Exogone (Parexogone) wilsoni, 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 : 115-116

Exogone (Parexogone) wilsoni n.sp.

Fig. 67A–G

Material examined. AUSTRALIA: VICTORIA. HOLOTYPE and 28 PARATYPES, MV F62118, Eastern Bass Strait, 5.7 km W of Cape Conran, 37°48.85'S 148°39.85'E, coarse sand, 22 m, 4 Jun 1991. PARATYPE: 1 specimen, MV F62734, Eastern Bass Strait, 5.7 km of Cape Conran, 37°48.85'S 148°39.80'E, 22 m depth, Feb 1991. PARATYPES: 2 specimens, MV F87423, Southern Port Phillip Bay, 144°55'E 38°21'S, sand, 4 m, 12 Oct 1971. NEW SOUTH WALES. 1 specimen, AM W21623, 1500 m offshore, east of Ramsgate Baths, Botany Bay, 33°59.16'S 151°09.96'E, 5 m, Australian Museum party, 7 Apr 1992. 1 specimen, AM W21624, 500 m west of north Port Botany, east Botany Bay, 33°58.28'S 151°11.98'E, 7 m, Australian Museum party, 28 July 1992. 1 specimen, AM W22621, Cararma Inlet, Jervis Bay, 35°0'S 150°46.5'E, Zostera capricorni, L. Howitt, Mar 1989 . 1 specimen, AM W23580, Foreshore Beach, Botany Bay, 33°57.4'S 151°11.4'E, sand, Kinhill Engineers, Jan 1992. 1 specimen, AM W23913, Port Hacking, 34°04.11'S 151°06.37'E, sand, 13.4 m, Australian Museum Party, 31 May 1994. 1 specimen, AM W23914, Port Hacking, 34°04.00'S 151°06.38'E, sand, 16.9 m,Australian Museum Party, 10 Aug 1995. 1 specimen, AM W26515, south of airport runway extension, northeast Botany Bay, 33°58.13'S 151°11.16'E, 5 m, Australian Museum party, 6 Apr 1992, NSW 767. 1 specimen, AM W26516, south of airport runway extension, northeast Botany Bay, 33°58.13'S 151°11.16'E, 5 m, Australian Museum party, 6 Apr 1992. 1 specimen, AM W26517, 800–1000 m off Port Botany, east side of Botany Bay, 33°58.75'S 151°11.03'E, 7 m,Australian Museum party, 6 Apr 1992. 1 specimen, AM W26518, 800 m WSW from tip of airport runway extension, Botany Bay, 33°58.33'S 151°10.22'E, 7 m, Australian Museum party, 27 July 1992.

Description. Body small and slender, moderately long, 2.8 mm long, 0.2 mm wide, 40 chaetigers. Prostomium oval, wider than long; 4 small eyes in trapezoidal arrangement and 2 minute anterior eyespots (Fig. 67A,B); antennae inserted close to each other, just in front of anterior eyes, lateral antenna cylindrical, long, similar in length to combined length of prostomium and palps, lateral antennae about ¼ length of median antenna. Palps broad, completely fused to each other, forming a triangular piece, slightly longer than prostomium. Peristomium similar in length to following segments, covering dorsally posterior end of prostomium; tentacular cirri papilliform. Dorsal cirri papilliform, shorter than parapodial lobes, smaller than lateral antennae but slightly larger than tentacular cirri, absent on chaetiger 2 (Fig. 67A). Compound chaetae with smooth, thick shafts, thicker and becoming more angular posteriorly; blades short, bidentate, subdistal tooth small, well separated from distal tooth on posterior parapodia, with short marginal spines on anterior parapodia (Fig. 67D), smooth on posterior parapodia (Fig. 67F), all similar in length, about 9–8 µm. Anterior parapodia each with about 8 compound chaetae, numbers diminishing progressively posteriorly to 3 on posterior parapodia. Dorsal simple chaetae from chaetiger 1, slender anteriorly, bidentate, with short subdistal spines (Fig. 67C), progressively thicker, distinctly thick posteriorly, smooth, strongly bidentate, both teeth similar and strong, widely separated from each other (Fig. 67E). Ventral simple chaetae from chaetiger 24 in holotype, thick, similar to dorsal simple chaetae (Fig. 67G). Pharynx short, through about 4–5 segments, pharyngeal tooth long, on anterior rim (Fig. 67A). Proventricle similar in length to pharynx, through about 4 segments, with 18 muscle cell rows.

Remarks. Exogone (Parexogone) wilsoni n.sp. is similar to E. (P.) hebes from Atlantic coasts of North America and Europe; E. (P.) wilsoni , however, has proportionally longer median antenna and the chaetae, although similar, are different, with smaller proximal tooth and some spines on the margin (see San Martín, 2003). Exogone (P.) parahomoseta Hartmann-Schröder, 1974b , from South Africa, as well as its subspecies mediterranea from the Mediterranean Sea, have the dorsal simple chaetae marginally serrated, and the blades of compound chaetae are provided with long and thick marginal spines (Hartmann-Schröder, 1974b; San Martín, 1984a, 2003). Exogone (Parexogone) breviseta Kudenov & Harris, 1995 , from California, has shorter antennae, proportionally longer blades on the compound chaetae, and lacks compound chaetae with large shafts and short blades, with subdistal tooth well separated from distal tooth, smooth on margin (see Kudenov & Harris, 1995); in addition, the dorsal and ventral simple chaetae are not as thick as those present in E. (P.) wilsoni .

Distribution. Australia (Victoria, New South Wales).

Habitat. Sand, 4–22 m depth.

Etymology. The species is named in honour of Dr Robin Wilson, of the Museum of Victoria.