Metabolic consequences of behavioural hypothermia and oxygen detection in submerged overwintering frogs

Metabolic consequences of behavioural hypothermia and oxygen detection in submerged overwintering frogs

Boutilier R G; Tattersall G J; Donohoe P H

Zoology-Analysis of Complex Systems

2000

2000

The common frog, Rana temporaria, overwinters under the ice of frozen lakes and ponds, during which time metabolic, respiratory and behavioural adjustments act in concert to conserve metabolic fuels by promoting aerobic metabolism. Animal behaviour under the ice is poorly understood, but given that spatial and temporal gradients for temperature and oxygen develop throughout the winter, behavioural thermoregulation may allow the selection of aerobic microenvironments that are conducive to overwintering survival. Accordingly, we have examined the thermoregulatory behaviour and metabolism of cold-submerged frogs in an experimental 'gradient chamber' designed to mimic overwintering conditions in nature. The preferred temperature of 7 degrees C in normoxia decreases to 1.5 degrees C in severe hypoxia, and coincides: with an aerobic metabolic saving of 70-85% and a delay in the onset of a runaway lactacidosis. Following intense exercise, temperature preferences are also lowered from 6.7 degrees C to 3.6 degrees C for upwards of 7 hours in a fashion reminiscent of the 'behavioural hypothermia' response to hypoxia. Cold-submerged frogs are also able to detect isothermal variations in dissolved oxygen and spend 70% of their time at oxygen partial pressures that promote aerobic metabolism. The ability to exploit gradients of oxygen and temperature has strong ecological relevance to over-wintering since the behavioural selection of preferred microhabitats is consistent with minimising the metabolic stresses associated with either hypoxia or hypothermia and promoting survival.

hypoxia; exercise; oxygen; recovery; Zoology; temperature; amphibians; rana-catesbeiana; bullfrogs; metabolic fuels; metabolic suppression; muscosa; temperature gradients

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Journal Article or Conference Abstract Publication

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