Effects of Ambient Ammonia‐Nitrogen Exposure on Uric Acid and Urea Metabolic Pathways and Tissue Distribution in the Swimming Crab Portunus trituberculatus.

This article focuses on the effects of ammonia-nitrogen (ammonia-N) exposure on nitrogen metabolism in the swimming crab Portunus trituberculatus, a species important to aquaculture. The study found that elevated ammonia-N levels increased hemolymph ammonia content and altered the expression of key enzymes involved in nitrogenous waste metabolism, including xanthine oxidase (XO) and uricase (URI) related to uric acid metabolism, and carbamoyl phosphate synthetase III (CPSIII) and arginase (ARG) involved in urea synthesis via the ornithine–urea cycle (OUC). Uric acid was primarily stored in muscle tissue, while urea was mainly synthesized in the hepatopancreas and released into the hemolymph, with urea levels significantly exceeding those of uric acid under ammonia stress. These findings suggest that swimming crabs detoxify excess ammonia not only through direct excretion but also via conversion to uric acid and urea, providing a basis for further research on nitrogen metabolism and ammonia detoxification mechanisms in crustaceans.