HEMOLYMPH OSMOLALITY, ACID-BASE-BALANCE AND SHIFT OF AMMONOTELIC TO UREOTELIC EXCRETORY PATTERN OF PENAEUS-JAPONICUS EXPOSED TO AMBIENT AMMONIA

1. Urea-N and nitrite-N excretions of Penaeus japonicus (11.70+/-2.30 g) increased, but ammonia-N excretion decreased with increased ambient ammonia-N, as they were exposed individually to 0.055 (control), 1.01 1, 5.121, 10.032 and 20.335 mg/l ammonia-N after 24 hr. 2. Haemolymph pH, PCO2 and osmolality of shrimp displayed an inverse linear relation ship with concentration of ambient ammonia-N. 3. Shrimp exposed to 10. 032 mg/l ammonia-N after 24 hr significantly affected (P<0.05) haemoly mph PCO, and osmoregulatory capacity. 4. Accumulated ammonia-N in the haemolymph of shrimp following exposure to ambient ammonia-N at 5.121 mg/l or greater caused a shift from an ammonotelic to a ureotelic patt ern, and may cause catabolism of hemocyanin and protein to free amino acids to balance osmoregulation.