Metamorphosis and settlement in the Sabellariidae

Settlement and metamorphosis are reviewed in the polychaete family Sabellariidae with emphasis on some ultrastructural features of the premetamorphosed larva of Pbragmatopoma lapidosa, an intertidal reef-building species. A possible sensory structure is described from P. lapidosa larvae which might play a role in substrate selection. Among the factors influencing settlement and metamorphosis in sabellariid larvae are type of substrate, degree of tidal exposure, tolerance of wave energy, phototaxis, presence or absence of gregariousness in settling, and ability of larvae to detect the tube cement of their own species. The larvae of most intertidal reef-building species are induced to settle and metamorphose upon contact with the adult or larval tube cement of their own species.