Exogone (Parexogone) annamurrayae

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 : 114-115

Exogone (Parexogone) annamurrayae n.sp.

Fig. 66A–I

Material examined. AUSTRALIA: VICTORIA. HOLOTYPE and 8 PARATYPES, MV F62487, Eastern Bass Strait, 18.1 km W of Pt. Ricardo, 37°49.30'S 148°25.44'E, sand and shell, 27 m, 28 Sep 1990. PARATYPE: 1 specimen, MV F62734, Eastern Bass Strait, Victoria, 5 km W of Cape Conran, 37°48.85'S 148°39.85'E, coarse sand, 22 m, Feb 1991.

Description. Body long, slender, filiform, holotype is a complete specimen, broken in two pieces, 5 mm long, 0.16 mm wide, 60 chaetigers. Prostomium ovate, wider than long; 4 small eyes nearly in square arrangement and 2 minute anterior eyespots (Fig. 66A), but most of the examined specimens apparently without eyes, which disappear after fixation (Fig. 66B). Antennae inserted approximately on middle along of prostomium; median antenna long, approximately twice as long as combined length of prostomium and palps, lateral antennae similar in length to combined length of prostomium and palps (Fig. 66B) or slightly shorter (Fig. 66A). Palps completely fused to each other, similar in length to prostomium or longer. Peristomium similar in length to following segments, covering posterior margin of prostomium; tentacular cirri small, papilliform (Fig. 66A,B). Dorsal cirri on all segments, oval, elongate, shorter than parapodial lobes (Fig. 66A,B). Anterior parapodia each with about 5–6 compound chaetae, with hemigomph articulation, smooth shafts, and short, bidentate blades with both teeth similar or subdistal tooth slightly smaller than distal tooth, short marginal spines (Fig. 66D), showing slight dorsoventral gradation in length, 14 µm above, 9.6 µm below. Number of compound chaetae on each parapodium decreasing posteriorly to 3 on each posterior parapodia, one of these with slight elongate blade, bidentate with both teeth similar and short marginal spines (Fig. 66F), about 17 µm long, and other two compound chaetae with short blades, strongly bidentate, and moderately long marginal spines (Fig. 66I), about 10–11 µm long; posteriormost parapodia with all chaetae similar to those described above (Fig. 66G), usually one with thick shaft and broad subdistal tooth, forming wide angle with distal tooth (Fig. 66J). Dorsal simple chaetae from about chaetiger 6; anterior dorsal simple chaetae slender, indistinctly bidentate, marginally smooth, provided with 4 long subdistal spines, extending beyond tip (Fig. 66C); progressively, dorsal simple chaetae thicker, broader, more strongly bidentate, with subdistal tooth slightly longer than distal one (Fig. 66E). Ventral simple chaetae from chaetiger 44 in holotype, thick, bidentate, distal tooth distally directed with subdistal tooth nearly right angles, triangular, longer and broader than distal tooth; provided with 4 long spines (aristae), some of them surpassing tip (Fig. 66H). Acicula solitary, distally slightly expanded and rounded. Pharynx long, through about 5 segments; pharyngeal tooth conical, long (Fig. 66A,B), on anterior rim. Proventricle shorter than pharynx, through about 2–3 segments, with 20–22 muscle cell rows. Pygidium small, slightly bilobed, with two long anal cirri.

Remarks. San Martín (1991a) provided a key for identification of species of Exogone (Parexogone); E. (P.) annamurrayae n.sp. is the only species with aristae both on dorsal and ventral simple chaetae and lacking spiniger-like chaetae.

Distribution. Australia (Victoria).

Habitat. On coarse sand, in moderate depths (c. 20–30 m).

Etymology. The species is named in honour of Miss Anna Murray, of The Australian Museum.