The effect of high lethal temperatures on the muscle of the crayfish, astacus pallipes lereboullet; a biochemical and electrophysiological

Abstract

The phenomenon of temperature adaptation, as measured by the mobility of the heat death point, was demonstrated in Aatacus pallipes Lereboullet. Analysis of muscle, haemolymph and environment during lethal high temperature exposure showed dramatic Na(^+) and K(^+) concentration changes in all three compartments. In all cases the monovalent cations showed a net movement down their respective electro-chemical gradients, although this was sometimes only observed after a brief initial period during which the ions tended to exhibit a net movement up their electro-chemical gradients. The results indicated that heat death occurred when the haemolymph K(^+) concentration rose to about 9 mM. No relationship between the haemolymph Na(^+) concentration and the heat death point was observed. Electrophysiological experiments indicated that lethal high temperatures caused an increase in the conductivity (-, permeability) of the sarcolemma following comparable exposure times to those causing heat death in the whole animal. The Mg(^++)activated ATPase (EC 3.6.1.3.) which is involved in the control of sarcolemmal permeability was shown to be inactivated by lethal high temperatures. It was therefore concluded that the increased sarcolemmal permeability was caused by the thermal inactivation of this enzyme. The spontaneous activity of the CNS was only slightly affected by exposure to lethal high temperatures. Raising the extracellular K* concentration to the levels observed in animals at the time of heat death caused a massive increase in nervous activity. The sarcolemmal Mg (^++) activated ATPase from warm adapted crayfish was shown to be more resistant to high temperatures than that from cold adapted crayfish. This could be correlated with the greater heat resistance of the sarcolemmal Mg(^++) activated ATPase and conductivity seen in the warm adapted animals. It is proposed that the primary lesion of heat death in Astacus pallipes Lereboullet is the thermal inactivation of the sarcolemmal Mg(^++) activated ATPase which allows muscle K(^+) to move into the haemolymph. The activity of the CNS is increased markedly by the high haemolymph K(^+) resulting in loss of coordination and death. The thermal sensitivity of the Mg(^++) activated ATPase is modified by the previous thermal history of the crayfish and is involved in the mechanism of temperature adaptation.