International Journal of Natural Resources and Marine Sciences 2011, 1 (1), 23-32 23 Histopathological and Pathomorphological Effects of Mercuric Chloride on the Gills of Persian Sturgeon, Acipenser persicus, Fry Zahra Khoshnood, Saber Khodabandeh * , Mohsen Shahryari Moghaddam and Saeedeh Mosafer Khorjestan Department of Marine Biology, Faculty of Marine Sciences, Tarbiat Modares University, Noor, Mazandaran, Iran. Received: 14 September 2010 / Accepted: 14 November 2010 / Published Online: 20 February 2011 Abstract Histopathological and pathomorphological effects of 15 ppb mercuric chloride on Persian sturgeon, Acipenser persicus, were investigated using histological and electron microscopy observations. Light microscopy showed that the gill epithelial hypertrophy, wrinkling and hyperplasia in lamellar epithelia and lamellae fusion occurred after 48 h of exposure. Gill epithelia also showed occasional necrosis, which had almost been completed and blood emerged from the capillaries. However, occasional necrosis in some regions of the filament, both with blood emerging and with no bleeding, was observed by using electron microscopy. These injuries were well observed in inter-lamellar regions of the filament and also wrinkling of the lamellar epithelium. Ultrastructural observations showed some cellular disorders in gill epithelium of the Persian sturgeon, A. persicus, fry. In addition, increase in apical vesicles of the chloride cells and necrosis in apical surfaces of some chloride cells, hypertrophy and necrosis of the chloride cells’ mitochondrion and endoplasmic reticulum also were some of the other cellular disorders observed through transmission electron microscopy. In conclusion, the gills of A. persicus fry were sensitive to low concentrations of inorganic mercury (HgCl 2 ). Key words: Acipenser persicus, Fish, Ggill, Histopathology, Mercuric chloride, Pathomorphology 1 INTRODUCTION Heavy metals are introduced into the marine environment in a number of ways. They may be deposited in the sea ‘naturally’ as a consequence of erosion from ore-bearing rock, windblown dust, volcanic activity and forest fires. Increasingly, however, they are introduced via contaminated rivers, marine outfalls and through the deliberate dumping of wastes in coastal waters (Schindler, 1991; Agusa et al., 1994). Mercury pollution in aquatic ecosystems has received a great deal of attention since the discovery of mercury as the cause of Minimata disease in Japan in the 1950s (Allen et al., 1988). The fate of mercury in the environment depends on the chemical form of mercury released and the environmental conditions. Elemental mercury, inorganic mercury and methyl-mercury are the three most important forms of mercury in natural aquatic environments. Most mercury is released into the environment as inorganic mercury, which is primarily bound to particulates and organic substances and might not be available for direct uptake by aquatic organisms (Beckvar et al., 1996). Toxicity is influenced by the form of mercury, environmental media, environmental conditions, sensitivity or tolerance of the organism, and its life history stage. Inorganic mercury is less acutely toxic to aquatic * Corresponding author: S. Khodabandeh, P.O. Box 46417-76489, Department of Marine Biology, Faculty of Marine Sciences, Tarbiat Modares University, Noor, Mazandaran, Iran. Tel: +98 122 625 3101. Fax: +98 122 625 34 99. E-mail: surp78@gmail.com Downloaded from ecopersia.modares.ac.ir at 1:35 IRST on Monday December 6th 2021