A Comparative Study of Toxic Effect of a Euphorbia’s Plant Euphorbia tirucalli Against Two Freshwater Harmful Snails in Laboratory as Well as in Pond and its Effect on Their Reproductive Physiology

In the present study molluscicidal activity of methanol extract of stem bark of plant Euphorbia tirucalli (Family: Euphorbiaceae) against two freshwater harmful snails Lymnaea acuminata and Indoplanorbis exustus were evaluated in the laboratory as well as in the pond. Both snails are intermediate hosts of liver fluke, Fasciola hepatica and Fasciola gigantica, which causes endemic fascioliasis in cattle and livestock. Toxicity experiment was performed by the method of Singh and Agarwal (1988). The toxicity of methanol extract was time as well as dose dependent and there was a significant negative correlation between LC values and exposure periods, thus the LC value of methanol extract was decreased from 8.18 mg/L (24h) to 3.43 mg/L (96h) in the 50 case of Lymnaea acuminata and from 10.24 mg/L (24h) to 5.06 mg/L (96h) in the case of snail Indoplanorbis exustus in laboratory. Similar trends of toxicity were also observed in the case of pond but the toxicity of methanol extract was lowered about 3.0-4.7 times in pond than the laboratory. The LC (24h) doses of methanol 90 extract against snail have no apparent killing against non target organism i.e. fish Channa puctatus in the treatment of mixed population of snail and fish which shares the habitat of these snails. The effects of different sub lethal concentration of this extract on the reproductive physiology of both the snails i.e. Lymnaea acuminata and Indoplanorbis exustus were performed up to 28 days in laboratory. Concentration-dependent effects of this extract on snail’s embryogenesis were noted. It was found that fecundity, hatchability and survivability was significantly reduced and no survival was observed at higher dose after 28 days in the snail L. acuminata. Hence it can be concluded that methanol extract of plant E. tirucalli was toxic against all the stages of both the snails and acts as potential source of safer molluscicides.