Meeting Abstract

P1.141  Sunday, Jan. 4  Dehydration Tolerance in the Rusty Crayfish (Orconectes rusticus) FINKLER, M.S.*; MYGRANT, M.S.; JACKSON, A.L.; Indiana Univ., Kokomo mfinkler@iuk.edu

Orconectes rusticus is a species of crayfish frequently found in rocky-bedded streams and rivers. Although adapted to an aquatic environment, O. rusticus does occasionally make terrestrial excursions, and may need to do so in situations such as when waterways dry and where rocky beds inhibit effective burrowing. During these terrestrial movements, O. rusticus may be at considerable risk of dehydration. In this study, we examined the desiccation tolerance of O. rusticus of various sizes to determine the ability of these crayfish to cope with dehydration. Loss of righting response (LRR) occurred when crayfish had lost 9.16 +/- 0.36% of their total body mass and 11.89 +/- 0.47% of their estimated body water contents. Hemolymph osmolality increased linearly with mass loss during desiccation, from ca. 470 mOsm to 800 mOsm at mean LRR. Larger crayfish had overall higher rates of evaporative water loss than did small crayfish, but had longer estimated survival times under dehydrating conditions. Our findings suggest that O. rusticus, like most crustaceans, is relatively intolerant of dehydration, and rely primarily on avoidance of desiccating conditions as protection from dehydration. Most terrestrial activity likely occurs during periods of relatively low temperatures and high humidities, when risk of dehydration is minimized. Moreover, it appears that only larger individuals may be capable of prolonged overland forays.