The association of Glacidorbis occidentalis Bunn and Stoddart 1983 (Gastropoda: Glacidorbidae) with intermittently-flowing, forest streams in south-western Australia

Abstract

The distribution of Glacidorbis occidentalis is considerably more widespread than previously recorded, occurring in streams throughout the northern jarrah forest, Western Australia. The species is largely restricted to forest streams with intermittent flow regimes and does not occur in lowland rivers west of the Darling Range. The association of this species with intermittently-flowing streams is atypical of the genus and cannot be attributed to differences in stream morphology or water chemistry.

G. occidentalis is one of the most common gastropods in the intermittent streams of the northern jarrah forest though it rarely comprises more than a few percent of the total fauna. Adult snails oversummer in the stream bed and emerge shortly after the first winter flows. The species produces brooded young which appear to be released as veligers during the winter months.