Exogone (Exogone) ingridae n.sp.

Fig. 83A–N

Material examined. AUSTRALIA: NEW SOUTH WALES. HOLOTYPE: AM W26451, 150 m east of Burrill Rocks, 35°23.41'S 150°28.18'E, surface of sponges, 19 m, P. Berents et al., 1 May 1997. PARATYPES: 8 specimens, AM W26452, 150 m east of Burrill Rocks, 35°23.41'S 150°28.18'E, on surface of sponges, 17 m, K.Attwood, 1 May 1997. WESTERN AUSTRALIA. 1 specimen, AM W27090, Goss Passage, Beacon Island, 28°25.5'S 113°47.0'E, dead Acropora plates with sponges, ascidians & algae, 23 m, P.A. Hutchings, 19 May 1994. 1 specimen, AM W27091, off jetty near Fisheries Hut, Beacon Island, 28°25.5'S 113°47.0'E, dead plate-coral substrate, Acropora, Montipora, 12 m, P.A. Hutchings, 23 May 1994.

Description. Body long, relatively broad, 4 mm long, 0.3 mm wide, 38 chaetigers. Prostomium oval to subpentagonal, wider than long; 4 eyes in rectangular arrangement. Antennae ovoid, short, inserted separately between posterior eyes; median antenna about twice as long as lateral antennae, much shorter than prostomium; lateral antennae inserted near posterior eyes (Fig. 83A). Palps broad, longer than prostomium, fused along their length, with a distinct dorsal furrow and a terminal notch (Fig. 83A). Tentacular segment about half as long as following segments; tentacular cirri small, shorter than lateral antennae. Dorsal cirri ovoid, longer than tentacular cirri, similar in length to lateral antennae and parapodial lobes. Parapodia of 3 anterior chaetigers each with solitary compound spiniger-like chaeta, shafts with subdistal long, thin spines, and slender, unidentate blade with short marginal spines (Fig. 83C), 30 µm long, and 4 falcigers, shafts provided with subdistal spines and bidentate blades, subdistal tooth long and broad, distal tooth small and long, thin marginal spines, 2 distalmost of which even longer than whole blade, all blades similar in length, about 9 µm long (Fig. 83D). From chaetiger 4 posteriorly, each parapodium with single compound spiniger-like chaeta, similar to those of anterior parapodia but provided with longer spines, both on shafts and blades (Fig. 83F), in addition with 2 strongly modified falcigers, articulation hemigomph with long spines, and blades curved, provided with long, erect spines connected by a membrane, ending in a long, filiform tip (Fig. 83G), and finally one compound falciger, similar to those of anterior parapodia (Fig. 83H). Posterior parapodia each with one compound spiniger-like chaeta with thick shaft and short, filiform, smooth blade, about 14–15 µm long (Fig. 83J), one strongly modified falciger similar to those of midbody (Fig. 83K), and one falciger with thick shaft and very short, smooth, bidentate blade (Fig. 83L). Dorsal simple chaetae from anterior segments (chaetiger 3 on holotype), with 6 long subdistal spines (aristae), thicker posteriorly (Figs. 83B,E,I). Ventral simple chaetae on posterior parapodia, sigmoid, thick, smooth, bidentate, subdistal tooth longer and thicker than distal tooth (Fig. 83M). Acicula solitary, distally expanded and rounded (Fig. 83N). Pygidium with 2 long anal cirri. Pharynx long, through about 7 segments, everted in holotype, provided with a crown of 10 soft papillae; pharyngeal tooth on anterior rim (Fig. 83A). Proventricle long, similar in length to pharynx, with about 27 muscle cell rows.

Remarks. This species is unique in having strongly modified compound chaetae on mid and posterior parapodia and long aristae on dorsal simple chaetae as well as on the blades of non-modified falcigers.

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

Habitat. On sessile invertebrate substrates such as sponges, bryozoans, dead corals; 12–23 m depth.

Etymology. The species is named in honour of Ms Ingrid Skirka, Sydney, Australia.