Chemoautotrophy in Bivalve Molluscs of the Genus Thyasira

Abstract

The bivalves Thyasiraflexuosa and T. sarsi have enlarged gills which contain numerous prokaryotes. Gills from freshly collected animals contain high concentrations of elemental sulphur. Homogenates of gill tissue show activity for ribulosebisphosphate carboxylase, adenylylsulphate reductase, sulphate adenylyltransferase and sulphate adenylyltransferase (ADP), indicating that the prokaryotes are sulphur-oxidizing autotrophs. Both species can burrow to depths of 8 cm below the sediment surface and use their vermiform feet to construct channels penetrating deeper into the sediment. T.flexuosa and T. sarsi are scarce in sediments with high hydrogen sulphide concentrations and are not found in sediments where the sulphide zone is below their burrowing depth.