Histopathological effects of lethal and sub-lethal concentrations of glyphosate on gills and liver of African catfish, Clarias gariepinus

Abstract

The histopathological effects of lethal and sub-lethal concentrations of glyphosate on African catfish Clarias gariepinus were investigated. C. gariepinus juveniles were assessed in a static renewal bioassay for 96 hours (acute toxicity) and 28 days (chronic toxicity) using varying concentrations (0.0 mg/l 20.0 mg/l, 30.0 mg/l, 40.0 mg/l, 50.0 mg/l, and 60.0 mg/l) and (0.0 mg/l, 1.0 mg/l, 2.0 mg/l, 3.0 mg/l, 4.0 mg/l and 5.0 mg/l) of glyphosate respectively. At various concentrations of toxicants, the fish showed abnormal behaviours such as restlessness, lost of balance, respiratory distress, mucous secretion and erratic swimming. A dose-related increase in mortality was observed in fish exposed to lethal concentration with almost 100% mortality after 96 h exposure to highest concentration (60.0 mg/l). The 96 h LC50 obtained was 20.0 mg/l. At the end of experiments, the fish were sacrificed and gills and liver of fish were removed for histological bioassay. The results showed various histological lesions in gills and liver of toxicant exposed fish which was directly proportional to increase in toxicant and exposure period. The study showed that both lethal and sub-lethal concentrations of glyphosate are harmful to Clarias gariepinus. The implication of these results in rational exploitation and conservation of aquatic resources were highlighted.

Keywords: Glyphosate, histology, mortality, toxicity, fish conservation, public health, lethal, sub-lethal