The detail of the characteristic double whorled branchial crown of the tubiculous polychaete Bispira volutacornis, with its internal skeleton of large vacuolated cells and ciliated radioles, is consistent with the feeding apparatus of sabellids at large. Studies show that ingested particulate matter has at least one dimension less than 15 μm. Feeding seems to be most readily accommodated at current speeds from 1 cm s−1 to 3 cm s−1 with the crown apex angled downstream. Particulate matter passes through the alimentary canal in 7·7 h at 14°C, for an average sized specimen of 97 segments. Whilst the tube provides protection against predatory fish and crustaceans (with ample evidence of sub-lethal cropping of the branchial crown), it also has a role in irrigation and respiration. The worm will retreat within the tube when current flow exceeds 8·7 cm s−1.