Turtle Chrysemys Picta Bellii Research Articles

Is the hypoxic ventilatory response driven by blood oxygen concentration?

![Figure][1] Bill Milsom and Tobias Wang discuss the impact of Mogens Glass, Robert Boutilier and Norbert Heisler's classic paper ‘Ventilatory control of arterial P O2 in the turtle Chrysemys picta bellii : Effects of temperature and hypoxia’, published in Journal of Comparative

Characterization of Western Painted Turtle Bycatch in Fyke Nets During Freshwater Fish Population Assessments

AbstractIn fisheries management, fish populations are assessed using various net types that invariably also capture nontarget species. Although the bycatch of turtles tends to be a common occurrence, data describing the bycatch of turtles during freshwater fish sampling are lacking. To improve the available knowledge base concerning the bycatch of turtles during fish sampling, we characterize the dynamics of western painted turtle Chrysemys picta bellii bycatch in unbaited modified fyke nets used in fish population sampling in northeastern South Dakota. We collected data from June to September during fish population assessments in 39 lakes and nine impoundments between 2007 and 2012. We characterize western painted turtle bycatch relating to water type (lake and impoundment) including catch rates (number of turtles/net night), size structure, and sex ratio. Catch rates were higher in impoundments than lakes. Total mean annual catch rates ranged from 1.07 to 3.28 for lakes and from 0.70 to 6.63 for impoundments and the variation among years was significant for both water types. We observed no annual variation in water surface area or mean depth, precluding either from explaining the variation in annual catch rates. We observed a significant relationship between mean depth and catch rate for lakes, but not impoundments. We observed no significant relationship relating surface area to catch rate for lakes or impoundments. Catch rates differed significantly from June to September for lakes but not impoundments. Annual variation in catch rates was best explained by the previous winter precipitation for both water types. The sex ratio was skewed toward males and differed significantly from June to September for lakes but not impoundments. The size structure was skewed toward large turtles. Understanding bycatch dynamics during fish population assessments is a critical first step to understanding the impact of biological sampling on nontarget species and may prove useful in minimizing future bycatch of western painted turtles.

Anoxia‐mediated elevation in phasic GABAA receptor currents is essential for anoxia‐tolerance in turtle cortex

In mammalian brain, anoxia induces hyper‐excitability and cell death; however, the western painted turtle Chrysemys picta bellii is anoxia tolerant, neuronal activity is depressed by anoxia and cell death does not occur. In anoxic turtle brain [γ‐aminobutyric acid] (GABA) is elevated suggesting that the mechanism(s) responsible for anoxia‐tolerance involve GABAergic synaptic transmission. The objective of this study was to investigate the neuroprotective role of endogenous phasic GABAA receptor currents during anoxia in turtle cortex. Using whole‐cell patch clamp techniques we identified phasic GABA‐mediated IPSC's that double in amplitude with anoxia (41.2 ± 1.6 to 82.1 ± 2.1 pA) resulting in a 60–70% decrease in spontaneous action potential frequency. Inhibition of phasic GABAA receptor currents with gabazine resulted in hyper‐excitability. We conclude that anoxia increases phasic GABAA receptor peak currents resulting in a “shunting current” that prevents further depolarization and hyper‐excitability. Research supported by OGSST grant to DH and NSERC grant to LB.

Bacterial infection and tissue-specific Hsp72, -73 and -90 expression in western painted turtles

Heat shock proteins (Hsps) are molecular chaperones that assist intracellular folding, assembly and translocation of proteins in prokaryotic and eukaryotic cells. A variety of stresses including hyperthermia, radiation, heavy metals, ischemia, anoxia and reoxygenation have been shown to increase the expression of Hsps. Likewise, bacterial infection represents a stress for the host cell. In this study, expression of the constitutive (Hsp73) and inducible (Hsp72) isoforms of Hsp70 and Hsp90 was monitored in brain, heart, liver and skeletal muscle from the western painted turtle Chrysemys picta bellii diagnosed with Septicemic Cutaneous Ulcerative Dermatitis (SCUD). This disease is caused by a gram-negative bacterium probably belonging to the Citrobacter spp. The expression of Hsp73 increased 1.8-fold in brain and liver, 2.2-fold in heart but did not change in skeletal muscle; Hsp72 expression increased 5.5-fold in brain and 3-fold in liver but did not change in heart or skeletal muscle; Hsp90 expression increased 9-fold in brain, 2.7-fold in heart and 2.4-fold in skeletal muscle but did not change in liver. These results suggest a tissue-specific Hsp response during bacterial infection and a role for Hsps in immunopathological events in reptiles.

