Exogone (Parexogone) gambiae Lanera, Sordino & San Martín, 1994

Exogone (Parexogone) gambiae Lanera, Sordino & San Martín, 1994 View in CoL

Fig. 71A–H

Exogone (Parexogone) gambiae Lanera et al., 1994: 236 , figs. 2, 3; San Martín, 2003.

Material examined. AUSTRALIA: QUEENSLAND. 1 specimen, AM W26549, Halifax Bay, north of Townsville, 19°10'S 146°38'E, 5 m, Queensland Nickel Pty Ltd, Jan 1977. 1 specimen, AM W26550, Halifax Bay, north of Townsville, 19°9'S 146°37'E, 5 m, Queensland Nickel Pty Ltd, July 1977. 4 specimens, AM W26551, Halifax Bay, north of Townsville, 19°10'S 146°44'E, 5 m, Queensland Nickel Pty Ltd, July 1977. 2 specimens, AM W26554, Halifax Bay, north of Townsville, 19°10'S 146°38'E, 5 m, Queensland Nickel Pty Ltd, July 1977. 1 specimen, AM W26563, Halifax Bay, north of Townsville, 19°10'S 146°38'E, 5 m, Queensland Nickel Pty Ltd, July 1977. NEW SOUTH WALES. 1 specimen, AM W26435, 100 m north west of Split Solitary Island, 30°14.0'S 153°10.8'E, mixed red algae, 15 m, S.J. Keable, 7 Mar 1992. SOUTH AUSTRALIA. 1 specimen, AM W26755, Elliston Reef, 33°39'S 134°53'E, algae from reef flat at low tide, P.A. Hutchings, 11 Mar 1979. WESTERN AUSTRALIA. 1 specimen, AM W26513, Goss Passage, Beacon Island, 28°25.5'S 113°47.0'E, dead plates of Acropora , covered in coralline algae, 20 m, P.A. Hutchings, 20 May 1994. 1 specimen, AM W27046, 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 W27047, 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. 1 specimen, AM W27048, north end of Long Island, 28°27.9'S 113°46.3'E, dead coral substrate covered in coralline & brown algae, 6 m, C. Bryce, 22 May 1994. 2 specimens,AM W27049, 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 W27050, Goss Passage, Beacon Island, 28°25.5'S 113°47.0'E, dead coral substrate embedded in fine sediment, 33 m, P.A. Hutchings, 23 May 1994. 1 specimen, AM W27051, off south end of Long Island, Beacon Island, 28°28.8'S 113°46.3'E, dead coral substrate covered in coralline algae, 5 m, P.A. Hutchings, 25 May 1994. 2 specimens, AM W27052, southwest corner of Lucas Island, 15°13'S 124°31'E, 30 m, P.A. Hutchings, 24 July 1988.

Description. Body small, about 1.8 mm long, 0.12 mm wide, 27 chaetigers. Prostomium oval; 4 small eyes in trapezoidal arrangement, and 2 small anterior eyespots; antennae inserted close to each other, on middle of prostomium (Fig. 71A); median antenna long, cylindrical, slightly longer than prostomium and palps together; lateral antennae shorter than prostomium, median antenna about 5 times as long as lateral antennae. Palps broad, completely fused along their length, longer than prostomium, forming a triangular piece (Fig. 71A). Peristomium similar in length to following segments; tentacular cirri papilliform, shorter than lateral antennae. Dorsal cirri papilliform, shorter than parapodial lobes, larger than tentacular cirri but shorter than lateral antennae, absent on chaetiger 2 (Fig. 71A). Anterior parapodia each with 2–3 compound chaetae with spinigerlike blades, indistinctly bidentate, distal tooth rounded and subdistal tooth small, marginal spines moderate and coarse (Fig. 71C), about 25 µm long, in addition 8 compound falcigers, with short blades, slight dorsoventral gradation, 12 µm above, 6 µm below, distinctly bidentate (Fig. 71D) and short marginal spines. Number of spiniger-like chaetae on each parapodium progressively decreasing posteriorly, absent from midbody; middle and posterior parapodia with compound heterogomph falcigers, 5 on posterior parapodia, distinctly bidentate, provided with short, fine marginal spines (Fig. 71G); blades of posterior parapodia about 13 µm above, 9 µm below. Dorsal simple chaetae from anterior parapodia, usually from chaetiger 1, distinctly bidentate, with short marginal spines (Fig. 71B), increasingly thicker posteriorly (Fig. 71F). Ventral simple chaetae on posterior parapodia, sigmoid, smooth, distinctly bidentate (Fig. 71H). Solitary acicula, distally rounded (Fig. 71E). Pygidium bilobed, with 2 long anal cirri. Pharynx long, through about 5–6 segments, pharyngeal tooth near anterior rim (Fig. 71A). Proventricle though 3–4 segments, with about 15 muscle cell rows.

Remarks. Exogone (P.) acutipalpa Kudenov & Harris, 1995 is similar, but it has unidentate dorsal simple chaetae, the long-bladed compound chaetae with proportionally longer blades, and the blades diminishing progressively in length on the parapodia (Kudenov & Harris, 1995).

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

Habitat. Seagrass, algae, dead coral, sand, intertidal to about 30 m depth.