Alterations in gills and intestine of Danio rerio after exposure to acaricide yoksorrun-5EC (hexythiazox): histopathologic and morphometric evaluation

Abstract

In this study, histopathological and morphological changes in gill and intestinal tissue of zebra fish exposed to acaricide yoksorrun were aimed to determine. Yoksorrun was applied to the experimental groups as 0.01 mL/L, 0.02 mL/L, and 0.03 mL/L. Histopathological findings which showed a parallel increase with the amount of exposure in the gill were determined. In the gills, disruption of lamellae shape, shortening and breakage of primary and secondary lamellae, edema, fusion, and separation in the secondary lamellae epithelium, hyperplasia were observed. In the intestine tissue of some groups, advanced necrosis at the tip of the villi and deterioration of the overall integrity of the villi in these regions, epithelial hyperplasia, increasing in eosinophilic cells in the submucosa, and dissolution in muscle fibers of tunica muscularis were observed. In the morphometric analysis of the gills, a significant decrease in gas exchange (PAGE) percentages (p < 0.0001) was observed in the experiment group compared to the control group. Compared to the control group, a significant decrease in the interlamellar distance and secondary lamellar length measurements of the gills and a significant increase in the secondary lamellar width measurement were observed. In basal epithelial thickness measurement, the result was insignificant between the groups. According to the results of the morphometric analysis of the intestine, a significant decrease in musculus externa was observed only in the group 2. In total wall thickness, there was a significant thinning (p < 0.0001) in all experimental groups. There was a significant shortening of the villi length (p < 0.0001) and a significant increase (p < 0.0001) in the villus width only in the group 2 and group 3. A significant increase in epithelial thickness after application was observed (p < 0.0001) in all groups compared to the control group. Based on the findings, it was decided that the living in the aquatic ecosystem would be adversely affected by this acaricide if exposed.