Observations on the habitat and biology of a lymnaeid snail, Austropeplea vinosa (Gastropoda : Pulmonata), an intermediate host for avian schistosomes in tropical Austarlia

Abstract

The aquatic snail A. vinosa is widely distributed in northern Queensland, occurring in rivers and in static waters, both semipermanent and permanent. The snail is capable of breeding throughout the year. although fewer small snails are present during the cooler months. Rainfall rather than temperature appears to be the main factor influencing populations of A. vinosa, very small snails being able to survive drought by aestivating in the mud. Heavy summer rains refill temporary habitats, and small snails emerge to recommence growth. The same summer rains flood permanent habitats and can wash away snail populations living there. Infection levels of larval flukes in A. vinosa are generally lowest in the wet season and rise as the dry season progresses. The effects of wet season floods and steadily diminishing water levels during the dry season are thought to account for this. The risk of human bathers contracting schistosome dermatitis is therefore highest in the early summer, towards the end of the dry season, when the larvae of avian schistomes are most abundant.