To study the effects of mercuric chloride on kidney and intestine tissue of Persian Sturgeon, Acipenser persicus fry, fish exposed freshwater contain 15 ppb of mercuric chloride and control group were kept in non polluted freshwater for 48 hours. Histological studies of the processed tissues showed marked histological alterations than the control group that exposed only to freshwater. The pathologic lesions of the kidney included severely epithelial cell necrosis, lesion of epithelial cells from the basement membrane in the proximal and distal tubules. Proximal tubule also showed inflammation and incorporation of brush borders. Decrease of lymphoid and hematopoietic tissue observed. Pathologic lesions of intestine tissue were showed the epithelial necrosis, shrinkages of secretory follicule, lesion of epithelial microvilli in intestine. Results showed that low concentration of mercuric chloride can pose undesirable alternation in Persian Sturgeon fry, an economic and endangered species of the Caspian Sea
