Contribution to the study of the changes in the gills of zebrafish (Danio rerio) when exposed to dioxin

Abstract

       This study determined cell changes in the gills of zebrafish (Danio rerio, Hamilton, 1822) as a result of a dietary supply of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). 50 zebrafish were divided into five groups, one control group and four experimental ones. The experimental groups were supplied 10, 40, 100 and 270 ng/day/fish TCDD, respectively. Structural, ultrastructural and morphometric studies of the fish gill were carried out, indicating that, in low concentrations, fish gills presented hyperemia with progressive erosion of the endothelium of the capillaries resulting in edema and microhaemorrhages. In the non-respiratory gill, in those groups with low concentrations, it could be observed that the chloride cells presented hypertrophy as a result of dilatation of the intracellular canal and swelling of the microvilli, losing their activity in the degradation of chemical substances (according to some authors) in those groups with a higher concentration. Mucous cells presented hyperplasia and hypertrophy. The sensory buds were not directly affected, but, due to the
presence of interstitial edema, swelling of the supporting cells occurred without the involvement of the neurosensory cells. We concluded that dioxins affect the gills to a greater or lesser extent depending on their concentration in the fish’s diet, which alters their functionality.