GIBBS, V.K.*; WATTS, S.A.; Univ. of Alabama at Birmingham: Exposure temperature affects biochemical and cellular composition of the gonad in the sea urchin Lytechinus variegatus (Echinodermata: Echinoidea)

Temperature is one of the most important proximate factors affecting the biology of ectothermal organisms. In Lytechinus variegatus, water temperature affects the reproductive cycle in field populations, suggesting gonad composition may be dependent, in part, on temperature. In this study, adult L. variegatus were exposed to one of three temperatures indicative of average field temperatures of winter, spring/fall, or summer (16, 22, or 28&degC, respectively). Individuals were maintained in recirculating aquaria held at constant temperature and were fed a formulated diet ad libitum for 8 weeks. At the end of 8 weeks, absorption efficiencies of total dry matter and carbohydrate were highest for individuals held at 28&degC. Absorption efficiencies of protein and lipid were highest for individuals held at 16&degC. These data indicate that patterns of nutrient absorption are affected by temperature (a pattern also observed in some crustaceans). Gonad production was highest at 22&degC, primarily the result of high consumption rates. Proximate analysis of the gonad tissue revealed that protein content was highest for individuals held at 22&degC and lipid content was highest for individuals held at 16&degC. Carbohydrate content did not differ significantly with temperature. Histological analyses of cell populations within the gonad tissue suggest that temperature affects the allocation of absorbed nutrients to either storage cells or gametes. This study was supported by the Mississippi-Alabama Sea Grant Consortium. Diets were kindly provided by Dr. Addison Lawrence, Texas A&M.