Syllis ypsiloides Aguado, San Martín & ten Hove, 2008

Martín, Guillermo San, Lucas, Yolanda & Hutchings, Pat, 2024, The genus Syllis Savigny in Lamarck, 1818 (Annelida: Syllidae: Syllinae) from Australia (Fourth part), Zootaxa 5453 (1), pp. 1-32 : 18

Syllis ypsiloides Aguado, San Martín & ten Hove, 2008

Figure 12

Syllis ypsiloides Aguado, San Martín & ten Hove, 2008: 36 , figs 16–18.

Material examined. AUSTRALIA, QUEENSLAND: Torres Strait, Prince of Wales Island, bommies northwest of Bamfield Point , 10° 41’ 7” S, 142° 6’ 1” E, coll. 3 Oct 2006, by SCUBA, 3 m, from rocks, AM W.54246, 3 specimens ; Keppel Island , 23° 09’ S, 151° 00 E, 51 m, coll. T. Nielson, 1 Aug 1970, AM W.4382, 1 specimen . NEW SOUTH WALES: Sydney Harbour, White Bay Berth 3, 33° 51’ 47” S, 151° 11’ 00” E, coll. M. Capa, K. B. Attwood, R. T. Springthorpe & G. Fonseca, 5 Mar 2009, from wharf piles, 11.8 m, G. San Martin id., AM W.54887, 2 specimens .

Description. Body long and slender, longest specimen (incomplete) 18 mm long, 0.8 mm wide, 96 chaetigers, without colour markings or single, faint transverse reddish band on anterior segments ( Fig. 12A ) on large specimens. Prostomium rounded, with two pairs of small eyes in open trapezoidal arrangement apparently without eyespots. Median antenna inserted on middle of prostomium, longer than combined length of prostomium and palps, with 19 articles; lateral antennae inserted in front of anterior eyes, shorter than median antenna, with 12₋₋15 articles. Palps similar in length to prostomium ( Fig. 12A ). Peristomium shorter than subsequent segments; dorsal tentacular cirri slightly shorter than median antenna, with 23 articles; ventral tentacular cirri distinctly shorter than dorsal ones, with about 12 articles. Dorsal cirri of first chaetiger long, with 28₋₋29 articles. Anterior dorsal cirri elongated, alternating long and short cirri, long ones similar in length to body, with about 17₋₋20 articles, shorter ones with about 12 articles; chaetigers from end of pharynx dorsal cirri shorter, all similar, alternating long ones with 14 articles and short ones, with 12 articles ( Fig. 12A ). On midbody, dorsal cirri short, fusiform, alternating with some elongated ones, with 11 articles, and thick ones, with eight articles ( Fig. 12B ); on posterior chaetigers dorsal cirri spindle-shaped, shorter and thicker, with about eight articles ( Fig. 12C ). Anterior parapodia with about 10 compound chaetae each; blades elongated, distally acute, bidentate with small proximal tooth and short spines on margin; blades with marked dorso-ventral gradation, 43 µm above, 20 µm below ( Fig. 12D ); posteriorly, number of chaetae reduced to only two, one ypsiloid, large and other much smaller, with thick shaft and small, short, smooth blade, not fused to shaft ( Fig. 12E ). Anterior parapodia with three thin, acuminate aciculae ( Fig. 12F ); from midbody onwards two thicker aciculae ( Fig. 12G ). Pharynx long, through 17 segments; pharyngeal tooth conical, on anterior margin of pharynx. Proventricle long, through nine segments, with about 45 muscle cell rows.

Remarks. Syllis ypsiloides is very similar to S. picta ( Kinberg, 1866) redescribed in a previous paper ( Álvarez-Campos et al., 2015a); they differ mainly in the number of non- fused, compound chaetae in midbody parapodia, with two in S. picta and only one in S. ypsiloides .

Habitat. Sandy and muddy bottoms with dead corals and sponges, sublittoral to 55 m.

Distribution. Indonesia and Australia (QLD, NSW).

Figures

FIGURE 12. Syllis ypsiloides Aguado, San Martín & ten Hove, 2008. A, anterior end, dorsal view. B, long and short dorsal cirri, middle segments. C, long and short dorsal cirri, middle posterior segments. D, compound chaetae, anterior parapodium. E, chaetae, midbody parapodium. F, aciculae, anterior parapodium. G, aciculae, midbody parapodium. AM W.4302. Scale. A-C: 0.4 mm. D-G: 20 µm.