Feeding and the epiphyte food resources of gastropods living on leaves of the SeagrassAmphibolis griffithii in south-western Australia

Abstract

This paper reports the radula structure and diets of trochid ( Thalotia conica, Prothalotia lehmanni) and columbellid (Pyrene bidentata) gastropods that reside amongst the terminal leaf clusters of the seagrass, Amphibolis griffithii, in shallow, subtidal regions of south-western Australia. Both trochids possessed similar rhipidoglossan radulae that swept diatoms, small encrusting coralline algae and other organisms from the seagrass leaves. Pyrene bidentata used similar food resources but also consumed some larger food fragments (e.g. hydroid colonies) with its rachiglossan radula.

Snail diets most closely reflected the range and abundance of epiphytes on leaves in summer. During particularly the winter, certain diatoms were disproportionately present in snail diets, either through active food selection or because some diatoms were patchily distributed on leaves. Although unidentifiable materials accounted for about 20–35% by volume of food present in snail stomachs, our data support the view that epiphytes can be more important than detritus in sustaining the food webs of vagile gastropods in seagrass ecosystems.