Syllis cornuta Rathke 1843

Syllis cf. cornuta Rathke, 1843

Fig. 9

Material examined. 1 spec. ZMA V.Pol. 2211.02 (as Syllis sexoculata), Indonesia, 6º8´N 121º19E, 275 m, Siboga Expedition, Sta. 105, 4 July 1899.

Comparative material examined. Syllis cornuta Rathke, 1843. 5 Neotypes (NTNU 410-415). Norway, Trondheimsfjorden, Bergensfjorden (designed by Licher, 1999).

Description. Incomplete specimen, 9 mm long, 0.8 mm wide, with 68 segments. Body strongly pigmented, dark red. Prostomium wider than long, with two pairs of eyes in trapezoidal arrangement, anterior ones larger than posterior. Median antenna inserted on middle of prostomium, broken, with 18 articles. Lateral antennae anteriorly inserted, equal to combined length of prostomium and palps. Palps triangular and broad, longer than prostomium, fused at base, with distinct median groove. Peristomium shorter than subsequent segments (Fig. 9 A). Dorsal tentacular cirri with 23 articles, ventral tentacular cirri shorter, with 15 articles. Anterior dorsal cirri with 15–20 articles not showing clear variation in length, midbody dorsal cirri clearly alternating in length, long ones with 20–25 articles and short ones with 13–15. Ventral cirri conical, proximally inserted, exceeding parapodial lobes in length (Fig. 9 H). Anterior chaetigers with 15 compound heterogomph chaetae. Four dorsal-most blades longer than remaining (ca. 60–75 µm), pseudospiniger, bidentate, with fine spines along blade edge, blades of remaining chaetae dorsoventrally decreasing in length (ca. 40 µm dorsal-most, ca. 25 µm ventral-most) (Fig. 9 C). Midbody parapodia with 18 compound chaetae, two to four pseudospinigers located most dorsally, and remaining falcigers, both similar in length to anterior ones. Posterior chaetigers with 13–18 compound chaetae, dorsal-most pseudospiniger (ca. 75 µm), remaining falcigers shorter than those from anterior chaetigers (ca. 24–40 µm) (Fig. 9 G). Dorsal simple chaetae unidentate, straight, distally with small spines (Fig. 9 E). Sigmoid, bidentate ventral simple chaetae on posterior parapodia (Fig. 9 D). Anterior chaetigers with four straight, pointed aciculae (Fig. 9 B), posterior chaetigers with two, one larger and slightly protruding from parapodia (Fig. 9 F). Pygidium missing. Pharynx long, similar in length to proventricle, with ten distal papillae, quadrangular in shape. Pharyngeal tooth anteriorly located. Proventricle long, extending through 12 segments, number of cell-rows not distinguishable, as insufficient transparency (Fig. 9 A).

Remarks. The specimen agrees with most of the characters of S. cornuta, except for the length of dorsal cirri and segments width, as given by Rathke (1843) and Licher (1999). Dorsal cirri and segments are shorter in the Indonesian specimen; however, the size of our specimen is considerably smaller (9 mm) than the neotype (30 mm). Syllis cornuta was described from Norway and there are many subsequent reports of this species all around the world including Japan and Australia. Licher (1999) revised a large amount of material from different geographical areas, concluding that some reports were dubious. However, our unique specimen does not have any external feature sufficiently distinct to separate it from S. cornuta on morphological grounds.

Distribution. Indonesia. The nominal species occurs in: North Sea, North West Atlantic Ocean, Bering Sea, Pacific Ocean (North West, Japan (?) and Eastern Australia (?)), Mediterranean Sea (?), Red Sea (?), Indian Ocean (South Africa (?)) (? fide Licher, 1999).