Lactate accumulation in the shell of the turtle Chrysemys picta bellii during anoxia at 3°C and 10°C

Lactate concentrations were measured in the shell and plasma of the turtle Chrysemys picta bellii after 3 months of submergence anoxia at 3°C and during and after 9 days of submergence anoxia at 10°C. Liver and skeletal muscle lactate levels were also measured in control and anoxic animals at each temperature. At 3°C, mean shell lactate concentration (N=4) reached 133mmolkg-1shellmass and plasma lactate levels were 144mmoll-1; at 10°C, shell and plasma lactate concentrations (N=5) rose in parallel during anoxic exposure, to 70.8mmolkg-1shellmass and 78.9mmoll-1, respectively, and returned in parallel to control levels during 9 days of recovery. At the end of the anoxic periods, an estimated 44% of the total body lactate resided in the shell at 3°C and 43% at 10°C, and indirect evidence suggests that the shell buffered these same fractions of the acid load. Because of the high lactate concentration per kilogram of shell water (416mmolkg-1 at 3°C; 221mmolkg-1 at 10°C) and the known formation of calcium lactate complexes, it is postulated that most of the lactate existed in the shell in combined form. I conclude that sequestration of lactate within the shell represents a potentially major adaptation to anoxic acidosis for this animal and, together with the previously described release of shell carbonates, may account for up to two-thirds of the total lactic acid buffering in this animal.

Hatchling Size in the Turtle Chrysemys picta bellii from Western Nebraska: Relationships to Egg and Maternal Body Size

Eggs of the turtle Chrysemys picta bellii from four western Nebraska populations were incubated under laboratory conditions to compare egg size and hatchling size as measures of offspring size among populations and in the context of maternal body size. Generally, hatchling size (mass and carapace length) was linearly related to egg size (mass, width, and length) and did not vary between the two years of the study or among populations after adjusting for egg size. However, hatchling carapace length adjusted for egg width was greatest in a population with the most elongate eggs indicating that linear egg measurements may not be useful for interpopulation comparisons. The smaller range of variation, but greater variability in hatchling size relative to egg size and a narrow range of maternal body sizes (carapace length and mass), seemed to preclude a correlation between maternal body size and hatchling size within two populations. In two other populations, hatchling carapace length, egg width, and egg length increased with maternal carapace length by a common slope, although egg wet mass had a steeper slope than did hatchling wet mass. It is probable that under natural incubation conditions (e.g., warmer, drier, and more variable), hatchling mass may increase only slightly or not at all with maternal body size. My results suggest that both hatchling and egg size should be considered in turtle life history studies, particularly for models that predict delayed sexual maturation when offspring size and survival increase with maternal body size and age.

Microcalorimetric measurement of reversible metabolic suppression induced by anoxia in isolated hepatocytes.

The metabolic suppression due to anoxia in hepatocytes from the anoxia-tolerant turtle Chrysemys picta bellii was measured directly using microcalorimetric techniques. The normoxic heat flux from hepatocytes in suspension (25 degrees C) was 1.08 +/- 0.08 mW/g cells and decreased by 76% to 0.26 +/- 0.03 mW/g cells in response to anoxic incubation. After an acute decrease in temperature (to 10 degrees C) anoxic heat flux dropped by 96% relative to the normoxic control at 25 degrees C. The relative decrease in heat flux at both temperatures was similar, 76% at 25 degrees C and 68% at 10 degrees C. From the caloric equivalent of glycogen fermentation to lactate the heat flux from lactate production was calculated to be -93 microW/g cells (25 degrees C), and this accounted for 36% of the anoxic heat flux. When the enthalpy change associated with the release of free glucose (from glycogen breakdown) is considered, an additional 6% of the anoxic heat flux can be accounted for. Therefore, a portion of the anoxic heat flux is unaccounted for (58%), resulting in an "exothermic gap." This differs from the normoxically incubated hepatocytes where the indirect calorimetric measurement of heat flux (hepatocyte O2 consumption) could fully account for the calorimetrically measured heat flux. When normoxic hepatocytes were inhibited with cyanide, a rapid suppression in heat flux was observed. Because rapid reequilibration to a lower, cyanide-induced steady state occurred in < 15 min, it is also assumed that there is no short-term Pasteur effect in this tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxidative cost of breathing in the turtle Chrysemys picta bellii

