en تخصصي Special پژوهشي Research <strong>Background:</strong> Histological studies in organs like hepatopancreas and gill of the freshwater fish, <em>Cyprinus carpio, </em>were made to assess tissue damage due to sub-lethal concentration of cadmium after a long exposure period.<br> <strong>Methods:</strong> This study was conducted in University of Tehran, in 2013. The fish were divided into two groups in 1000 litre fiberglass tanks supplied with dechlorinated water [hardness 302.6 mg CaCo₃/l, pH 7, O₂ 7.8 mg/L and temperature 15 &plusmn; 2 &ordm;C] and continuous aeration. Group 1 was without any cadmium considered as control group. Group 2 was exposed to 30 ppb CdCl₂ (Merck) containing 7.8 ppb cadmium. The tissue samples from: hepatopancreas, gill were collected 30 days post exposure and processed by histological procedures.<br> <strong>Results:</strong> The main lesions in cadmium exposed groups were: (a) pancreatitis necrosis in endocrine part of pancreas (b) cholangitis and necrosis in liver parenchyma (c) hypertrophy, fusion and telangiectasia in secondary lamellae<br> <strong>Conclusion:</strong> Cadmium chloride at low concentration can induce pathological alterations in hepatopancreas and gill of common carp. کادمیوم, هپاتوپانکراس, اثرات بافتی, کپور معمولی, آبشش Cadmium, Common Carp, Gill, Hepatopancreas, Histological Effects 1 4 http://ijt.arakmu.ac.ir/browse.php?a_code=A-10-397-1&slc_lang=en&sid=1 Farzad Ghiasi فرزاد غیاثی f.ghiasi@uok.ac.ir 10031947532846006461 10031947532846006461 Yes Department of Fisheries, Faculty of Natural Resources, University of Kurdistan, Sanandaj, Iran. دا نشگاه کردستان Seyed Saeed Mirzargar سعید میرزرگر 10031947532846006462 10031947532846006462 No Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. دانشگاه تهران Javad Ashrafihellan جواد اشرفی هلان 10031947532846006463 10031947532846006463 No Department of Pathology, Veterinary college, University of Tabriz, Tabriz, Iran. دانشکده دامپزشکی-دانشگاه تبریز