Physiological and cellular responses of marine medaka fish (Oryzias dancena) to ammonia stress treatment

Abstract

Ammonia is regarded as one of the most widely distributed chemical in aquatic environment as it enters to the aquatic environment by sewage effluents, also is produced by some aquatic organisms and can adversely pose physiological effects to the fish when is in high concentration or allowed to get in to contact with fish a long period of time. In order to understand those effects to fish, marine medaka fish (Oryzias dancena) which is model fish was exposed to ammonia in different concentrations. Adult medaka fish was exposed to 1.5 ppm for 24, 48 and 96 hours and juvenile medaka fish was treated with 0, 4.5, 9.0, 18 and 36 ppm for 48 hours and expression of gill and kidney anti-oxidant enzymes like catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and superoxide dismutase (SOD) were measured using semi quantitative PCR and the result observed showed that the fish (O. dancena) responded by exhibiting expression of target genes as physiological mechanism to protect the body. On the other hand, juvenile medaka fish also responded by showing differences in expression patterns between control group (0ppm) and experiment groups (4.5, 9, 18 and 36 ppm) signifying that ammonia can cause stress to the studied fish.