Histopathological Changes in the Gills of Oreochromis mossambicus Exposed to Mercury Chloride (HgCl2)

Most of the fish deaths caused by pollutants demonstrate gills damage, since it located outside the body that directly exposed to water as a medium of life, thus this organ is the first to be affected if pollutants contaminated water environment. The objective of this research was to find out histopathological changes of tilapia fish (Oreochromis mossambicus) gills exposed to mercury chloride (HgCl2). This study used 36 male tilapia fish weight of 200-300 grams collected from farmer’s ponds in Cadek, Aceh Besar, which grouped into 4 treatment groups with 3 replications. The fish in PO group was considered as negative control group, while fish in PI, P2, and P3 were exposed to 0.25, 0.50, and 0.75 ppm of HgCl2, respectively, for 10, 20, and 30 consecutive days. Fish were sacrificied to collect the gills then followed by histopathological examination. The results showed that fish in control group (P0) demonstrated normal histological structure of gills containing primary lamella, secondary lamella, interlamellar cell, erythrocyte, and pillar cell. Meanwhile the fish gill exposed to HgCl2 showed several alterations such as edema, congestion, primary and secondary lamella hyperplasia, and secondary lamella fusion in all treatment groups. To conclude, HgCl2 exposure caused gills damage histopathologically, which more severe along with the increasing of HgCl2 concentration and the longer time of exposure.