P1.198 Wednesday, Jan. 4 Effect of dehydration and freezing on cryoprotectant and ion distribution and hemolymph volume in the goldenrod gall fly, Eurosta solidaginis WILLIAMS, J.B.*; LEE, R.E.; Southern Illinois University; Miami University email@example.com
Extracellular freezing and dehydration concentrate hemolymph solutes, which can lead to cellular injury due to excessive water loss. To determine whether freeze tolerant larvae employ protective mechanisms against excessive cellular water loss we examined the effect of extracellular freezing and dehydration on hemolymph volume, and cryoprotectant and ion levels in the hemolymph. Dehydrated larvae or ones that had been frozen at -5 or -20°C had a significantly smaller proportion of their body water as hemolymph (26.0 to 27.4%) compared to controls (30.5%). Even with this reduction in water content, hemolymph osmolality was similar or only slightly higher in frozen or dehydrated individuals than controls (908 mOsm•kg-1), indicating these stresses led to a reduction in hemolymph solutes. Hemolymph and intracellular content of ions remained largely unchanged between treatment groups; although levels of Mg++ in the hemolymph were lower in larvae subjected to freezing (0.21±0.01 µg•mg-1dry mass) compared to controls (0.29±0.01 µg•mg-1dry mass), while intracellular levels of K+ were lower in groups exposed to low temperature (8.31±0.21 µg•mg-1dry mass). Whole body glycerol and sorbitol content was similar among all treatment groups, averaging 432±25 mOsm•kg-1 and 549±78 mOsm•kg-1 respectively. However, larvae subjected to dehydration and freezing at -20°C had a much lower relative amount of cryoprotectants in their hemolymph (~35%) compared to controls (54%) suggesting these solutes moved into intracellular compartments during these stresses. The correlation between reduced hemolymph volume (i.e. increased cellular water content) and intracellular movement of cryoprotectants may represent a link between tolerance of dehydration and cold in this species.