Syllis yallingupensis (Hartmann-Schröder, 1982) n. comb.

Figure 23

Typosyllis (Langerhansia) yallingupensis Hartmann-Schröder, 1982: 63, figs 37‒40. Typosyllis yallingupensis Licher 1999: 84, fig. 39.

Material examined. AUSTRALIA, WESTERN AUSTRALIA: Houtman Abrolhos, Beacon Island, Goss Passage, WA 517, 28° 25' 30" S, 113° 47' E, AM W.48573, 1 specimen, coll. 24 m, 21 May 1994 ; Goss Passage, south east end of Long Island, WA 524, 28° 28' 48" S, 113° 46' 30" E, AM W.48574, 3 specimens, coll. 30 m, 22 May 1994 ; Beacon Island, northeast entrance to Goss Passage, WA 536, 28° 27' 54" S, 113° 46' 42" E, AM W.48575, 1 specimen, coll. 33 m, 25 May 1994; Beacon Island, Goss Passage, WA 518, 28° 25' 30" S, 113° 47' E, AM W.48576, 2 specimens, coll. 8 m, 22 May 1994; Goss Passage, north end of Long Island, WA 521, 28° 28' 18" S, 113° 46' 18" E, AM W.48577, 2 specimens, coll. 8 m, 22 May 1994 .

Description. Longest complete examined specimen 13 mm long, 0.41 mm wide, with 119 chaetigers. Body slender, elongated, filiform, without colour pattern. Prostomium rounded; 4 eyes in trapezoidal arrangement and 2 anterior eyespots. Palps elongated, slightly longer than prostomium (Fig. 23 A). Median antenna arising on posterior part of prostomium, between posterior eyes, with about 25 articles, distinctly longer than combined length of prostomium and palps; lateral antennae about half the length of median one, with 17 articles. Peristomium shorter than subsequent segments (Fig. 23 A). Dorsal tentacular cirri slightly shorter than median antenna, with about 23–25 articles; ventral tentacular cirri about 2/3 as long as dorsal ones, with about 16 articles. Dorsal parapodial cirri slender, elongated, whip-shaped, similar or longer than body width, with numerous, dark inclusions in articles (Fig. 23 A, B), anteriormost dorsal parapodial cirri longer than dorsal tentacular cirri. Number of articles in chaetigers 1, 2, 3, 4, and 5, with respectively 30, 14, 28, 30, 14 articles. In midbody, distinctly alternating long cirri, with 28–30 articles, and short cirri, with 18–19 articles (Fig. 23 B). Parapodia conical. Ventral parapodial cirri shorter or similar in length to parapodial lobes. Compound chaetae as heterogomph falcigers, distinctly bidentate, both teeth similar on anterior parapodia, unequal in midbody and posterior parapodia, with proximal tooth distinctly larger than distal one, moderate sized spines on margin, distally curved, and 2–3 distal ones longer, reaching the level of proximal tooth (Fig. 23 D, F, H); compound chaetae also spiniger-like chaetae with moderate spines on margin, unidentate, except those of anterior parapodia, which are slightly bidentate (Fig. 23 C, E, G). Anterior parapodia each with 1–2 spiniger-like, blades distally slightly bidentate, about 50 µm long, moderate, thin spines on margin (Fig. 23 C), and 5–7 falcigers, blades 20 µm long above, 13 µm long below, with both teeth similar, and thin, distally curved spines on margin (Fig. 23 D); midbody parapodia with 1 spiniger-like chaeta each, similar to those of anterior segments but somewhat longer, about 63 µm long, unidentate and with slightly longer spines on margin (Fig. 23 E), and 4–5 falcigers, with thicker shafts than those of anterior parapodia and blades with unequal teeth, proximal tooth somewhat longer than distal one, and thin, distally curved, spines, especially 1–2 distal ones, reaching the level of proximal tooth; blades 18 µm long above, 15 µm long below, (Fig. 23 F); posterior parapodia with 1 spiniger-like chaeta each, similar to those of midbody (Fig. 23 G) (sometimes absent, or with another shorter spiniger-like chaeta present) and 3 falcigers, with thick shafts, and blades similar to those of midbody but with larger proximal tooth, distinctly longer than distal one, 20 µm long above, 15 µm long below (Fig. 23 H). Dorsal simple chaetae from midbody, smooth, relatively thick, distally bifid (Fig. 23 I, J). Ventral simple chaetae on posterior segments only, smooth, sigmoid, strongly bidentate, proximal tooth somewhat larger than distal one (Fig. 23 K). Anterior parapodia with 4 aciculae each (Fig. 23 L), 2 at each midbody parapodium (Fig. 23 M), and single acicula in each posteriormost parapodium, acuminate (Fig. 23 N). Pharynx extending through about 8 segments; pharyngeal tooth on anterior margin of pharynx (Fig. 23 A). Proventricle through 4–5 segments, with about 25 muscle cell rows. Pygidium with 2 short anal cirri, and a median stylus.

Remarks. This species is similar to Syllis cruzi Núñez & San Martín, 1991, but the body in S. yallingupensis is more slender, with longer and more slender dorsal cirri, and it has spiniger-like compound chaetae, which are absent in S. cruzi (see Álvarez-Campos et al., 2015b).

Habitat. Algae, concretions and sediments.

Distribution. Australia (Western Australia).