Fenthion is one of the most widely used organophosphate insecticides for the control of many varieties of pests in Nigeria. The genotoxic effect of the pesticide was evaluated in the blood erythrocytes of Clarias gariepinus using the micronucleus (MN) test. The oxidative stress parameters were also studied in the liver and gill tissues. Fish were exposed to 2.0, 4.0, and 8.0 mgL of fenthion and sampling was done on days 1, 7, 14, 21 and after 7-day recovery. Micronuclei induction was highest (7.55) on day 14 at all concentrations in the peripheral blood cells. Oxidative stress was evidenced by increased lipid peroxidation (LPO). Maximum LPO values of 62.47% and 71.17% were observed in the gill and liver tissues respectively in C. gariepinus exposed to 8.0 mgL concentration of fenthion. There were alterations in the values of reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) during the exposure and recovery periods. The 7-day recovery period was not adequate to eliminate fenthion-induced changes as LPO, CAT, and GR activity remain elevated. However, MN frequency and activity of SOD, GSH, and GPx (except at 8.0 mgL) recovered. The present findings give further credence on the integrated use of MN test and oxidative stress parameters in risk assessment of pollutants in aquatic ecosystem.
A 60-day study was conducted to investigate the dietary effect of replacement of maize with graded levels of melon shell meal (MSM) on growth performance of Clarias gariepinus fingerling. Five isonitrogenous diets were formulated. MSM was added to the diet to replace maize at graded levels; 0%, 25%, 50%, 75% and 100%. Total of 150 fish (3.40±0.05g) were randomly assigned to the five treatment diets. Each treatment contained 10 fish per tank and each treatment was triplicated in a completely randomised design (CRD). Fish were fed twice daily at 5% body weight in equal proportions. Results showed significant differences (P<0.05) for measured growth parameters. Fish fed diet containing 100% MSM had the highest mean weight gain (70.70±4.62g), specific growth rate (SGR) (5.06±0.10%), best feed conversion ratio (FCR) (0.54±0.04%) and protein efficiency ratio (PER) (1.68±0.11%) compared to other treatments and the control while fish fed 25% MSM had the poorest values for MWG (39.88±4.37g), SGR (4.20±0.16), FCR (0.60±0.02) and PER (0.95±0.11). MSM inclusion in diet of C. gariepinus up to 100% enhanced growth.
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