EFFECTS OF FOOD DEPRIVATION ON ENZYMATIC ACTIVITIES OF THE MEDITERRANEAN DEEP-SEA CRAB GERYON LONGIPES AND OF THE PACIFIC HYDROTHERMAL VENT CRAB BYTHOGRAEA THERMYDRON.

Changes in enzymatic activities and protein content of leg muscle and hepatopancreas tissue of two deep-sea crabs were studied after 34 days of food deprivation. Geryon longipes and Bythograea thermydron are the most abundant deep-sea crab species in their respective environment. Geryon longipes dwells on the middle and lower slope of the northwestern Mediterranean Sea and has a bathymetric range between 450 and 1950 m depth. Bythograea thermydron dwells in Pacific hydrothermal vent sites and has a bathymetric range between 2000 and 3000 m depth. After 34 days under laboratory conditions, citrate synthase activities in the hepatopancreas of G. longipes and B. thermydron were found to be much lower in food-deprived crabs compared to fed crabs. In both species, no lactate dehydrogenase activity was detected in hepatopancreas tissue, and no food deprivation effects were observed for either lactate dehydrogenase or citrate synthase activities in leg muscle tissue. No changes in protein were found after 34 days of food deprivation, either. Enzyme activities of fed and food-deprived specimens maintained in the laboratory encompassed the natural range of variation measured in freshly caught crabs of both species. Lactate dehydrogenase, citrate synthase, and protein content of freshly caught specimens of G. longipes were significantly lower than in freshly caught specimens of B. thermydron. The results are discussed taking into account the surrounding environmental features both species encounter and from the point of view of the potential use of citrate synthase activity as an indicator of nutritional condition in deep-sea crustaceans.