Responses to Rapid Temperature Change in Vertebrate Ectotherms

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Abstract
Vertebrate ectotherms often encounter rapid, large scale changes in body temperature. In this paper, I discuss the direct effects of changing body temperature on physiological parameters, as well as corrective responses initiated by the animal. For many biological functions, mean body temperature provides a useful measure of the thermal effects produced by an altered environmental temperature. Under most conditions, the fins and body surface of fish are more important avenues of heat exchange than the gills. The local thermal sensitivity of peripheral blood vessels results in vasomotor adjustments which can alter thermal conductivity. Acid-base balance is challenged by changes in body temperature. Shifts in body temperature also alter metabolic demands, enzyme conformation, ionic and osmotic relationships, spontaneous activity levels and nervous system function. Compensatory mechanisms include behavioral thermoregulation, by which animals seek to avoid stressful thermal environments, and autonomic restorative responses such as high temperature panting in reptiles. Water breathers may initiate anticipatory responses to minimize arterial oxygen fluctuations during termperature change. The organization of the central neuronal network underlying the above regulatory responses is unclear. Both air and water breathers are able to initiate compensatory acid-base responses, but the strategies utilized by the two groups are quite different. Altered body temperature initiates long-term acclimation responses, and if rapid, can also trigger stress responses.

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