Determination of diazinon LCso in Grass carp (Ctenopharyngodon idella) and the effect of sublethal concentration of toxin on some hematological and biochemical indices

Toxicity of the organophosphate, diazinon was studied in grass carp(cetenopharyngodon idella) weighing 5±1.0g, under static water quality conditionat 16°c. also, some hematological and biochemical variables of fish weighing509plus-minus)5.0g were studied 12 hours post-exposing fish to the toxicant at sublethalconcentration of 5.6mgll at 16°c. values of 18.19,17.21,16.68, and 15.13mg/l,were obtained as lcso after 24, 48, 72 and 96 hours post-exposing fish to thetoxicant, respectively. levels of red blood cells (rbc), hematocrit (pcv),hemoglobin (hb), mean corpuscular hemoglobin concentration (mchc),leukocyte count (wbc), lymphocyte and monocyte were significantly lower in the exposed fish than control fish (p(less than)o.05), whilst values of polymorphonuclear cells(pmn) and myelocytes counts were higher in the test group (p(less than)o.05). in addition,the levels of aspartate aminotransferase (ast), alkaline phosphatase (alp) andlactate dehydrogenase (ldh) were significantly lower in fish exposed to thetoxicant (p(less than)o.05), while the level of alanine aminotransferase (alt) was higher inexperimental fish (p(less than)o.05) than control fish. the levels of glucose and triglyceridewere higher in fish exposed to toxicant than control fish. however, suchdifferences were only significant for glucose level (p(less than)o.05). in contrast, the levelsof total protein and cholesterol decreased insignificantly in fish exposed to thetoxicant compared to those in control fish (p(greater than)o.05). the obtained resu its show thatalthough diazinon can be classified as a slight toxic chemical for grass carp. thetoxicant negatively affects some immunophysiological functions of the fishincluding immunocompent cells.