Opisthosyllis

Linero-Arana, Ildefonso & Diaz Diaz, Oscarn, 2011, Syllidae (Annelida, Polychaeta) from the Caribbean coast of Venezuela, ZooKeys 117, pp. 1-28 : 10

Opisthosyllis sp. Figs 3.1-3.7

Material examined.

IMLR102, (1); IMLR202, (4), as epibionts on Crassostrea rhizophorae , 0-0.5 m.

Description.

Length up to 21 mm, 0.2 mm in width, with 78 chaetigers. Prostomium with two pairs of lentigerous eyes in trapezoidal arrangement on posterior half of prostomium. Antennae longer than prostomium and palps, with 18-19 articles each. Palps separated at the base. Dorsal tentacular cirri with 26 articles, ventral ones with 18. Dorsal cirri, alternating in length longer, with 23-25 articles, and shorter, with 17-19 articles (Fig. 3.1). Compound falcigers unidentate with spiniferous cutting edge, dorsal ones with longer blades (Fig. 3.2) than ventral ones (Fig. 3.3, 3.4). Acicula subterminally thickened (Fig. 3.5, 3.6). Dorsal simple chaeta with slightly bifid tip (Fig. 3.7), only present on last chaetigers. Pharynx extending through 9 chaetigers; with dorsal tooth located at the level of the chaetiger 7; proventriculus extending through 6-7 chaetigers, with about 45 rows of muscle cells.

Remarks.

Opisthosyllis sp. resembles Opisthosyllis brunnea Langerhans 1991, in having compound chaetae with unidentate blades, and in the location of the pharyngeal tooth; it differs in the absence of an occipital flap, having a wider proventriculus, and in the number of rows of muscle cells in the proventriculus.