The Resistance of Oncomelania Snail to Molluscicides. I. Sodium Pentachlorophenate.

Snails used: Oncomelania nosophora used in this study was collected from the endemic areas in Yamanashi Prefecture. Only snails which were actively moving when placed in dechlorinated water were selected for the experiment. Chemical used: NaPCP (contains at least 94% of the pure compound) furnished through the courtesy of the Asahi Denka Company was used in this study . This product has been used for the practice or molluscicidal work in Yamanashi Prefecture for several years . Stock solutions were prepared by dissolving 0.1 g of NaPCP in 100 cc of distilled water , and then a series of several twofold dilutions, i. e. 2.0, 1.0, 0.5, 0.25, 0.125, 0.0625 and 0 .03125 ppm, was made. Technic to bring snails in contact with the compound: Ten snails were put into a Petri dish, 12 cm in diameter and 2.5 cm in height, containing 100 cc of the stock solution . The surface of the solution was covered with a vinyl net of fine mesh with a wooden frame to