Effects of ammonia exposure on nitrogen metabolism in gills and hemolymph of the swimming crab Portunus trituberculatus

• Rh protein mRNA expression level was up-regulated in gills.
• Ammonia can be converted togln and urea in Portunus trituberculatus.
• Gln and urea contents in hemolymph could be proposed as suitable physical indexes.

The effects of ammonia-N (control, 1 and 5 mg L− 1) on nitrogen metabolism in gills and hemolymph of the swimming crab Portunus trituberculatus were investigated. The results showed that mRNA expression levels of Rh protein in gills were induced significantly by ammonia-N exposure. The levels of glutamine (Gln) and urea increased significantly in gills and hemolymph of P. trituberculatus exposed to high ammonia-N. After high ambient ammonia-N exposure, hemolymph ammonia increased significantly at 6 h and declined to control level at 12 h. The levels of Gln and urea in gills and hemolymph were significantly higher than control group during the whole exposure period and showed dose and time dependent effects. In addition, the activities of key-related enzymes involved in biosynthetic pathways of Gln and urea such as glutamate dehydrogenase (GDH), glutamine synthetase (GS) and Arginase (ARG) increased remarkably in the present study. This suggests that P. trituberculatus possesses some ammonia-detoxification strategies to cope with high ambient ammonia, including an up-regulation of Rh protein in gills and conversion ammonia to Gln and urea. The levels of Gln and urea in hemolymph could be considered as suitable physical indexes to evaluate ammonia toxicity to serve anti-ammonia selective breeding in the long run.