Syllis lunaris ( Imajima, 1966 ) Imajima, 1966

Martín, Guillermo San, Álvarez-Campos, Patricia & Hutchings, Pat, 2017, The genus Syllis Savigny in Lamarck, 1818 (Annelida: Syllidae: Syllinae) from Australia (second part): four new species and re-description of twelve previously described species, Zootaxa 4237 (2), pp. 201-243 : 216

Syllis lunaris ( Imajima, 1966) , n. comb.

Figure 8

Typosyllis lunaris Imajima, 1966: 282 , fig. 61 a–n; Licher 1999: 246, fig. 104 a–c. Syllis (Typosyllis) lunaris minima Ben-Eliahu, 1977: 26 , figs 9 a–j.

Material examined. AUSTRALIA, WESTERN AUSTRALIA: Kimberley Site 50, East Montalivet Island , 15° 6' S, 125° 18' E, AM W.48536 , 1 specimen, coll. 0 – 6 m, 15 July 1988, by P. Hutchings; Houtman Abrolhos, Beacon Island, Goss Passage, 28° 25' 30" S, 113° 47' E, AM W.48535 , 2 specimens, coll., 19 May 1994.

Description. Longest complete specimen 7 mm long, 0.26 mm wide, with 59 chaetigers. Body slender, dark, with two thin, light transverse lines on each anterior segment, disappearing after proventricular segments. Prostomium almost circular; 4 eyes in trapezoidal arrangement and 2 anterior eyespots. Palps similar in length to prostomium ( Fig. 8 A). Median antenna arising between posterior eyes, with about 22 articles, distinctly longer than combined length of prostomium and palps; lateral antennae shorter than median one, with about 16 articles; median antenna distinctly thicker than lateral ones. Peristomium shorter than subsequent segments, forming a dorsal fold covering the posterior median part of prostomium ( Fig. 8 A). Dorsal tentacular cirri similar in length to median antenna, with about 20 articles; ventral tentacular cirri about half as long as dorsal ones, with 10–12 articles. Dorsal parapodial cirri of anterior segments distinctly longer than body width; dorsal parapodial cirri of chaetigers 1, 3, 4, 6, 9 distinctly longer and thicker, with 35, 37, 34, 31, 31 articles, respectively ( Fig. 8 A); remaining anterior dorsal parapodial cirri shorter and slender, with 18–20 articles; from proventricular segments, dorsal parapodial cirri alternating long cirri thick but not as much as anteriormost ones, with about 20 articles and short cirri, with about 10 articles ( Fig. 8 B). Dorsal cirri dark, with numerous inclusions inside articles. Parapodia distally slightly bilobed. Ventral parapodial cirri digitiform, shorter than parapodial lobes. Compound chaetae with bidentate blades, proximal tooth shorter than distal one, and short spines on margin, being almost smooth on posterior parapodia ( Fig. 8 D, E, F); shafts smooth and gradually thicker from midbody to posterior parapodia ( Fig. 8 E, F). Anterior parapodia with 12–13 compound chaetae each, with blades somewhat elongated, 29–30 µm long above, 12–13 µm long below ( Fig. 8 D); midbody parapodia with 9–11 compound chaetae, with blades 25 µm long above, 17 µm long below ( Fig. 8 E); posterior parapodia with 8–9 compound chaetae each, with blades short and triangular, 21 µm long above, 13 µm long below ( Fig. 8 F). Dorsal simple chaetae on posterior parapodia only, bidentate, with both teeth similar and few short subdistal spines ( Fig. 8 G). Ventral simple chaetae only on far posterior segments, similar to dorsal ones but smooth ( Fig. 8 H). Anterior parapodia with 2–3 aciculae each, distally acute, one more slender than the other ( Fig. 8 I), two aciculae in each midbody parapodium, similar to anterior ones ( Fig. 8 J), and one solitary acicula in each posteriormost parapodium, being large, distally acute with slightly oblique tip ( Fig. 8 K), slightly protruding from parapodial lobes. Pharynx extending through about 10 segments; pharyngeal tooth on anterior margin of pharynx ( Fig. 8 A). Proventricle through 6–7 segments, with about 37 muscle cell rows. Pygidium with 2 anal cirri, with 21–23 articles ( Fig. 8 C).

Remarks. The Australian specimens differ from the original description of Syllis lunaris from Japan in being smaller in size and in having an apparently different colour pattern, dorsally brown with a median oval white spot on anterior segments ( Imajima 1966); however the colouration pattern can disappear or be modified in alcohol after long time term storage; both populations have the characteristic anterior long and thick dorsal cirri alternating with shorter and slender ones, and the compound chaetae and aciculae are also very similar. The reproduction of this species is by means of dicerous stolons (fide Imajima 1966, fig. 61n).

Habitat. Vermetid reefs, dead corals.

Distribution. Japan, Red Sea, Australia (Western Australia).

Figures

FIGURE 8. Syllis lunaris (Imajima, 1966), n. comb. (AM W. 48535). A, anterior end, dorsal view. B, midbody segments, dorsal view. C, pygidium and anal cirri. D, compound chaetae, anterior parapodium. E, compound chaetae, midbody parapodium. F, compound chaetae, posterior parapodium. G, dorsal simple chaeta. H, ventral simple chaeta. I, aciculae, anterior parapodium. J, aciculae, midbody parapodium. K, acicula, posterior parapodium. Scale bars: A – C: 0.4 mm. D – K: 20 µm.