concentrations in these animals may also be reduced. However, thyroid hormone concentrations have yet to be examined in manatees. The effects of captivity, diet and water salinity on plasma total triiodothyronine (tT3), total thyroxine (tT4) and free thyroxine (fT4) concentrations were assessed in adult West Indian manatees (Trichechus manatus). Free-ranging manatees exhibited significantly greater tT4 and fT4 concentrations than captive adults, regardless of diet, indicating that some aspect of a captive existence results in reduced T4 concentrations. To determine whether this reduction might be related to feeding, captive adults fed on a mixed vegetable diet were switched to a strictly sea grass diet, resulting in decreased food consumption and a decrease in body mass. However, tT4 and fT4 concentrations were significantly elevated over initial values for 19 days. This may indicate that during periods of reduced food consumption manatees activate thyroid-hormone-promoted lipolysis to meet water and energetic requirements. Alterations in water salinity for captive animals did not induce significant changes in thyroid hormone concentrations. In spite of lower metabolic rates, thyroid hormone concentrations in captive manatees were comparable with those for other terrestrial and marine mammals, suggesting that the low metabolic rate in manatees is not attributable to reduced circulating thyroid hormone concentrations.
Sound Production and Hearing in the Blue Cracker Butterfly Hamadryas Feronia (Lepidoptera, Nymphalidae) From Venezuela
Authors: Yack Jayne E. , Otero L. Daniel , Dawson Jeff W. , Surlykke Annemarie , Fullard James H. 
Published: April 2021

ABSTRACT
Certain species of Hamadryas butterflies are known to use sounds during interactions with conspecifics. We have observed the behaviour associated with sound production and report on the acoustic characteristics of these sounds and on the anatomy and physiology of the hearing organ in one species, Hamadryas feronia, from Venezuela. Our observations confirm previous reports that males of this species will take flight from their tree perch when they detect a passing conspecific (male or female) and, during the chase, produce clicking sounds. Our analyses of both hand-held males and those flying in the field show that the sounds are short (approximately 0.5 s) trains of intense (approximately 80–100 dB SPL at 10 cm) and brief (2–3 ms) double-component clicks, exhibiting a broad frequency spectrum with a peak energy around 13–15 kHz. Our preliminary results on the mechanism of sound production showed that males can produce clicks using only one wing, thus contradicting a previous hypothesis that it is a percussive mechanism. The organ of hearing is believed to be Vogel’s organ, which is located at the base of the forewing subcostal and cubital veins. Vogel’s organ consists of a thinned region of exoskeleton (the tympanum) bordered by a rigid chitinous ring; associated with its inner surface are three chordotonal sensory organs and enlarged tracheae. The largest chordotonal organ attaches to a sclerite positioned near the center of the eardrum and possesses more than 110 scolopidial units. The two smaller organs attach to the perimeter of the membrane. Extracellular recordings from the nerve branch innervating the largest chordotonal organ confirm auditory sensitivity with a threshold of 68 dB SPL at the best frequency of 1.75 kHz. Hence, the clicks with peak energy around 14 kHz are acoustically mismatched to the best frequencies of the ear. However, the clicks are broad-banded and even at 1–2 kHz, far from the peak frequency, the energy is sufficient such that the butterflies can easily hear each other at the close distances at which they interact (less than 30 cm). In H. feronia, Vogel’s organ meets the anatomical and functional criteria for being recognized as a typical insect tympanal ear.
Functional Ureogenesis in the Gobiid Fish, Mugilogobius Abei
Authors: Iwata Katsuya , Kajimura Makiko , Sakamoto Tatsuya 
Published: April 2021

ABSTRACT
To examine the transition to ureogenesis, the gobiid fish Mugilogobius abei was immersed in 2 mmol l−1 NH4HCO3 or a 15N-labelled ammonia solution [1 mmol l−1 (15NH4)2SO4, pH 8.0] for 4–8 days. When exposed to 2 mmol l−1 NH4HCO3 or 15N-labelled ammonia solution for 4 days, the rate of urea excretion increased to seven times that of the control (in 20 % synthetic sea water) and remained at this level for 4 days. The proportion of nitrogen excreted as urea reached 62 % of total nitrogen excretion (ammonia-N + urea-N). 15N-enrichment of the amide-N in glutamine in the tissues of fish exposed to 15N-labelled ammonia was virtually the same as that of ammonia-N: i.e. approximately twice that of urea-N in the excreta and the tissues. Glutamine contents and glutamine synthetase activities in the liver and muscle increased greatly following exposure to ammonia. Urea and citrulline contents in the muscle and whole body of the exposed fish increased significantly, whereas uric acid contents remained unchanged. Carbamoyl phosphate synthetase III (CPSase III) mRNA expression and CPSase III activity were detected in the muscle, skin and gill, but levels were negligible in the liver. Furthermore, all other ornithine–urea cycle (O-UC) enzymes were also detected in muscle, skin and gill. Thus, M. abei clearly shows the transition from ammoniotely to ureotely under ammonia-loading condition and is able to produce urea mainly via the O-UC operating in multiple non-hepatic tissues as a means for ammonia detoxification.
Energetics of Surface Swimming in Brandt’s Cormorants (Phalacrocorax Penicillatus Brandt)
Authors: Ancel A. , Starke L. N. , Ponganis P. J. , Dam R. Van , Kooyman G. L. 
Published: April 2021

