Larval development and metamorphosis of Sabellaria cementarium Moore, 1906 (Polychaeta: Sabellariidae)

Abstract

The development of the polychaete Sabellaria cementarium Moore, 1906 proceeds at 10–14 °C, as follows: 23 h, early trochophore with prototroch and apical tuft; 65 h, 1 pair of provisional setae; 3.5 days, feeding trochophore; 18 days, metatrochophore; 4 weeks, metatrochophore with tentacle buds; 5–6 weeks, nectochaeta competent to metamorphose; 6–8 weeks, settlement and metamorphosis. Larval behavior is described. Tube sand of adult sabellariids (S. cementarium, Phragmatopoma lapidosa, ldanthrysus ornamentatus) and beach sand induced metamorphosis. Larvae exhibit a low degree of substrate specificity in their settlement, but sand is essential. Metamorphosis involves a loss of provisional setae, anterior rotation of tentacles and opercular cirri, and reduction of episphere. Following these changes, the juvenile secretes a mucoid tube to which sand grains are attached. Metamorphosis is considered complete when the caudal appendage has formed; this occurs 7–10 days postsettlement. Juveniles were kept in the laboratory for 38 days. During this time, they develop three pairs of tentacles, lose all larval pigment, and form a second thoracic segment. Within the opercular crown, primary opercular paleae replace settling paleae.