STUDIES ON THE MOLLUSCICIDAL ACTIVITY OF SOLANUM MAMMOSUM AND THE BIOLOGY OF FOSSARIA CUBENSIS (GASTROPODA) (LYMNAEA, MOLLUSCICIDE)

This study deals with the isolation of glycoalkaloids from Solanum mammosum, their action upon Biomphalaria glabrata and Fossara (=Lymnaea) cubensis and the biology of the latter. Alcoholic soxhlet extracts of S. mammosum fruit were found to contain glycoalkaloids, as suggested by froth formation, hemolysis and precipitation with Mayer's, Dragendorff's and Wagner's reagents. Specifically solasonine and solamargine were isolated from fruit extract by fractionation on neutral alumina columns with moist butanol as a solvent. Ethanolic, methanolic or saline extracts of S. mammosum yellow fruit were shown to contain the most potent molluscicides against B. glabrata and F. cubensis, while distilled water extracts contained slightly weaker toxicants. Only yellow and yellow green fruit showed molluscicidal activity strong enough to kill fish and Schistosoma mansoni cercariae below molluscicidal level. Fruit soxhlet extracts of S. mammosum were approximately twice as toxic against B. glabrata under simulated stream conditions as they were under standing water conditions. Time-concentration relationship calculations suggest that optimum exposure time to kill snails under field conditions is 24 hrs and that prolonged applications of low doses of extracts did not affect egg laying of B. glabrata. No statistically significant difference in toxicity of S. mammosum pulp extracts to young and mature B. glabrata found but newly hatched snails were slightly more susceptible.;A practical laboratory technique for mass cultivation of F. cubensis was developed. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI;The mode of action of the fruit extracts and glycoalkaloids was partially investigated. When these agents were mixed with cholesterol, toxicity was reduced, suggesting that glycoalkaloids may combine with cholesterol. It is therefore possible that the glycoalkaloids combine with cholesterol in cell or organelle membranes to impair membrane function. The fruit extract reduced cardiac rate of snails, but the effect seems to be indirect. Ethanolic fruit extracts stimulated oxygen consumption by B. glabrata homogenates, suggesting that extracts uncouple oxidative phosphorylation. These extracts markedly inhibit cholinesterases in the snail mantle. Either purified solasodine alone or synthetized solanine hydrochloride alone did not kill snails.