Electronic Thesis and Dissertation Repository


Master of Science




Dr. Brent J. Sinclair


Low temperature performance affects the geographical distribution of insects. The lower critical temperature limits of chill-susceptible insects are likely determined by failure of ion and water balance at low temperature. I used phenotypic plasticity in the cold tolerance of Gryllus pennsylvanicus, and the naturally higher cold tolerance of Gryllus veletis to test the hypothesis that variation in low temperature performance is accompanied by variation in ion and water homeostasis at low temperatures. Low temperature acclimation and cold adaptation enhanced performance at low temperatures. Groups with higher cold tolerance had an enhanced ability to prevent or mitigate the migration of hemolymph Na+ and water into the digestive system, which ultimately resulted in smaller decreases in K+ equilibrium potentials at the muscle tissue. The ability to maintain ion and water balance as a result of changes in gut membrane permeability increased performance at low temperatures, and reduced the onset of chilling injury.