Intraspecific Facilitation Research Articles

Intraspecific facilitation of larval recruitment: Gregarious settlement of the polychaete Phragmatopomacalifornica (Fewkes)

The swimming larvae of the polychaete Phragmatopoma californica (Fewkes) (Sabellariidae) are induced to settle, attach to substratum and metamorphose to the juvenile form upon contact with anterior portions of tubes from conspecifics, and are capable of delaying metamorphosis in the absence of such contact. Glass beads with which conspecifics had previously built tubes are potent inducers of metamorphosis; control glass beads previously soaked in sea water (to produce a thin film of organic molecules and microorganisms adsorbed to the surfaces of the beads) are relatively ineffective in inducing metamorphosis. Posterior portions of conspecific tubes, sandstone, a variety of sympatric algal and invertebrate species and tubes from several other polychaete species either do not induce metamorphosis or do so at a lower level than did anterior portions of conspecific tubes. The stimulus for metamorphosis is inactivated by boiling. Recognition of the metamorphosis-inducing stimulus by the larvae is dependent on contact and independent of light. These results suggest that at least some component of the inducing stimulus is chemical in nature. Quinone tanned proteins (or a precursor or enzyme involved in their formation) which form the cementing material secreted by the animal for tube construction may be responsible for the inducing activity of tube material. A discussion of the ecological implications of site-specific recruitment is presented. Gregarious settlement and metamorphosis of P. californica larvae (resulting in an irreversible commitment to the benthos) could contribute to the patchy distribution of the adult population, both by initially forming single-species dominated patches following a disturbance, and subsequently altering the ability of individuals to maintain space when they are aggregated.