WILLIAMS, J.B.; RUEHL, N.C.; LEE, R.E.; Miami Univeristy, Oxford Ohio; Miami Univeristy, Oxford Ohio; Miami Univeristy, Oxford Ohio: Do Cryoprotectants Enhance Dehydration Resistance in the Overwintering Larvae of the Gall Fly, Eurosta solidaginis?

Low molecular mass sugars and polyols, termed cryprotectants, enhance cold-hardiness and freeze tolerance in many overwintering insects. Recently, it was suggested that high concentrations of these compounds may have originally functioned to increase dehydration resistance rather than to promote cold tolerance. The cryoprotectant sorbitol is produced in the overwintering gall fly larvae when they experience temperatures below 10�C and is catabolized at higher temperatures (~20�C). We manipulated hemolymph osmolality (presumably by changing sorbitol levels), in mid-winter larvae by holding them at 20�C for 48 h before transfer to 10, 5, or 0�C. After 48 h exposure to 10, 5, or 0�C, larvae increased their hemolymph osmolality (820 mOsm●kg^-1) by ~13% compared to those held at 20�C. Larvae in the 10, 5, and 0�C experimental groups also had a significantly lower water loss rate (1.63 μg●mm^-2●h^-1) than larvae in the 20�C control group (1.97 μg●mm^-2●h^-1). Interestingly, the increase in hemolymph osmolality decreased the rate of water loss much more than would be predicted based on the colligative lowering of the water vapor potential of the insects� hemolymph. Supported by NSF#IBN-0090204