We estimated the cost of breathing of turtles by measuring ventilation and oxygen consumption during air breathing and CO2 breathing. We assumed that any increment in oxygen consumption due to hypercapnic hyperpnea was due to the metabolic cost of the increased breathing. Six turtles were studied while breathing air and then 5% CO2 in air after at least 12 h breathing each gas. For the measurements, the turtles were submerged unrestrained in water at 20 degrees C and were free to raise their heads into a ventilated chamber. Tidal volumes were measured by the pressure changes in the chamber, and oxygen consumption was measured by conventional open-circuit respirometry. Ventilation increased markedly during CO2 breathing up to 50 times the control level, but oxygen consumption increased only slightly. Assuming no depression in nonventilatory metabolism, our data indicate an oxidative cost of breathing on the order of 1% of the total metabolic rate at rest. This is far less than the 15-20% cost predicted from published work (Kinney et al., Respir. Physiol. 31: 327-332, 1976) on a closely related species of turtle and is consistent with earlier work in our laboratory. We conclude that the cost of breathing in turtles is low, similar to other air-breathing vertebrates, and therefore the existing notion that turtle breathing is expensive and inefficient should be discarded.

Force and acid-base state of turtle cardiac tissue exposed to combined anoxia and acidosis

We measured contractile force of ventricular strips form the turtle Chrysemys picta bellii exposed to 1 h of combined anoxia and acidosis (pH 7.0) at 20 degrees C. Strips either beat spontaneously (self-paced) or in response to electrical stimulation (paced at 12, 24, or 36 beats/min). Tissue [lactate] and intracellular pH (pHi) were measured in control strips and at the end of anoxia-acidosis. In self-paced strips, at normal extracellular Ca2+ concentration ([Ca2+]o) (1 mM), both rate and force fell significantly after 1 h of anoxia-acidosis to 54 and 17.1%, respectively, of control values. Increased [Ca2+]o to 10 mM at 30 min had a small but significant positive effect on both rate and force. Contractile force of paced strips also fell progressively during anoxia-acidosis, but the decrease varied directly with pacing frequency. Under all cases of anoxia-acidosis, pHi fell significantly from the control value of 7.53; in paced strips, acidosis was most severe at 36 beats/min (pHi 6.75), and in self-paced strips, pHi (approximately 6.85) was independent of [Ca2+]o. Based on this and previous work, we conclude that combined anoxia-acidosis, similar to that observed in vivo after prolonged anoxic submergence, profoundly depresses cardiac function. Both hypercalcemia and bradycardia improve performance in this extreme state, but these effects are not as great as when anoxia and acidosis occur alone.

Temperature Effects on the Responses to Prolonged Submergence in the Turtle Chrysemys picta bellii. II. Metabolic Rate, Blood Acid-Base and Ionic Changes, and Cardiovascular Function in Aerated and Anoxic Water

Pulmonary and nonpulmonary O2 uptake (\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{wasysym} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document}${\mathrm{\dot{V}_{O_{2}}}}$\end{document}) were measured on freshwater turtles (Chrysemys picta bellii) at 3, 10, 15, and 20 C, and these data were related to the physiological responses of turtles to submergence in aerated vs. anoxic water. Total \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{wasysym} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document}${\mathrm{\dot{V}_{O_{2}}}}$\end{document} increased with temperature...

