Syllis ergeni Çinar, 2005

Figures 1, 2

Syllis ergeni Çinar, 2005: 45, figs 2–4.

Material examined. AUSTRALIA, WESTERN AUSTRALIA: Rottnest Island, Longreach Bay, 32° S, 115° 30’ E, 25 Jun 2008, on algae, 1 m, coll. M. T. Aguado & G. San Martín, AM W.33398, 1 specimen ; Houtman Abrolhos Islands, east side of Rat Island, 28° 44’ S, 113° 47’ E, 21 June 2008, on algae associated with Posidonia, 1 m, coll. M. T. Aguado & G. San Martín, AM W.33386, 1 specimen .

Description. Both complete specimens; longest specimen 5 mm long, 0.48 mm wide, 65 chaetigers. Body large anteriorly, markedly convex, becoming tapered from midbody, uniformly brown dark dorsally on most anterior segments, becoming lighter from midbody, with a transverse brown band on anterior margin of each segment and few, scattered lines on other part, and without any colour on posterior segments (Fig. 1A, C). Under high magnifications, dorsum with three kinds of spots, most numerous ones dark brown, others light brown and some rounded areas without any colour. Body and appendages strongly contracted by fixation. Prostomium oval, with two large pairs of eyes in open trapezoidal arrangement, and some brown patches. Antennae thick, coiled, difficult to count articles; median antenna inserted on posterior part of prostomium, with about 19 articles; lateral antennae inserted on anterior margin, in front of anterior eyes, with about 17 articles. Palps large, ventrally folded (Fig. 1B). Peristomium shorter than subsequent segments. Dorsal tentacular cirri coiled, with about 24 articles; ventral tentacular cirri shorter, with about 14 articles. Dorsal cirri thick, shorter than body width, with about 23 articles in long and 12 in short ones; antennae, tentacular and dorsal cirri pale, markedly lighter than dorsum (Fig. 1A–C). Parapodia conical, broad, ending in small dorsal and ventral papillae. Compound chaetae heterogomph, bidentate falcigers, with proximal teeth acute, smaller than distal teeth and moderate, straight spines on margin (Fig. 2A–C). Anterior parapodia with 11–12 chaetae, all similar, blades 26 µm above, 20 µm below (Fig. 2A); midbody parapodia with 9–10 chaetae, blades 22 µm above, 19 µm below (Fig. 2B); posterior parapodia with 5–7 compound chaetae, all blades similar, strongly bidentate, 20–16 µm long (Fig. 2C). Dorsal simple chaetae on posterior parapodia, distally bifid, apparently smooth (Fig. 2D). Ventral simple chaetae on most posterior parapodia, apparently smooth, distally bidentate with proximal tooth smaller than distal one (Fig. 2E). Anterior parapodia with 3–4 slender aciculae, distally blunt (Fig. 2F), number of aciculae reducing to two in midbody parapodia one acuminate and one blunt (Fig. 2G) and single on posterior parapodia, distally slightly oblique (Fig. 2G). Pygidium with two long anal cirri. Pharynx and proventricle not seen in dorsal view; in ventral view, proventricle between segments 10 to 18, with about 25 muscle cell rows.

Remarks. These two specimens agree quite well with the original description of Syllis ergeni made by Çinar (2005), based on specimens from the Eastern Mediterranean. However, the pigmentation is slightly different; in the Mediterranean specimens it is dark brownish in the anterior segments, becoming pale progressively posteriorly, but in the Australian specimens the anterior segments have three kinds of spots (dark brown, pale brown and rounded unpigmented areas), and the median segments have one anterior line and only scattered patches of colour. Furthermore, the Mediterranean specimens have numerous spherical glands on anterior segments and bacillary glands on posterior segments, which are lacking on the Australian specimens.

The original description was based on specimens collected from Izmir Bay, Turkey a harbour with contaminated sediments. Çinar (2005) hypothesized that it is probably an introduced species from the Indo-Pacific. Certainly, some specimens examined from Kuwait are identical with this Australian material (unpublished data).As it was also found in the Red Sea and predominantly occurs in the Levant Sea, it was considered as an alien species introduced to the Mediterranean via the Suez Canal (Lessepsian migrant) (Çinar et al., 2017, 2021)