Thermal Acclimation in Several Species of Stored-Grain Beetles.

Abstract

The chill-coma temperatures, oxygen consumption at several constant temperatures, and fresh weights of adults of Cryptolestes ferrugineus (Steph.), Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.) and Tribolium castaneum (Hbst.) were determined before and after acclimation for 14 days at 15 deg C in the laboratory in Australia. Acclimation lowered the mean chill-coma temperatures of all species, but most in O. surinamensis. The oxygen consumption of insects that were free to move and of insects restrained during respirometry was reduced by acclimation. The curves relating respiration rate and temperature were shifted downwards by cold acclimation, but its effect on their slopes (i.e. on temperature sensitivity) varied between and within species. Similarly, the relative proportions of the change in the consumption rates of free insects acclimated at 15 deg C that were attributable to locomotor activity or to resting metabolism varied considerably. The weights of C. ferrugineus and R. dominica were increased by cold acclimation, but those of the other 2 species were not.