An investigation into the factors involved in acclimatization to temperature and death at high temperature in calliphora erythrocephala (meig)

Abstract

The heat resistance of Calliphora erythrocephala varies during the life history. The egg is most sensitive to high temperature and the puparium most resistant. Puparial resistance develops in the larval stage and declines in the young adult. This adult decline is temperature dependent and seems to be related to changes taking place during maturation. Evidence for the existence of development acclimatization was found to be contradictory, however, physiological acclimatization did occur in the adult. This latter form of acclimatization differs from the typical pattern observed with other species, for the increase in heat resistance with increasing temperature of acclimatization is not proportionate and it declines with adult age. The interaction of these factors makes resistance adaptation in Calliphora erythrocephala a complex phenomena. It is concluded that the primary lesion of heat death in adults is the uncoupling of the sarcosomal enzymes associated with oxidative phosphorylation of ɤ glycerophosphate. The heat sensitivity of this enzyme pathway is correlated with the heat death point of the whole animal and death is probably the result of a breakdown in ATF synthesis, which leads to the interruption of other energy dependent processes. The biochemical lesions during heat death are correlated with dramatic changes in the ultrastructure of sarcosomal cristae, which house the respiratory assemblies. This suggests that the structural and functional integrity of membrane-enzyme complexes are important factors in cellular metabolism. Studies on isolated sarcosomes have shown that the coupling of oxidative phosphorylation is influenced by both age and acclimatized state of the fly. The coupling enzymes are implicated in both the age dependent changes in heat resistance and also capacity adaptation. They are likely to be key factors in the temperature physiology of adult Calliphora.