Temperature Effects on the Responses to Prolonged Submergence in the Turtle Chrysemys picta bellii. I. Blood Acid-Base and Ionic Changes during and following Anoxic Submergence

Blood acid-base status and plasma ion concentrations and osmolality of freshwater turtles (Chrysemys picta bellii) were measured periodically during and following submergence in N₂-equilibrated water (Po₂ < 5 torr) at 3, 10, 15, and 20 C. Submergence durations that resulted in similar reductions in blood pH or in plasma [HCO₃⁻] at each temperature were 12 h at 20 C, 3 days at 15 C, 10 days at 10 C, and 13 wk at 3 C. At 3 C, 75% of the fall in pH during anoxia was due to metabolic acidosis, but the contribution of respiratory acidosis to the pH drop increased with temperature, being 50% at 10 C, 73% at 15 C, and 73% at 20 C. Plasma strong-ion difference decreased much less during anoxia than had been predicted on the basis of the increase in plasma lactate, owing to compensatory changes in plasma ions, including increased [K⁺], total [Ca⁺⁺], and total [Mg⁺⁺] and decreased [Cl⁻]. The magnitude of these ion changes was directly correlated with the increase in plasma lactate, which in turn was inversely correlated with temperature. Plasma lactate concentrations ranged from 96 mM at 3 C to 19.7 mM at 20 C. Recovery from anoxic acidosis at all temperatures occurred in two stages, a respiratory stage that rapidly restored blood pH and lowered blood PCo2 below control values and a slower ionic stage that corrected plasma lactate and the associated disturbances in other plasma ions. Plasma osmolality increased during anoxia, and the extent of the increase varied inversely with temperature, as did the net increase in measured plasma ions. We conclude that the prolonged tolerance to anoxia at 3 C is not due to specialized mechanisms absent at higher temperatures; rather, slow accumulation of plasma lactate, modest hypercapnia, and effective compensatory ion changes markedly retard the development of acidosis at this temperature.

Ventilatory control of arterial PO 2 in the turtleChrysemys picta bellii: Effects of temperature and hypoxia

Ventilation, pulmonary O2 uptake, arterial blood gases and pH were measured in fresh water turtles,Chrysemys picta bellii, during voluntary diving and surfacing at temperatures of 10, 20 or 30°C. At each temperature, the animals were also exposed to declining levels of inspired O2 concentration with blood samples taken at various stages of breath holding and during episodes of breathing.

Long-term submergence at 3 degrees C of the turtle Chrysemys picta bellii in normoxic and severely hypoxic water. III. Effects of changes in ambient and subsequent air breathing

Western Painted Turtles, Chrysemys picta bellii (N = 5), were maintained submerged and apneic for 90 days: days 0-21 in severely hypoxic water (PO2 = 0-5 mmHg), days 22-43 in aerated water (PO2 approximately 160 mmHg), and days 44-90 again in hypoxic water. From day 90 onward, the water was aerated and the turtles were allowed access to the air; water and air temperatures were maintained at 3 degrees C. Arterial blood samples were taken periodically and analysed for PO2, PCO2, pH, [Na+], [K+] [Cl-], [lactate-], [glucose] and haematocrit. Plasma [HCO3-] was calculated for all samples and total plasma calcium was measured on samples from two animals. Each exposure to low PO2 water caused progressive lactic acidosis and a transient respiratory acidosis with an accompanying fall in plasma [Cl-] and rise in plasma [K+] and [calcium]. During the intervening period in aerated water, blood pH recovered significantly (from 7.33 to 7.74 in 7 days), due primarily to a fall in PCO2 (from 23.5 to 10.6 mmHg), while [lactate-] remained unchanged (at about 50 mM), and [HCO-3] rose slightly. Plasma [K+] promptly returned to nearly normal values. When permitted to breathe on day 90, the three surviving turtles rapidly restored pH to normal by pronounced hyperventilation (PCO2 less than 5 mmHg). Metabolic acidosis, however, disappeared slowly with a t1/2 for [lactate-] and [HCO-3] restoration of about 2 weeks. We conclude that a wintering turtle can stabilize or even slightly improve its acid-base and ionic status by moving from an anoxic environment to well-oxygenated water. Further improvements can be gained by breathing air, but recovery proceeds at a very slow rate if the animal remains at 3 degrees C.

The Viability of Chrysemys picta Submerged at Various Temperatures

The Viability of Chrysemys picta Submerged at Various Temperatures