The effect of mercury chloride in different salinities on the histopathology of juvenile oreochromis niloticus

The increased concentration of heavy metals, especially mercury chloride, in the aquatic environment results in toxicity for the life of aquatic organisms, including Nile tilapia (Oreochromis niloticus L.). This study aimed to determine the histopathological damage of heavy metal mercury (Hg) exposure in different salinities to juvenile Nile tilapia. The research method was an experimental study with a Completely Randomized Design (CRD), using five different treatments with three replications. The histopathological damage of the gill and skin of Nile tilapia were determined. Data analysis conducted in this study consisted in the Kruskal-Wallis test with the reflection scoring method and continued with the Mann-Whitney U test. The results of histopathological examination of the gills and skin showed damage in the gills, including edema, hyperplasia, hemorrhage and necrosis. The highest damaging effect of mercury chloride exposure on gills, especially hyperplasia, was in treatment A, with 0 ppt salinity and 0.016 mg L^-1 of chloride. Meanwhile, the histopathological observations in the skin did not show significant differences between treatment groups. Mercury chloride exposure in different salinities had an effect on the histopathological damage of gill organs and the skin of Nile tilapia. The results also showed the potential of salinity to suppress the toxicity of mercury chloride and prevent damage to the gills and skin of Nile tilapia.