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James W. Hicks - One of the best experts on this subject based on the ideXlab platform.

  • Cardiac output and shunt during voluntary activity at different temperatures in the turtle, Trachemys scripta.
    Physiological and biochemical zoology : PBZ, 2003
    Co-Authors: Egle H. Krosniunas, James W. Hicks
    Abstract:

    Abstract Red‐eared slider turtles (Trachemys scripta) were chronically instrumented with blood flow probes for a long‐term study of voluntary behavior in an enriched laboratory setting. Cardiovascular measures consisting of total cardiac output ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\dot{Q}$ \end{document} tot), pulmonary blood flow ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp...

  • The Intracardiac Shunt as a Source of Myocardial Oxygen in a Turtle, Trachemys scripta.
    Integrative and comparative biology, 2002
    Co-Authors: Colleen G. Farmer, James W. Hicks
    Abstract:

    SYNOPSIS. The functional significance of many features of the reptilian cardiopulmonary system remains unknown; particularly the importance of cardiac shunts. One hypothesis for a physiological function for shunts is that they play a role in myocardial oxygenation and are therefore important when cardiac work is elevated. In this study we examined cardiac function by monitoring electrocardiograms in red-eared slider turtles (Trachemys scripta) with a reduced myocardial oxygen supply. Exposing the animals to a hypoxic gas mixture reduced oxygen levels in the pulmonary venous return. When cardiac work was elevated during hypoxia, the electrocardiogram changed in a manner consistent with myocardial hypoxia, suggesting enrichment of the luminal blood with oxygen by the intracardiac shunt facilitates cardiac performance.

  • Reductions in systemic oxygen delivery induce a hypometabolic state in the turtle Trachemys scripta.
    American journal of physiology. Regulatory integrative and comparative physiology, 2001
    Co-Authors: Björn Platzack, James W. Hicks
    Abstract:

    We investigated the effects of vagal reductions in O2 delivery on oxygen consumption (V˙o 2) in the anesthetized freshwater turtle Trachemys scripta. Specifically, these experiments tested the hypo...

Tobias Wang - One of the best experts on this subject based on the ideXlab platform.

  • adenosinergic regulation of the cardiovascular system in the red eared slider Trachemys scripta
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2014
    Co-Authors: William Joyce, Tobias Wang
    Abstract:

    Abstract Few studies have investigated adenosinergic regulation of the cardiovascular system in reptiles. The haemodynamic effect of a bolus intra-arterial adenosine injection (2.5 μM kg − 1 ) was investigated in nine anaesthetised red-eared sliders ( Trachemys scripta ). Adenosine caused a transient bradycardia, which was accompanied by systemic vasodilatation as evidenced by an increase in systemic flow and a decrease in systemic pressure. Meanwhile, pulmonary flow fell significantly. Both the bradycardia and increase in systemic conductance were significantly attenuated by theophylline (4 mg kg − 1 ), demonstrating an involvement of P 1 receptors. These results suggest that adenosine is likely to play a significant role in reptile cardiovascular physiology. In turtles specifically, adenosinergic regulation may be particularly relevant during periods of apnoea.

  • The cardiovascular responses of the freshwater turtle Trachemys scripta to warming and cooling.
    The Journal of experimental biology, 2004
    Co-Authors: Gina Galli, E W Taylor, Tobias Wang
    Abstract:

    Seven freshwater turtles Trachemys scripta were instrumented with flow probes and cannulated for blood pressure measurements. The turtles were warmed from 24 to 34 degrees C, and cooled down to 24 degrees C, with and without atropine. Animals exhibited a hysteresis of heart rate and blood flow to both the pulmonary and systemic circulations, which was not cholinergically mediated. Blood pressure remained constant during both warming and cooling, while systemic resistance decreased during heating and increased during cooling, indicating a barostatic response. There was a large right-to-left (R-L) shunt during warming and cooling in untreated animals, which remained relatively constant. Atropinisation resulted in a large L-R shunt, which decreased during warming and increased during cooling. Nevertheless, heating rates were the same in untreated and atropinised animals, and cooling rates were significantly longer in atropinised animals, indicating that shunt patterns contribute little to heat exchange.

Barbour, Roger W. - One of the best experts on this subject based on the ideXlab platform.

William Joyce - One of the best experts on this subject based on the ideXlab platform.

  • adenosinergic regulation of the cardiovascular system in the red eared slider Trachemys scripta
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2014
    Co-Authors: William Joyce, Tobias Wang
    Abstract:

    Abstract Few studies have investigated adenosinergic regulation of the cardiovascular system in reptiles. The haemodynamic effect of a bolus intra-arterial adenosine injection (2.5 μM kg − 1 ) was investigated in nine anaesthetised red-eared sliders ( Trachemys scripta ). Adenosine caused a transient bradycardia, which was accompanied by systemic vasodilatation as evidenced by an increase in systemic flow and a decrease in systemic pressure. Meanwhile, pulmonary flow fell significantly. Both the bradycardia and increase in systemic conductance were significantly attenuated by theophylline (4 mg kg − 1 ), demonstrating an involvement of P 1 receptors. These results suggest that adenosine is likely to play a significant role in reptile cardiovascular physiology. In turtles specifically, adenosinergic regulation may be particularly relevant during periods of apnoea.

John K. Tucker - One of the best experts on this subject based on the ideXlab platform.

