EFFECTS OF TEMPERATURE ON REPRODUCTIVE NEUROENDOCRINE FUNCTION IN APLYSIA-CALIFORNICA

Egg laying in the gastropod mollusk Aplysia californica is a temperatu re-dependent behavior, facilitated by warm temperature and attenuated by cold. The purpose of this work was to determine which components of the reproductive axis controlling egg laying are affected by temperat ure. There were three neural/reproductive tissues investigated: (1) th e head ganglia that transmit neural signals to the neuroendocrine bag cells, (2) the bag cells that synthesize and secrete egg-laying hormon e (ELH), and (3) the ovotestis that extrudes eggs into the hermaphrodi tic duct in response to ELH. There was no significant effect of temper ature on the ability of ELH to stimulate egg laying, suggesting that t emperature does not alter responsiveness of the ovotestis to hormonal stimulation. There was evidence that the bag cells play a secondary ro le in mediating the effects of temperature on egg-laying behavior, tha t is, using both bioassays and radioimmunoassay for detection or measu rement of ELH, hormone secretion was shown to be inhibited by cooler t emperatures in some preparations. However, the inconsistency of this r esponse suggested that the primary effect of temperature is upstream f rom the bag cells. Results from an experiment in which the head gangli a were chemically stimulated to activate bag cell electrical activity suggested that the primary site of temperature regulation lies within the head ganglia. (C) 1996 Academic Press, Inc.