The Effect of Zinc Concentration on Physiological, Immunological, and Histological Changes in Crayfish (Procambarus...

The release of heavy metals to the environment increased dramatically with industrialization and rapid economic development, and they have accumulated in aquatic organisms. The current study aimed toe valuate the physiological, immunological, and histological changes of crayfish (Procambarus clarkii) as bio-indicator for water quality. Crayfishes of the filed study group were collected from a polluted area (Rosetta branch, Egypt), where the highest concentration for heavy metals in water was for zinc (Zn). Besides the field study group, other crayfishes were exposed to different doses of ZnSO₄ (0, 203, and 406 mg L^-g) corresponding to Zn concentration (0, 46.03, and 92.06 mg L^-1) respectively in aquariums for consecutive 4 days. Heavy metal concentrations in field water sample were arranged as follows: Zn > Fe> Pb > Cu and Mn > Ni > Co > Cd. The result revealed that Zn bioaccumulation increases significantly with the increase of water Zn concentration among the tested groups compared to the control group, where the highest bioaccumulation in all studied tissues (hepatopancreas, gills, and muscles) was observed in the field group and Zn high-dose group. Also, there was a significant increase in the levels of hemolymph uric acid, urea, creatinine, glucose, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase. Their highest concentrations were observed in the Zn high-dose group and the field group, while the levels of total protein, albumin, and cholesterol showed a significant decrease among the tested groups as compared with the control group. Their determined lowest concentrations were in the Zn high-dose group and field group. Among tested groups, total hemocytes and granulated hemocytes decreased significantly while hyaline hemocytes increased as compared with the control group. Histological damages were observed in hepatopancreas, gills, and muscles in the field and Zn groups. The present study showed that exposure to Zn caused physiological and histological changes in Procambarus clarkia. We assumed that Procambarus clarkia could be used as a sensitive bioindicator for monitoring water quality criteria.