EBANKS, S.C.*; BRIX, K.V.; GROSELL, M.; University of Miami, RSMAS; University of Miami, RSMAS; University of Miami, RSMAS: Extra-cellular Volume and Solute Recovery in the Pond Snail Lymnaea stagnalis After Simulated Predatory Attack

To fully retract into its shell and reduce the risk of predation, the pond snail Lymnaea stagnalis releases as much as 40-60% of its hemolymph to the external environment. In doing so, it loses extra-cellular fluid and solutes including major osmolytes and micronutrients. Our objective was to determine the time necessary for adult snails to recover solutes and extra-cellular volume following a simulated predatory attack. At the initial time point, individual snail wet weight was determined and snails were stimulated to full retraction to simulate a predatory attack. Pallial fluid, which is composed of mainly hemolymph and limited volumes of urea, was collected and final wet weight was recorded. This procedure was repeated on sub-groups of the initial snails at selected intervals after the first sampling. Within 8 h following the initial sampling, L. stagnalis appears to recover hemolymph volume with no change in pH. Bicarbonate concentration recovered from reduced levels to the initial value (21.3 mM) in 4-6 h while the 13.4% decrease in resting osmotic pressure was recovered in 18-20 h. In contrast, copper (Cu) concentration did not recover within 24 h. Currently, sodium (Na⁺), chloride (Cl^–), and calcium (Ca²⁺) uptake measurements are being completed during the solute recovery phase. In preliminary experiments, L. stagnalis increased both Na⁺ and Ca²⁺ uptake from the water, while reducing Na⁺ efflux for the first 6 hours after simulated attack. Thus these snails are apparently capable of recovering main solutes readily through regulated uptake from the water while certain essential elements such as Cu may require an extended period of recovery. This work was supported by a grant from the NOAA Educational Partnership Program.