Larval Development of Polychaeta from the Northern California Coast V. Ramex Californiensis Hartman (Polychaeta: Terebellidae)

Ramex californiensis is a small intertidal terebellid polychaete that lives in rocky habitats on the northern California coast. The species is abundant under colonies of encrusting tunicates in the low intertidal zone on rocks protected from the surf. The tubes are formed of coarse mucoid secretions covered with sand, shell, and algal fragments. Large elongated, white eggs ranging from 270 to 330 µm (x = 292 µm) are deposited by females in capsules within the tubes. Up to 16 eggs or embryos have been observed in a single capsule. One, two, or three capsules may be found in a single tube. When multiple capsules are present, the embryos contained in separate capsules are always at different stages of development, indicating sequential fertilizations and egg deposition. Pair formation between males and females was not observed. Development is direct and occurs entirely within the capsules. The earliest larval stages are covered with cilia and bear a pair of red, granular eyes. The anterior and posterior ends elongate and the cilia become restricted to an anterior band. The oral structures develop early, with the differentiation of a ciliated vestibule and development of a medial tentacle on the anterior end of the prostomium. The tentacle assists movement within the capsule during their early development. Two additional tentacles appear lateral to the original medial tentacle and develop each a ciliated groove. The latest encapsulated stages have three grooved tentacles, 10–11 segments (eight with capillary notosetae; none with uncini), and a fully developed digestive tract containing remnants of yolk. Upon release from the capsule, an additional pair of tentacles develops and uncini first appear on setiger 3. Juveniles were maintained on cultures of unicellular algae covering the bottoms of the culture dishes. The worms grazed upon these algae by sweeping their tentacles over the bottom where they pick up the cells and transport them to the vestibule. Juveniles secrete thin mucous tubes.