Syllis heronislandensis Martín & Lucas & Hutchings 2024, n. comb.

Syllis heronislandensis (Hartmann-Schröder, 1991) n. comb.

Figure 4

Typosyllis (Typosyllis) heronislandensis Hartmann-Schröder, 1991: 31, figs 42–46.

Typosyllis heronislandensis.— Licher 1999: 88, fig. 41.

Material examined. AUSTRALIA, WESTERN AUSTRALIA: Kimberley region, St. 59, west side of Cassini Island, 13° 57’ S, 125° 37’ E, coll., P. Hutchings, low tide, 18 July 1988, AM W.54219, 1 specimen.

Additional material examined. Typosyllis (Typosyllis) heronislandensis Hartmann-Schröder, 1991. AUSTRALIA, QUEENSLAND: Heron Island, SW reef, 23º 27’S 151º 55’E, coll. G. Hartmann-Schröder, short, branched beards of algae from corals on the reef edge with some coralline sand and piece of corals, ZMH-P-0020537, Holotype.

Description. Single specimen, complete, 4 mm long, 0.25 mm wide, 62 chaetigers, broken in two pieces after examination. Body small, delicate, without colour markings. Prostomium oval to rounded, with two pairs of small eyes in open trapezoidal arrangement and two anterior, minute eyespots. Palps shorter than prostomium. Median antenna inserted in middle of prostomium, with 15 articles, longer than combined length of prostomium and palps; lateral antennae originating near anterior margin of prostomium, markedly shorter than median antenna, with 12 articles (Fig. 4A). Peristomium shorter than subsequent segments; dorsal tentacular cirri similar in length to median antenna, with 17 articles; ventral cirri with about 10 articles. Dorsal cirri of first chaetiger very long, with 27 articles (Fig. 4A); dorsal cirri of midbody alternating long and short (Fig. 4B); long cirri with about 16 articles, ventral cirri with nine articles; articles globose, spherical, especially on mid-length of cirri, except most distal ones, oval, elongated (Fig. 4A, B). Numerous spiralized glands inside articles of dorsal cirri, less abundant on anterior cirri (Fig. 4A, B). Parapodia bilobed, posterior lobe longer than proximal one (Fig. 4A). Ventral cirri digitiform. Compound chaetae all bidentate falcigers, both teeth of similar size, with long, curved spines on margin on basal part becoming short and straight distally (Fig. 4C–E). Anterior parapodia with 7–9 chaetae, blades 28 µm above, 16 µm below (Fig. 4C); midbody parapodia with five chaetae, blades 20–25 µm above, 12 µm below (Fig. 4D); posterior parapodia with four compound chaetae similar to those of midbody (Fig. 4E). Spines on margin of compound chaetae very thin, sometimes difficult to observe. Dorsal simple chaetae on posterior segments, fine, smooth, distally bidentate (Fig. 4F). Ventral simple chaetae on far posterior segments, similar to dorsal but slightly thicker (Fig. 4G). Anterior parapodia with two thin aciculae, one straight and other slightly curved distally (Fig. 4H); midbody and posterior parapodia each with solitary, acuminate acicula (Fig. 4I, J). Pharynx long and slender, partially everted, through nine segments (Fig. 4A); pharyngeal tooth on anterior margin of pharynx. Proventricle through 6–7 segments, with 36 muscle cell rows.

Remarks. The only examined specimen agrees reasonably well with the Hartmann-Schröder (1991) ’s and Licher (1999) ’s descriptions; the spines on margin of chaetal blades are longer in our specimen and present on all chaetae; however, they are very thin and difficult to see, so they could have been overlooked on the type material. The holotype of the species is a minute, incomplete specimen, which agrees quite well with our specimen. Given the distance between the type locality and this new record from Western Australia, it would be good to confirm this using molecular studies.

Habitat. On algae from coral reefs.

Distribution. Australia. Only known from the type locality (Heron Island) and Kimberley region representing first record from Western Australia.