PRELIMINARY STUDIES ON THE EFFECTS OF SALINITY ON INTRACELLULAR NITROGENOUS OSMOLYTES IN VARIOUS TISSUES AND HEMOLYMPH OF THE JAPANESE SPINY LOBSTER, PANULIRUS-JAPONICUS (VONSIEBOLD, 1824)

The Japanese spiny lobster Panulirus japonicus tolerated exposure for 24 h to osmolarities ranging from 760 to 1240 mOsm/l at 20 degrees C. Acute exposure to hypo- and hyperosmotic stress resulted in hyper- and hypoosmotic regulation of hemolymph, respectively, indicating that this species is a stenohaline osmoregulator. Free amino acids and betaines in the muscle, midgut gland, ovary, and gills were measured after the lobsters were exposed to hypo- and hyperosmotic stress for 24 h. Results obtained showed that glycine, glycine betaine and homarine are important osmoeffectors. The decrease in glycine under hypoosmotic condition and the increase in glycine, glycine betaine, and homarine under hyperosmotic conditions were noticeable in the tissues studied: suggesting that these nitrogenous components play a significant role in intracellular osmoregulation. Changes in free amino acids and betaines in the hemolymph during the exposure of lobsters to different osmolarities were opposite to those in the above-mentioned tissues.