Meeting Abstract

74.1  Friday, Jan. 6  After the cold: the reestablishment of osmotic balance and neuromuscular function during chill-coma recovery in a cricket (Gryllus pennsylvanicus) MACMIILLAN, Heath A.*; WILLIAMS, Caroline M.; STAPLES, James F.; SINCLAIR, Brent J.; University of Western Ontario; University of Western Ontario; University of Western Ontario; University of Western Ontario hmacmil2@uwo.ca

When exposed to low temperatures most insects enter a state of chill-coma, where impaired nerve and muscle signal transmission renders movement impossible. This loss of neuromuscular function and the chilling-induced injuries that follow are associated with flux of ions and water from the hemolymph to the gut lumen during low temperature exposure. Although it is used regularly as a means of quantifying cold-tolerance in insects, little is known about the processes underlying chill-coma recovery. Using the fall field cricket (Gryllus pennsylvanicus), we characterized the return to osmotic homeostasis following prolonged (24 hour) chill-coma using atomic absorption spectrometry to quantify Na⁺, K⁺, Mg²⁺ and Ca²⁺ content of muscle, hemolymph and the three gut segments. Crickets recovering from chill-coma rapidly established ion concentrations in the hemolymph sufficient to re-polarize muscle membranes and permit coordinated leg movement, although hemolymph volume and total ion content did not return to normal for a further 2 hours. Using open-flow respirometry, we confirmed that an overshoot in the rate of resting CO₂ release (a measure of metabolic rate) during chill-coma recovery corresponds with the mobilization of ions and water back out of the gut in order to regain initial hemolymph volume. Thus, chill-coma recovery appears to require a reversal of the physiological effects of cold exposure in insects, but re-establishment of homeostasis may take far longer than expected from studying the recovery of movement.