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

Abstract

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.