The opercular moult in Spirorbis spirorbis (L.) and S. pusilloides Bush (Polychaeta: Serpulidae)

FURTHER OBSERVATIONS ON THE STRUCTURE AND FUNCTION OF THE OPERCULUM INSPIRORBIS MOERCHI(SERPULIDAE: SPIRORBINAE)

“…Light microscopy has revealed the presence of longitudinal muscle fibers embedded within the connective tissue of the opercular peduncle (Potswald, 1968;Thorp and Segrove, 1975); however, the present study has conclusively shown that muscle fibers do not penetrate between the two epithelial layers making up the opercular brood chamber. Since the important study of Cloney (1966) on the contractile role of the caudal epithelium during tail resorption in ascidian larvae, numerous reports have documented the close correlation between contraction and the presence of cytoplasmic microfilaments in a variety of nonmuscle cells (Baker and Schroeder, 1967;Schroeder, 1969Schroeder, , 1970Schroeder, , 1972Schroeder, , 1973Spooner, Yamada, and Wessells, 1971;Wessells, Spooner, Ash, Bradley, Luduena, Taylor, Wrenn, and Yamada, 1971;Conrad, 1973; just to cite a few).…”

“…The bundles of microfilaments observed parallel to the long axes of the columnar cells in the brooding condition, assuming they are also present in the virgin operculum, could possibly play a role in the hypothetical event. Unfortunately, as Thorp and Segrove (1975) point out, neither they nor any other worker have ever observed the actual transfer of oocytes into an opercular brood chamber.…”

“…Thorp and Segrove (1975) have described the oocytes of S. spirorbis as being very fluid during spawning and capable of flowing through an opening with a diameter one-tenth or less that of the oocyte itself.…”

New Spirorbidae (Polychaeta: Sedentaria) from the East Pacific, Atlantic, Indian and Southern Oceans

“…13Hi. This seems to have resulted from a moulting process like that described for Spirorbis spirorbis (Thorp & Segrove, 1975).…”

“…Incubation in an opercular brood chamber which is an invagination from the exterior, so that the embryos are morphologically distal to the cuticle (see Thorp, 1975). The chamber can be used for more than one brood; larval attachment gland single; thoracic uncini with a blunt anterior peg; numbers of abdominal uncini similar on both sides of body; abdominal setae pennant-shaped, usually with a thin (optically transparent) projecting "heel".…”