THE DEVELOPMENT IN THE LABORATORY OF RESISTANCE TO SODIUM PENTACHLOROPHENATE IN AUSTRALORBIS GLABRATUS.

Although reports-some of them conflicting-have been published on the development of resistance to molluscicides in species of Oncomelania, little or nothing is known of the potential of pulmonate snails to develop such resistance, in particular to the much-used compound, sodium pentachlorophenate. This paper describes efforts made between 1952 and 1961 to developed increased resistance in two laboratory-reared strains of Australorbis glabratus. Two lines were eventually established from 10 successive generations of survivors of a 24-hour exposure to LD(90) dosages of pure sodium pentachlorophenate. Each line showed an increase of 50% in the 24-hour LD(50) dosage of chemical over that of the parent strain (e.g., from 1.09 p.p.m. to 1.70 p.p.m. for one strain). While this increase seems low in comparison with dosages recommended for application in the field, it does indicate that colonies of A. glabratus with an increased level of resistance to NaPCP can be developed.