Effect of prolonged exposure and withdrawal of methyl-tert-butyl ether on some haematological and haemopoietic parameters of the Nile catfish clarias gariepinus [Burchell, 1822]

ABSTRACT

The present study is an attempt to evaluate the long - term effect of a sublethal concentration of Methyl-tert- butyl ether on the haematology as well as the spleen as a major haemopoietic organ of the catfish Clarias gariepinus. It also emphasizes the possibility of MTBE biodegradation in fishes after its withdrawal from the aquatic medium. The experiment was carried out on three groups of adult Clarias of both sexes for 2 months. Group [I] served as a control group. Group [II] of fish were subjected to 1054 mg/l MTBE for 2 months, while group [III] represents the recovery group of fish maintained in clean water after withdrawal of the pollutant for another 2 months. The results indicated variable changes in haematological parameters of treated fishes. These changes included decrease in RBCs count, Hb content and HT%. Also, thrombocytopenia was obvious from the decrease of platelets number. On the other hand, the increase of the WBCs count indicated leucocytosis in treated fish. The increase of different red blood cell indices [MCv, MCH and MCHC] identified the anemia developed in treated fish as macrocytic hyperchromic anemia. Histological lesions were manifested by an increase of connective tissue and hyaline material, dilatation and congestion of blood vessels and thickened splenic arteries. Degeneration, necrosis, inflammatory infiltration and pyknotic nuclei were prominent features of the splenic tissue. Proliferations of reticulin fibres were noticed in splenic pulp, trabeculae and blood vessels. Histochemical study implied augmentation of haemosiderin pigments in MTBE treated fish. No significant improvement was recorded in all studied blood parameters nor in splenic tissue upon MTBE withdrawal from H2O2 for 2 months. In conclusion, the decline in different blood parameters have gone hand in hand with a corresponding destruction of the spleen tissue after MTBE prolonged exposure. The irreversible damage proved the inhibitory action of MTBE on the haemopoietic tissue of Clarias. The use of such toxicant must be under regulatory control