Exogone (Parexogone) homosetosa Hartmann-Schröder, 1965

Guillermo San Martin, 2005, Exogoninae (Polychaeta: Syllidae) from Australia With the Description of a New Genus and Twenty-two New Species, Records of the Australian Museum 57, pp. 39-152 : 121-122

Exogone (Parexogone) homosetosa Hartmann-Schröder, 1965

Fig. 73A–E

Exogone homosetosa Hartmann-Schröder, 1965b: 295, figs. 296, 297.

Material examined. AUSTRALIA: QUEENSLAND. 1 specimen, AM W26889, Hinchinbrook Channel, 18°20'S 146°4'E, tidal mud- and sandflats, S. Dittmann, 20 Nov 1988. 1 specimen, AM W26930, Missionary Bay, Hinchinbrook Island, 18°13'S 146°14'E, mangroves & adjacent mudflat, epifauna on buoy, S. Dittmann, 3 May 1989. NEW SOUTH WALES. 2 specimens, AM W26453, Split Solitary Island, 30°15'S 153°11'E, 17 m. 1 specimen, AM W26454, North Ledge, Cook Island, 28°11.44'S 153°34.67'E, sponge, 10 m, A.R. Parker, 08 Jun 1993. WESTERN AUSTRALIA. 1 specimen, AM W27085, Goss Passage, Beacon Island, 28°25.5'S 113°47.0'E, dead Acropora plates with sponges, ascidians & algae, 32 m, P.A. Hutchings, 19 May 1994. 1 specimen, AM W27086, Goss Passage, Beacon Island, 28°25.5'S 113°47.0'E, dead Acropora plates covered in coralline algae, 8 m, P.A. Hutchings, 19 May 1994. 1 specimen, AM W27087, Goss Passage, Beacon Island, 28°25.5'S 113°47.0'E, dead coral plates covered in coralline algae, 8 m, P.A. Hutchings, 22 May 1994. 2 specimens, AM W27088, southeast end of Long Island, 28°28.8'S 113°46.5'E, dead coral embedded in calcareous substrate, 30 m, P.A. Hutchings, 22 May 1994. 1 specimen,AM W27089, northeast entrance to Goss Passage, Beacon Island, 28°27.9'S 113°46.7'E, dead branching Acropora with coralline & brown algae, 24 m, P.A. Hutchings, 25 May 1994.

Description. Body slightly elongate, but proportionally shorter than other species, 3.5 mm long, 0.16 mm wide, 40 chaetigers. Prostomium ovate, wider than long; 4 eyes in rectangular arrangement, small in inmature specimens, large and close to each other on each side in mature ones (Fig. 73A), and 2 anterior eyespots. Antennae inserted close to each other, just in front of anterior eyes or between them; median antenna elongate, cylindrical, shorter than combined length of half of prostomium and palps; lateral antennae about 1 ⁄ 3 of length of median antenna, ovate (Fig. 73A). Palps long, triangular, completely fused along their length, with a slight dorsal furrow (Fig. 73A). Peristomium slightly shorter than following segments, covering dorsally posterior part of prostomium; tentacular cirri small, papilliform, smaller than lateral antennae. Dorsal cirri papilliform, smaller than lateral antennae but larger than tentacular cirri, absent on chaetiger 2, shorter than parapodial lobes (Fig. 73A). Compound chaetae heterogomph, shafts with small subdistal spines, similar throughout, blades bidentate, with small subdistal tooth and moderate, coarse marginal spines, 1–2 with longer blades (20 µm) and remaining shorter, (13– 10 µm) (Fig. 73B); anterior parapodia each with about 12 compound chaetae, numbers diminishing progressively posteriorly to 5 on posterior parapodia. Dorsal simple chaetae from post-proventricular segments, nearly smooth, distally blunt, slightly bidentate (Fig. 73C). Ventral simple chaetae on posterior parapodia, sigmoid, with a few, short subdistal spines, distinctly bidentate (Fig. 73D). Acicula solitary, distally expanded and rounded (Fig. 73E). Pharynx through about 5 segments; pharyngeal tooth on anterior rim (Fig. 73A). Proventricle similar in length to pharynx, through about 4–5 segments, with 25 muscle cell rows. Pygidium small, with 2 anal cirri similar in length and shape to median antenna.

Distribution. Chile. Australia (NSW, Western Australia).

Habitat. In dead corals with other organisms; up to 32 m depth.