Histological changes in liver, kidney, gills, and retina following exposure of cadmium and mercury in Zebrafish

In the study, histopathological evaluation of liver, kidney, gills and retina of adult female zebrafish was carried out following individual exposure to CdCl₂ (1 mg/L) and HgCl₂ (30 μg/L) as well as combined exposure to CdCl₂ (1 mg/ L) + HgCl₂ (30 μg/L) for 21 days. Exposure of zebrafish to HgCl₂ resulted more histological changes in the liver as compared to that caused by CdCl₂ alone and in combination. In kidney, combined exposure caused more severe microscopic lesions compared to individual exposure of Cd and Hg. Near to similar histopathological lesions in the gills of fish exposed to Cd, Hg and Cd + Hg were noticed which indicate the sensitivity of gills towards concentration of metals in the water. Combined exposure group exhibited marked degenerative changes in choroid, retinal pigmented layer and photoreceptor layer of retina of zebrafish as compared to individual exposure groups. In conclusion, exposure to binary mixture of Cd and Hg causes noticeable changes in gills and retina as compared to liver and kidney which might be due to toxic effects of metals through direct contacts.