Haemolymph 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), 1.011, 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 relationship with concentration of ambient ammonia-N.3. Shrimp exposed to 10.032 mg/l ammonia-N after 24 hr significantly affected (P < 0.05) haemolymph PCO₂ 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 pattern, and may cause catabolism of hemocyanin and protein to free amino acids to balance osmoregulation.