ABSTRACT
The energy requirements of Brandt’s cormorants (Phalacrocorax penicillatus) during surface swimming were measured in birds swimming under a metabolic chamber in a water flume. From the oxygen consumption recordings, we extrapolated the metabolic rate and cost of transport at water speeds ranging from 0 to 1.3 m s−1. In still water, the birds’ mean mass-specific rate of oxygen consumption while floating at the surface was 20.2 ml O2 min−1 kg−1, 2.1 times the predicted resting metabolic rate. During stead.y-state voluntary swimming against a flow, their increased with water speed, reaching 74 ml O2 min−1 kg−1 at 1.3 m s−1, which corresponded to an increase in metabolic rate from 11 to 25 W kg−1. The cost of transport decreased with swimming velocity, approaching a minimum of 19 J kg−1 m−1 for a swimming speed of 1.3 m s−1. Surface swimming in the cormorant costs approximately 18 % less than sub-surface swimming. This confirms similar findings in tufted ducks (Aythya fuligula) and supports the hypothesis that increased energy requirements are necessary in these birds during diving to overcome buoyancy and heat loss during submergence.
Curved Flight Paths and Sideways Vision in Peregrine Falcons (Falco Peregrinus)
Authors: Tucker Vance A. , Tucker Alice E. , Akers Kathy , Enderson James H. 
Published: April 2021

ABSTRACT
When diving at prey straight ahead from great distances at high speeds, a peregrine has a conflict between vision and aerodynamics: it must turn its head approximately 40 ° to one side to see the prey with maximum visual acuity at the deep fovea of one eye, but the head in this position increases aerodynamic drag and slows the falcon down. The falcon could resolve this conflict by holding its head straight and flying along a logarithmic spiral path that keeps the line of sight of the deep fovea pointed sideways at the prey. Wild peregrines, observed with binoculars, telescopes and a tracking device, did approach prey the size of American robins (Turdus migratorius) and smaller birds from distances of up to 1500 m by holding their heads straight and flying along curved paths that resembled the logarithmic spiral.
The Cardiovascular Responses of the Red-Eared Slider (Trachemys Scripta) Acclimated to Either 22 Or 5 °C: II. Effects of Anoxia on Adrenergic and Cholinergic Control
Authors: Hicks J. M. T. , Farrell A. P. 
Published: April 2021

ABSTRACT
Cardiovascular control in cold-acclimated freshwater turtles during chronic anoxic exposure is not well understood. We tested the hypothesis that the observed bradycardia in Trachemys scripta results from increased cholinergic inhibitory tone and reduced sympathetic activity. Cardiovascular status was measured in vivo in turtles acclimated to either 22 °C or 5 °C and either acutely exposed (6 h) to anoxia at 22 °C or chronically exposed (22 days) to anoxia at 5 °C. In 22 °C-acclimated turtles, injection of the cholinergic antagonist atropine induced a significant tachycardia under both normoxic and anoxic conditions. However, in 5 °C-acclimated turtles, atropine injection had little effect on heart rate. Therefore, cholinergic control of heart rate was suppressed during cold acclimation; instead, temperature effects are more important in bringing about bradycardia, while the intrinsic effects of anoxia and acidosis are probably important during chronic anoxia. Injection of adrenaline caused a pressor response through increased systemic resistance at both acclimation temperatures. This response was blunted by acute and chronic anoxic exposure, suggesting that systemic vasomotor control was altered independently of acclimation temperature. This anoxic blunting may be related in part to the anoxia-induced increase in systemic resistance. Injection of nadolol after atropine decreased systemic cardiac output. The tonic β-adrenergic cardiac stimulation was attenuated by acute and chronic anoxic exposure. Some of this attenuation of β-adrenergic control could be attributed to the 39–40 % reduction in cell surface β-adrenoreceptor density in the ventricles of these turtles that accompanied acute and chronic anoxic exposure. In conclusion and contrary to our original hypothesis, cholinergic and adrenergic control of the cardiovascular system in turtles was attenuated under cold anoxic conditions, perhaps assisting in the depressed physiological state of these animals.