On the nature of pre-freeze mortality in insects:: water balance, ion homeostasis and energy charge in the adults of Pyrrhocoris apterus

Three acclimation groups [i.e. non-diapause (LD), diapause (SD) and diapause, cold-acclimated (SDA)] of the adult bugs Pyrrhocoris apterus differed markedly in their levels of chill tolerance. Survival time at a sub-zero, but non-freezing, temperature of -5degreesC (Lt50) extended from 7.6 days, through 35.6 days, to >60 days in the LD, SD and SDA insects, respectively. The time necessary for recovery after chill-coma increased linearly with the increasing time of exposure to -5degreesC, and the steepness of the slope of linear regression decreased in the order LD>SD>SDA. The capacity to prevent/counteract leakage of Na+ down the electrochemical gradient (from haemolymph to tissues) during the exposure to -5degreesC increased in the order LD