  • Homing in the Red-Eared Slider (Trachemys scripta elegans) in Illinois
    Chelonian Conservation and Biology, 2008
    Co-Authors: John K. Tucker, James T. Lamer
    Abstract:

    ABSTRACT We recaptured 40 of 69 (58%) female red-eared sliders (Trachemys scripta elegans) that had been moved 3 km from Swan Lake to Long Lake in west-central Illinois. Twenty-one of 33 (63.6%) control turtles that were not moved from Swan Lake were recaptured. The similarity in recapture rates between control and experimental turtles suggests that statistically all translocated turtles returned to Swan Lake regardless of the actual percentage recaptured. We also found that males were less likely than females to make cross-river movements between backwaters of the Illinois River. The frequency of cross-river movements in sliders was small, only 86 recaptures (0.8%) out of a total of 10,373 recaptures made from 19,018 trapped turtles marked and released at our study areas between 1994 and 2006.

  • Claw Function of Hatchling and Adult Red-Eared Slider Turtles (Trachemys scripta elegans)
    Chelonian Conservation and Biology, 2006
    Co-Authors: Daniel A. Warner, John K. Tucker, Nirvana I. Filoramo, J. Brian Towey
    Abstract:

    ABSTRACT We examined variation in claw length of hatchling and adult red-eared slider turtles (Trachemys scripta elegans). Hind claw length of adult females was greater than that of adult males, and we suggest that increased hind claw length in females (a previously unrecognized sexually dimorphic trait) may serve as an adaptation for nest construction. In addition, front and hind claws of hatchlings newly emerged from their eggs were longer than the front and hind claws of hatchlings that were captured during their migration toward aquatic habitats; relatively long claws could aid hatchlings in their escape from nests and migration to aquatic habitats.

  • Short-term Water Potential Fluctuations and Eggs of the Red-eared Slider Turtle (Trachemys scripta elegans)
    Transactions of the Illinois State Academy of Science, 2001
    Co-Authors: John K. Tucker, Gary L. Paukstis, Fredric J. Janzen
    Abstract:

    We exposed eggs of the red-eared slider turtle ( Trachemys scripta elegans) to short duration (i.e., 48 hours) changes in water potential at two embryonic ages (20 and 40 days). Survivorship to hatching did not differ by substrate water potential or among treatments. Net change in egg mass, a measure of net water exchange between the egg and substrate, was affected by treatments. However, treatments had no effect on hatchling mass, carcass mass, yolk mass, or incubation period. Eggs and embryos are able to exploit beneficial short-term increases in water potential and withstand adverse ones.

  • Size-biased Mortality Due to Predation in a Nesting Freshwater Turtle, Trachemys scripta
    The American Midland Naturalist, 1999
    Co-Authors: John K. Tucker, Nirvana I. Filoramo, Fredric J. Janzen
    Abstract:

    Abstract Differential survivorship within or between stages is an important component of most explanations of turtle reproductive patterns. We tested the null hypothesis that a sample of adult female Trachemys scripta found killed by predators was a random sample of adult females found nesting at a site in W-central Illinois by comparing plastron lengths of the two samples. Mean plastron length of 19 dead female T. scripta was significantly smaller than mean plastron length of 79 females found alive. Apparently smaller females were at greater risk of mortality than were larger ones. Cubic spline analysis indicated that mortality was strongly concentrated among the smallest and perhaps youngest nesting females and was distinctly nonlinear. This finding was consistent with the suggestion that the minimum threshold of maturation size was influenced by the size at which the probability of predation decreases.

  • OVERWINTER SURVIVAL BY HATCHLING SLIDERS (Trachemys scripta) IN WEST-CENTRAL ILLINOIS
    Journal of Herpetology, 1998
    Co-Authors: John K. Tucker, Gary C. Packard
    Abstract:

    Turtles are perceived to be among the longest lived vertebrates (Gibbons, 1987), but relatively few individual turtles actually live long lives. This certainly is the case for slider turtles (Trachemys scripta) because survivorship of hatchlings and juveniles is extraordinarily low compared to that of adult animals (Frazer et al., 1990; Tucker and Moll, 1997). Much of the mortality falls on hatchlings, and much of this mortality occurs before animals have emerged from their nests (Frazer et al., 1990). Winter may be an especially critical period for hatchling sliders in populations near the northern limit of the distribution, because neonates generally remain inside their nests throughout the winter and consequently may be exposed to ice and cold (Packard et al., 1997). At our study site, located about 170 km south of the northern limit of the species range, hatchlings were never found emerging from nests in the fall despite annual searches for fall emerging hatchlings (Tucker, 1997, and unpublished). We tested predictions emerging from a laboratory study of freeze tolerance in neonatal sliders (Trachemys scripta). Hatchlings that contact ice in frozen soil are unable to supercool appreciably because the integument-affords little protection against inoculative freezing (Packard et al., 1997). Inoculative freezing occurs when ice crystals come into contact with the integument of hatchling sliders after they are cooled below their equilibrium freezing point but before they reach their supercooling limit (Packard et al., 1997). Frozen animals generally die within 36 h of inoculation. Thus, we predicted that turtles overwintering in the field generally would not tolerate prolonged exposure to ice and cold. Eggs were collected in 1995 from nests located near Stump Lake, Jersey County, Illinois (Tucker and Moll, 1997; Tucker, 1997). Eggs were placed on moist vermiculite, with each clutch assigned to a separate plastic box. These boxes contained a mixture of 1.11 g water 1.0 g vermiculite (water potential = -150 kPa). The eggs then were incubated to hatching at temperatures near 26 C.