Histological and hematological changes to Clarias gariepinus juveniles exposed to acute doses of Emamectin benzoate in a static bioassay.

Emamectin benzoate (EMB) is a potent neurotoxic pesticide, extensively used in agriculture and aquaculture in Nigeria. The knowledge of its toxicological impact to C. gariepinus in Nigeria is scarce. Thus, the investigation was designed to uncover its 96 h LC50, safe level to aquatic media, histological impact on fish liver, gill and hematological changes in the blood parameters. 96 h LC50 was 0.34 mg L-1. Safe level of EMB was 0.034 mg L-1. Dose dependent liver degenerations were characterized by; Congestion of the central vein by inflammatory cells, pyknotic nuclei of hepatocytes, coagulation necrosis, focal necrosis, dilations of sinusoidal spaces and infiltration of periportal regions by inflammatory cells. Dose dependent changes in gill were characterized by; mucus secretion, shrinkage of secondary lamellae, hyperplasia, occlusion of secondary lamellae, degeneration of gill cartilage, necrosis of respiratory epithelia and erosion of secondary lamellae. Red blood cell indices decreased minimally at the end of the 96 h exposure. White blood cell count (WBCC), mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were significantly (p ≤ 0.05) elevated in three treatments. Neutrophils decreased significantly (p ≤ 0.05), basophils, eosinophils and monocytes showed mixed tendencies. The findings of this investigation imply that C. garipinus exposed to EMB may cause dose and time-dependent changes in the liver and gill histology as well as alterations in the fish's hematological profile, all of which were harmful to the fish's health. To avoid negative effects on fish in nearby aquatic settings, it is advised that the use of EMB be monitored and limited.

Genotoxicity assessment and oxidative stress responses in freshwater African catfish Clarias gariepinus exposed to fenthion formulations.

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-1 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-1 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-1) 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.

Oxidative stress, biochemical, lipid peroxidation, and antioxidant responses in Clarias gariepinus exposed to acute concentrations of ivermectin.

The short-term effects of ivermectin (IVMT) on the oxidative stress and biochemical parameters of Clarias gariepinus juvenile was assessed under semi-static conditions at concentrations of 9 to 25 µg L-1 for up to 4 days. Juveniles were highly sensitive to ivermectin, with an LC50 of 15 µg L-1.The antioxidant enzyme profile assessed included glutathione reductase (GR), superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). General stress biomarkers such as serum glucose, protein, alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were also determined at 24-h, 48-h, 72-h, and 96-h exposure durations. Lipid peroxidation showed significant (p < 0.05) decreases in higher concentrations (21 µg L-1and 25 µg L-1) and durations of exposure (72 h and 96 h). Significant concentration-dependent increases (p < 0.05) were recorded in the liver function enzymes, superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR) when compared to the control. GPx decreased significantly (p < 0.05) in higher concentrations (21 µg L-1and 25 µg L-1) and durations of exposure (48-96 h). Protein showed significant concentration-dependent decreases, while glucose recorded a mixed trend. The changes in the hepatic antioxidant enzyme activities and serum metabolites were indicative of oxidative stress induced by IVMT. This showed that IVMT is toxic to fish and should be used with utmost caution.