Syllis rosea Langerhans 1879

Syllis rosea (Langerhans, 1879)

Figure 20

Ehlersia (Syllis) rosea Langerhans, 1879: 538, fig. 5.

Ehlersia rosea. Langerhans 1881: 98.

Langerhansia rosea. Imajima 1966: 259, text-fig. 52 a–m; Campoy 1982: 395, pls. 41–43. Langerhansia rosea curticirris Ben-Eliahu, 1977: 44, figs 18 a–h. Typosyllis rosea. Licher 1999: 44, fig. 21a–o.

Syllis rosea. San Martín 2003: 358, fig. 194A–I.

Material examined. AUSTRALIA, WESTERN AUSTRALIA: Kimberley, west side of Cassini Island, St. 59, 13° 57' S, 125° 37' E, AM W.48558, 1 specimen, 18 July 1988, coll. P. Hutchings; south side of North Slate Island, St. 5, 15° 32' S, 124° 24' E, AM W.48559, 2 specimens, coll. 9 July 1988, by P. Hutchings; Condillac Island, St. 54, 14° 6' S, 125° 33' E, AM W.48563, 5 specimens, coll. 16 July 1988 by P. Hutchings; Houtman Abrolhos, Beacon Island, Goss Passage, WA 511, 28° 25' 30" S, 113° 47' E, AM W.48560, 1 specimen, 10 m, coll. 18 May 1994; off south end of Long Island, Beacon Island, WA 539, 28° 28' 48" S, 113° 46' 18" E, AM W.48561, 18 specimens, coll. 4–5 m, May 1994; south end of Long Island, Beacon Island, WA 524, 28° 28' 48" S, 113° 46' 30" E, AM W.48562, 5 specimens, coll. 30 m, 22 May 1994; Goss Passage, Beacon Island, WA 511, 28° 28' 48" S, 113° 46' 30" E, AM W.48560, 1 specimen, coll. 10 m, 22 May 1994; Beacon Island, Goss Passage, WA 518, 28° 25' 30"S, 113° 47' E, AM W.48564, 9 specimens, coll. 8 m, 22 May 1994; Warnbro Sound, West of Penguin Island, 32° 20’S, 115° 43’E, AM W.29518, 1 specimen, coll. from reef substrate, algal sponge, 5 m, 21 March 1993 by P. Hutchings. NORTHERN TERRITORY: Darwin Harbour, off Nightcliff, Old Man's Rock, NT 318, AM W.48565, 2 specimens, coll. 17 July 1993.

Description. Longest complete specimen examined 15 mm long, 0.175 mm wide, with 117 chaetigers. Body long and slender, filiform, without colour pattern; segments well marked, with deep intersegmental constrictions in midbody segments. Prostomium rounded; 4 eyes in open trapezoidal arrangement. Palps elongated, longer than prostomium (Fig. 20 A). Median antenna arising on middle of prostomium, with 18 articles, distinctly longer than combined length of prostomium and palps; lateral antennae about half of length of median one, with 12–13 articles. Peristomium distinctly shorter than subsequent segments (Fig. 20 A). Dorsal tentacular cirri shorter than median antenna, with about 14–15 articles; ventral tentacular cirri, with 10–11 articles. Dorsal parapodial cirri of chaetiger 1 long, with 20–21 articles, distinctly longer than body width (Fig. 20 A), subsequent dorsal parapodial cirri shorter than body width, with few articles, alternating in length, 13–10 articles on anterior segments (Fig. 20 A), 9–10 articles in midbody, with articles of different sizes (Fig. 20 B); dorsal parapodial cirri relatively thick, with numerous and distinctly coiled hyaline inclusions on articles (Fig. 20 B). Ventral parapodial cirri digitiform, shorter than parapodial lobes. Compound chaetae of anteriormost and posterior parapodia elongated, bidentate falcigers; after few anterior parapodia, blades of dorsalmost compound chaetae distinctly elongated, short spiniger-like, about 62 µm long throughout, anteriorly bidentate (Fig. 20 C), becoming indistinctly bidentate to unidentate in midbody, with tip broad and rounded, (Fig. 20 F). Each anteriormost parapodium with 10 falcigers; anterior and midbody parapodia each with 1 spiniger-like and 4 falcigers, bidentate, with short to moderate spines on margin, 16 µm long above, 9 µm long below (Fig. 20 D); far posterior parapodia each with 1 spiniger-like chaeta and 2–4 falcigers, similar to those of midbody (Fig. 20 G); posteriormost parapodia with 4–5 falcigers. Dorsal simple chaetae on posterior parapodia only, truncate, slightly bifid, with few, short subdistal spines (Fig. 20 H). Ventral simple chaetae on far posterior segments only, bidentate, with short spines on margin (Fig. 20 I). Aciculae distally bent at right angle (Fig. 20 E, J), usually solitary, two aciculae in anterior parapodia of longer specimens. Pharynx extending through about 10 segments; pharyngeal tooth on anterior margin of pharynx (Fig. 20 A). Proventricle through 4–5 segments, with about 28–30 muscle cell rows. Pygidium with 2 anal cirri, with 10–11 articles, and median stylus.

Remarks. The specimens from Australia agree well with the descriptions of S. rosea from other areas of the world, except in the tip of midbody spiniger-like chaetae of some specimens, which are markedly less rounded and broad than in specimens from other areas. However, the general characters of body, aciculae and chaetae agree perfectly with the accepted diagnosis of the species, so the difference observed is not considered to be important enough to describe a new species.

Syllis rosea is very similar to S. erikae described above; both species have long and slender body, truncate dorsal simple chaeta, and posterior “foot-like” aciculae, as well as the same kind of stolon (Tetracerous) (not observed in Australian specimens but described from Mediterranean material, San Martín 2003); however, S. rosea has spiniger-like chaetae, which are lacking in S. erikae.

Habitat. Biogenic concretions (calcareous algae, vermetid reefs, dead corals) algae, rhizomes of seaweeds, coarse sand, among mussels, corals and inside sponges (San Martín, 2003).

Distribution. Eastern Atlantic, from NW of Iberina Peninsula to Canary Islands. Warm areas of the Mediterranean Sea, Red Sea, Pacific Ocean (Japan, Solomon Islands). Australia (Western Australia and Northern Territory). This is a new record for Australia.