Exogone (Exogone) haswelli, Guillermo San Martin, 2005

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 : 138-139

Exogone (Exogone) haswelli n.sp.

Fig. 86A–L

Material examined. AUSTRALIA: NEW SOUTH WALES. HOLOTYPE: AM W26443, Palm Beach, Pittwater, 33°35'S 151°19'E, sand, seagrass, Halophila & Posidonia , 3 m, J.K. Lowry & R.T. Springthorpe, 28 Apr 1983. PARATYPES: 20 specimens, AM W26444, Palm Beach, Pittwater, 33°35'S 151°19'E, sand, seagrass, Halophila & Posidonia , 3 m, J.K. Lowry & R.T. Springthorpe, 28 Apr 1983. WESTERN AUSTRALIA. 2 specimens, and 2 specimens on SEM stub, AM W27456, north end of beach, Bundegi Reef, Exmouth Gulf, 21°49'S 114°11'E, rocky rubble, coralline algae with green epiphyte, 2 m, H.E. Stoddart, 4 Jan 1984.

Description. Body long, slender, filiform, 4.6 mm long, 0.3 mm wide, 54 chaetigers. Prostomium oval, wider than long; 4 eyes in trapezoidal to rectangular arrangement. Antennae minute, papilliform, inserted between posterior pair of eyes, close to each other but distinctly separate (Fig. 86A), all similar, difficult to see. Palps broad, long, about twice as long as prostomium, with a dorsal furrow and a distal notch. Peristomium shorter than following segments, laterally and ventrally expanded at anterior end, surrounding prostomium (Fig. 86A); tentacular cirri small, ovoid to papilliform, similar in shape and size to antennae. Two ciliated, distinct nuchal organs. Dorsal cirri ovoid, slightly longer than antennae and tentacular cirri, present on all parapodia (Fig. 86A). Parapodia each with solitary compound chaetae with spiniger-like blade and several falcigers, 3–4 anteriorly to 2 on each posterior parapodia. Spiniger-like chaetae with hemigomph shafts, provided with a distal longitudinal keel with long, thin spines and elongate blades bidentate and short marginal spines (Figs. 86B,E,I), about 28 µm in length on anterior parapodia, 39 µm in midbody, 24 µm on posterior parapodia. Falcigers heterogomph, shafts with a ridge with long, slender spines on anterior and midbody parapodia (Fig. 86C,F), blades with long, thick subdistal tooth and short, small distal tooth, provided with moderate to short marginal spines, 10 µm long on midbody, about 6 µm long on posterior parapodia (Fig. 86J). Dorsal simple chaetae from chaetiger 6 in holotype, distinctly bidentate, with broad teeth and subdistal spines on anterior parapodia (Fig. 86D), progressively thicker, more strongly bidentate with broader teeth, with few short spines (Fig. 86G) or smooth (Fig. 86H). Ventral simple chaetae from midbody, sigmoid, smooth, bidentate, subdistal tooth long and broad, distal tooth much smaller (Fig. 86L). Acicula solitary, distally rounded (Fig. 86K). Pharynx long and slender, through 7 segments; pharyngeal tooth conical, near anterior rim (Fig. 86A). Proventricle long and slender through about 5–6 segments, with 30 muscle cell rows.

Remarks. Exogone (Exogone) haswelli n.sp. is characterized by having minute, papilliform antennae, long proventricle and strongly bidentate dorsal simple chaetae. Similar dorsal simple chaetae are present in Exogone (E.) pseudolourei San Martín, 1991, from the Caribbean Sea, but that species has much longer antennae, especially the median one, much shorter proventricle and enlarged, shafts with a triangular process, on spiniger-like compound chaetae of chaetiger 2 (San Martín, 1991a).

Distribution. Australia (New South Wales, Western Australia).

Habitat. Sand and seagrass, amongst coralline algae, in shallow water.

Etymology. The species is named in honour of the late Professor William Haswell, the first Australian polychaetologist, and one who contributed substantially to our knowledge of the Australian Syllidae .