Acute Toxicity of Calotropis Procera Latex to Clarias gariepinus Juveniles

Acute toxicity of the latex of C. procera on Clarias gariepinus juveniles was measured over a period of 96-h as a management tool in killing predatory fish in earthen ponds in Nigeria. The latex concentrations of 0.0 mg/l, 10.0 mg/l, 22.0 mg/l, 45.0 mg/l, 100 mg/l, 220 mg/l and 1000 mg/l were used under laboratory conditions in plastic aquaria. The 96 h Lc₅₀ was 64.0 mg/l obtained using graphic and probit methods. The regression equation for the probit curve was y = 2.46x + 0.58 (where probit value = Y, X = log concentration per treatment). Behavioral changes observed during exposure of fish to toxicant include hyperactivity, erratic swimming, imbalance coupled with loss of co-ordination, inclination at the water-air interface, increased opercular beats, clustering and crawling and submergence coupled with paralysis (death). De-pigmentation of the skin increased with increase in latex concentration with a complete bleaching from black/dark brown to pure white occurred at 45.0 and 100.0 mg/l. Histological changes included congestion, haemorrhage, multiple foci of spongiosis of white matter, necrosis and cellular infiltration in the brain tissues. Liver exhibited degeneration, fatty change and infiltration, and generalized haemorrhage. Gill showed congestion of capillaries, keratinization, stunting, necrosis and cell infiltration. The heart-tissues were indifferent to treatments. Histological effects increased in intensity with increase in the concentration of C. procera latex.