Abstract
The effects of temperature on compound action potential velocities in peripheral nerves from antarctic fishes and invertebrates were compared with those from temperate poikilotherms. Conduction velocity is a linear function of temperature, with sharp upper and lower limits corresponding to ‘heat-block’ and ‘cold-block’. Slope, x-intercept and cold- and heat-block temperatures were reduced in antarctic poikilotherms. Cold-block could not be demonstrated, but heat-block occurred around 31 °C. Neuromuscular activation failed between 16 ° and 22 °C in antarctic preparations. Fast fibres show steeperV/T slopes than slow fibres, but the two classes tend to converge on a common x-intercept; normalised velocities give nearly identical slopes, indicating that both large and small fibres are affected equally by temperature. Similarities in pattern between shortand long-term cold adaptation in both poikilotherms and endotherms suggest a common mechanism for membrane adaptations to low temperatures, and are consistent with the hypothesis of homeoviscous adaptation.
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