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 th is species is a stenohaline osmoregulator. Free amino acids and betain es in the muscle, midgut gland, ovary, and gills were measured after t he lobsters were exposed to hypo- and hyperosmotic stress for 24 h. Re sults obtained showed that glycine, glycine betaine and homarine are i mportant osmoeffectors. The decrease in glycine under hypoosmotic cond ition and the increase in glycine, glycine betaine, and homarine under hyperosmotic conditions were noticeable in the tissues studied: sugge sting that these nitrogenous components play a significant role in int racellular osmoregulation. Changes in free amino acids and betaines in the hemolymph during the exposure of lobsters to different osmolariti es were opposite to those in the above-mentioned tissues.