Ahmed Th. Ibrahim

Sublethal toxicity of carbofuran pesticide on the African catfish Clarias gariepinus (Burchell, 1822): Hematological, biochemical and cytogenetic response

The present work aimed to evaluate the toxic effects of two sublethal concentrations of carbofuran pesticide (0.16 and 0.49mg/L, for 35 days) on hematological and blood biochemical parameters of catfish, Clarias gariepinus, and to evaluate the genotoxic potential of carbofuran on the erythrocytes of C. gariepinus for the first time by micronucleus and erythrocyte alteration assays. The results revealed a significant (p<0.05) decrease in red blood cells (RBCs) count, haemoglobin (Hb) concentration, haematocrit (Hct) and the mean corpuscular haemoglobin concentration (MCHC) levels, but the mean corpuscular volume (MCV) and the mean corpuscular haemoglobin (MCH) levels were increased. White blood cells (WBCs) count, neutrophils, eosinophils, basophils and monocytes were increased significantly (p<0.05), while the lymphocytes were decreased. Also, carbofuran exposure caused a significant (p<0.05) increase in aspartic aminotransferase (AST) and alanine aminotransferase (ALT) and a significant (p<0.05) decrease in alkaline phosphatase (ALP) activity. The results obtained showed a significant (p<0.05) increase in plasma glucose, total lipids, urea and creatinin levels, but the total protein, albumin concentration and globulin levels were decreased (p<0.05) significantly and consequently A/G ratio also decreased. Carbofuran caused many genotoxic and morphological alterations in erythrocytes such as formation of micronuclei (MN), echinocytes, acanthocytes, tear like drop cells, microcytes and erythrocytes with vacuolated cytoplasm and pale nucleus. The exposed groups have shown significant variations in frequencies of MN and altered erythrocytes in comparison to control group, and these frequencies increased significantly (p<0.05) with the increase of carbofuran concentration. Therefore, current results present a clear evidence of the response of C. gariepinus to carbofuran and allow us to consider that C. gariepinus as a good bioindicator to reflect the toxicity and the genotoxic potential of carbofuran that might be released into the aquatic ecosystems.

Sublethal toxicity of carbofuran on the African catfish Clarias gariepinus: Hormonal, enzymatic and antioxidant responses

The present study examined the impacts of carbofuran on endocrinology of the catfish, Clarias gariepinus, for the first time and evaluated cortisol (CRT), triiodothyronine (T3), thyroxin (T4), 17β-estradiol (E2) and testosterone (TST) and the oxidative stress markers including SOD, CAT, GSTs, GSH. The toxic effects on the metabolic enzymes, G6PDH and LDH, in addition to lipid peroxidation (LPO) and DNA damage as biomarkers in Nile catfish, to sublethal exposures of carbofuran (0.16 and 0.49mg/L, for 35 days) were studied. Statistically significant differences between selected parameters between control and carbofuran-treated fish were recorded. Carbofuran caused a significant (p<0.05) increase in CRT and T3 levels; the mean levels of T4, TST, E2 exhibited significant decreases (p<0.05) in carbofuran-treated fish. Toxicity of carbofuran on liver, kidney, gills, gonads and muscles after 35 days of exposure was found. Glycogen levels showed a highly significant decrease in liver and gills (p< 0.001), a significant decrease (p< 0.05) in kidney and muscles, and insignificant changes (p>0.05) in gonads of treated fish. The two metabolic enzymes G6PDH and LDH in all tissues exhibited significant decreases (p<0.05) in treated fish. SOD, CAT, GSH and GST levels showed significant decreases (p<0.05) in all tissues of fish after exposure to carbofuran. LPO levels increased significantly (p<0.05) in all tissues except gonads after 5 weeks of exposure to carbofuran. There was a significant (p<0.05) increase in DNA fragmentation percentage in treated fish. Our results provide a clear evidence on the response of C. gariepinus to sublethal doses of carbofuran and allow us to consider catfish as a good bioindicator to reflect the endocrine disrupting impacts of carbofuran, and reflect the potential of this pesticide to cause disturbance in antioxidant defense system as well as metabolism and induction of lipid peroxidation (LPO) and DNA damage in contaminated ecosystems.

Biochemical response of the African catfish, Clarias gariepinus (Burchell, 1822) to sublethal concentrations of mercury chloride with supplementation of selenium and vitamin E

The present investigation aimed to determine the toxicological effects of mercury chloride on biochemical parameters of the widely consumed African catfish, Clarias gariepinus. Adult specimens of Clarias gariepinus were exposed to sublethal concentrations (0.04 and 0.12 ppm) of mercury chloride for 7, 14, 21 and 28 days. Empirical data of results obtained were subjected to statistical analysis of variance (ANOVA) to test the effects of mercury, selenium, vitamin E and exposure periods. The mean values of Na+, Urea, Creatinine, AST, ALT and ALP were significantly increased from the control values, while mean values of K+, Glucose and Triglyceride were significantly decreased from the control values. Selenium and Vitamin E supplementation play appositive role in detoxification of mercury toxicity specially the low dose. The results suggest that mercury chloride can negatively affect the physiology of fish. It was observed that supplementation of selenium and vitamin E decreases the toxic effect of mercury.