en Toxicology and polution Toxicology and polution پژوهشي Original research papers <p>&nbsp; Sublethal toxicity effects of diazinon on the structure of some organs of great sturgeon ( <i>Huso huso </i>) were investigated. Diazinon was applied at a sublethal concentration of 1.5 mg L -1 at 22&plusmn;1 &ordm;C for nine weeks as a constant bath. Tissues of liver, kidney and gills were sampled and examined histopathologically&nbsp;&nbsp; after 1, 14, 28, 42 and 63 days post exposure to the toxicant. The results of light microscopic examinations of tissues revealed congestion of blood vessels, pyknosis and cloudy swelling in hepatocytes. Congestion of blood vessels and thickening of the basal membrane of bowman capsule in&nbsp;&nbsp; glumerol of the kidney were also observed. The gill of fish exposed to toxicant also showed congestion&nbsp;&nbsp; and dilation of blood vessels, swelling of the basement membrane, hyperplasia, fusion and necrosis of&nbsp;&nbsp; lamellae. This data showed that a long term exposure of fish to diazinon can cause several pathological&nbsp;&nbsp; changes in respiratory organ, haematopoietic tissues and liver.</p> diazinon, great sturgeon, sublethal 27 35 http://ijaah.ir/browse.php?a_code=A-10-35-14&slc_lang=en&sid=1 I. Sharifpour 1003194753284600931 1003194753284600931 No Iranian Fisheries Research Organization, Tehran, Iran H.A. Khosbavar Rostami 1003194753284600932 1003194753284600932 Yes Inland Waters Aquatic Stocks Research Center, Gorgan, Iran A. Mokarami-Rostam 1003194753284600933 1003194753284600933 No The Caspian Sea Ecology Research Center, Sari, Iran