Hypoxia: Effects on Heart Rate and Respiration in the Snapping Turtle

Boyer, Don R.

doi:10.1126/science.140.3568.813

Cited by 28 publications

(6 citation statements)

References 7 publications

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“…http://mc.manuscriptcentral.com/icbiol Aerobic capacity is maintained under conditions of mild hypoxia, but is limited under extreme hypoxia Boyer 1963Boyer 1966Withers and Hillman 1983Pörtner et al 1991Branco et al 1993Wang et al 1994 Oxygen treatments in lab PBT PBT is unaffected by mild hypoxia, but is reduced under extreme hypoxia Hicks and Wood 1985Branco et al 1993Cadena and Tattersall 2009 http://mc.manuscriptcentral.com/icbiol Downloaded from https://academic.oup.com/icb/advance-article-abstract/doi/10.1093/icb/icy005/4985721 by guest on 26 April 2018…”

Section: Figure Legendsmentioning

confidence: 99%

High Temperature, Oxygen, and Performance: Insights from Reptiles and Amphibians

Gangloff

Telemeco

2018

Integrative and Comparative Biology

106

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Much recent theoretical and empirical work has sought to describe the physiological mechanisms underlying thermal tolerance in animals. Leading hypotheses can be broadly divided into two categories that primarily differ in organizational scale: 1) high temperature directly reduces the function of subcellular machinery, such as enzymes and cell membranes, or 2) high temperature disrupts system-level interactions, such as mismatches in the supply and demand of oxygen, prior to having any direct negative effect on the subcellular machinery. Nonetheless, a general framework describing the contexts under which either subcellular component or organ system failure limits organisms at high temperatures remains elusive. With this commentary, we leverage decades of research on the physiology of ectothermic tetrapods (amphibians and non-avian reptiles) to address these hypotheses. Available data suggest both mechanisms are important. Thus, we expand previous work and propose the Hierarchical Mechanisms of Thermal Limitation (HMTL) hypothesis, which explains how subcellular and organ system failures interact to limit performance and set tolerance limits at high temperatures. We further integrate this framework with the thermal performance curve paradigm commonly used to predict the effects of thermal environments on performance and fitness. The HMTL framework appears to successfully explain diverse observations in reptiles and amphibians and makes numerous predictions that remain untested. We hope that this framework spurs further research in diverse taxa and facilitates mechanistic forecasts of biological responses to climate change.

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Section: Figure Legendsmentioning

confidence: 99%

High Temperature, Oxygen, and Performance: Insights from Reptiles and Amphibians

Gangloff

Telemeco

2018

Integrative and Comparative Biology

106

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“…Lowe and Vance (1955) found the resistance time to the critical thermal maximum in Urosaurus ornatus varied inversely with the body size of the lizard. Size may affect body temperatures in a physiological fashion as well as by simple physical effect, since heart rates and other physiological processes in turtles that may affect thermal gradients have size correlates (Hutton et al 1960;Boyer 1963).…”

Section: Sizementioning

confidence: 99%

Ecology of the Basking Habit in Turtles

Boyer¹

1965

Ecology

Self Cite

173

105

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A combined field and laboratory study was conducted to assess the biological implications of the basking habit in turtles. The effect of light intensity and incidence angle, water and air temperatures, wind, and cloud cover upon rates of heat gain in turtles were investigated, and all were found to have importance. Biological factors of importance are behavior, shape, weight, and rarely, color; sex and species were not important except as they affect the other factors. A series of motivation studies was conducted to identify the environmental factors initiating and directing basking. The taxonomic incidence of the basking habit in turtles is discussed. Basking serves primarily as a method of thermal control, with secondary benefits in drying of the skin and shell.

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“…Adult turtles breathe mostly episodically under normoxic conditions, with respiratory events containing clusters of 4–6 breaths separated by apneas of various lengths (Funk and Milsom 1987; Johnson et al, 2008). During hypoxia, semi-aquatic turtles increase breathing frequency by decreasing the length of respiratory apneas (Boyer, 1963; Glass et al, 1983; West et al, 1989), and decreasing the number of breaths that occur within each respiratory event (Frische et al, 2000). Red-eared slider turtles produce a distinctive highly regular, singlet-breath pattern during hypoxia (Frische et al, 2000; Johnson et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Isolated adult turtle brainstems exhibit central hypoxic chemosensitivity

Bartman

Johnson

2018

Comparative Biochemistry and Physiology Part A: Molecular &

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During hypoxia, red-eared slider turtles increase ventilation and decrease episodic breathing, but whether these responses are due to central mechanisms is not known. To test this question, isolated adult turtle brainstems were exposed to 240 min of hypoxic solution (bath PO = 32.6 ± 1.2 mmHg) and spontaneous respiratory-related motor bursts (respiratory event) were recorded on hypoglossal nerve roots. During hypoxia, burst frequency increased during the first 15 min, and then decreased during the remaining 35-240 min of hypoxia. Burst amplitude was maintained for 120 min, but then decreased during the last 120 min. The number of bursts/respiratory event decreased within 30 min and remained decreased. Pretreatment with either prazosin (α-adrenergic antagonist) or MDL7222 (5-HT antagonist) blocked the hypoxia-induced short-term increase and the longer duration decrease in burst frequency. MDL7222, but not prazosin, blocked the hypoxia-induced decrease in bursts/respiratory event. Thus, during bath hypoxia, isolated turtle brainstems continued to produce respiratory motor output, but the frequency and pattern were altered in a manner that required endogenous α-adrenergic and serotonin 5-HT receptor activation. This is the first example of isolated reptile brainstems exhibiting central hypoxic chemosensitivity similar to other vertebrate species.

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Hypoxia: Effects on Heart Rate and Respiration in the Snapping Turtle

Cited by 28 publications

References 7 publications

High Temperature, Oxygen, and Performance: Insights from Reptiles and Amphibians

High Temperature, Oxygen, and Performance: Insights from Reptiles and Amphibians

Ecology of the Basking Habit in Turtles

Isolated adult turtle brainstems exhibit central hypoxic chemosensitivity

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