Doctoral Dissertations

Date of Award

12-1987

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Zoology

Major Professor

A.C. Echternacht

Committee Members

Gerald Vaughan, Robert Gatten, Neil Greenberg, Roland Bagby, Dewey Bunting, Gordon Burghardt

Abstract

This study was conducted to determine whether certain methods and variables may influence results obtained in tests of the thermal tolerance of reptiles. Knowledge thus gained then allowed an examination of the geographic variation in the thermal tolerance of adult male Anolis carolinensis.

Comparisons of body to ambient temperature were made using animals equipped with thermocouples (a commonly employed method) and animals whose temperature was recorded by insertion of a rapid-reading cloacal thermometer. Individuals with thermocouples averaged 0.5 C below and the individuals without thermocouples 0.4 C above ambient temperature. The cause of lowered temperature in subjects equipped with thermocouples was posited to be due to enhanced evaporative heat loss.

A test was conducted to determine whether acute handling and social stress lead to increased metabolic rate which, in turn, could lead to an unhealthy condition in subordinates of collectively housed lizards, lowering their thermal tolerance. Oxygen consumption and lactate accumulation were measured in individuals subjected to these forms of stress. Both were found to significantly increase rates of aerobic and anaerobic respiration. Collective housing of Anolis, and possibly other reptiles, before thermal testing may increase experimental error.

High temperature tolerance was compared in castrated individuals treated with either testosterone filled or empty silastic tubes, acclimated to 20±2 C for 10 days. While the lizards were heated, the following responses were noted and body temperatures recorded at the onset of each: Escape movements, panting and onset of muscular spasms. No treatment effect was found for the response temperatures observed. Testosterone does not affect heat tolerance after low temperature acclimation in this species.

Three populations, along a latitudinal gradient, were tested for cold tolerance. After field determinations of the critical thermal minimum (cooling the subject until the loss of the righting response) yielded the appropriate acclimation temperature, the animals were acclimated to 9 C for 48 hours. Laboratory determination of critical thermal minimum revealed that the Tennessee population was significantly more cold tolerant than either Georgia or Florida populations (the latter two were not found to differ): this species consists of physiological races with regard to cold temperature tolerance.

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