MARTIN, G.G.; WILKINSON, H.; Occidental College, Los Angeles; Occidental College, Los Angeles: Morphology and Function of the Hemocytes in Aplysia californica

We are interested in how environmental factors affect the physiology and immune responses of marine invertebrates. Presently we are trying to characterize the effects of temperature on the number and function of circulating hemocytes in A. californica. Using morphological techniques (LM, TEM, SEM) and differential centrifugation on metrizoic acid gradients, there seems to be a single type of circulating hemocyte. A typical hemocyte is ~6 �m in diameter with a central nucleus and numerous filopodia. The cytoplasm contains glycogen and a few granules containing acid phosphatase. Hemocytes rapidly spread on substrates and readily phagocytose bacteria. To assess whether temperature affects the number of circulating hemocytes, individual A. californica were equilibrated in temperature-controlled aquaria (15�C) for one week and then moved to aquaria at either 10, 15 or 20�C for another week. Hemolymph was sampled and analyzed for total hemocyte count (THC) and blood glucose levels (Sigma kit) at 1 hour, 24 hours and 1 week after immersion. Animals maintained at 10�C and 15�C for 1 week demonstrated a relatively stable THC, while animals transferred to 20�C exhibited a sharp rise in THC after 24 hours, and a return to �normal� levels by 1 week. Blood glucose levels of 15�C animals declined over the week whereas slugs at 10�C showed a peak at 24 hours and slugs at 20�C had variable glucose levels. Field studies on A. californica are in progress to determine if THCs are dependant upon body temperature in intertidal areas. Further lab studies will determine if rates of cell spreading and bacterial phagocytosis are also affected by temperature.