Exogone (Sylline) naidinoides Westheide, 1974

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 : 146-147

Exogone (Sylline) naidinoides Westheide, 1974

Figs. 93A–G, 94A–D

Exogone naidinoides Westheide, 1974: 301 , figs. 50, 51 e-f; Russell, 1991: 57, fig. 3.

Exogone (Sylline) naidinoides .–San Martín, 1991a: 737, figs. 11 a– f; Ruíz-Ramírez & Salazar-Vallejo, 2001: 128, fig. 4 (66–76).

Material examined. AUSTRALIA:WESTERN AUSTRALIA. 3 specimens, AM W27429, inshore reef, Ned’s Camp, Cape Range National Park, 21°59'S 113°55'E, very fine sediment and sand from patches in reef, 1 m, H.E. Stoddart, 2 Jan 1984. 26 specimens, AM W27434, limestone reef, off Ned’s camp, Cape Range National Park, 21°59'S 113°55'E, sponge with epiphytic algae, and muddy worm tubes, 1.5 m, R.T. Springthorpe, 2 Jan 1984. 6 specimens (2 specimens on SEM stub), AM W27436, north end of beach, Bundegi Reef, Exmouth Gulf, 21°49'S 114°11'E, rocky rubble, brown algae with epiphytes, sediment, 2 m, H.E. Stoddart, 4 Jan 1984. 5 specimens (2 specimens on SEM stub), AM W27438, 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. 4 specimens (1 specimens on SEM stub), AM W27440, Bush Bay, 30 km south of Carnarvon, 25°10'S 113°39'E, tufted balls of algae on shallow sandflats, 0.5 m, H.E. Stoddart, 6 Jan 1984. 5 specimens, AM W27444, inshore reef off Ned’s Camp, Cape Range National Park, 21°59'S 113°59'E, frilly Caulerpa , 1 m, J.K. Lowry, 2 Jan 1984. 12 specimens, AM W27467, inshore reef off Ned’s Camp, Cape Range National Park, 21°59'S 113°55'E, green algae, 1.5 m, R.T. Springthorpe, 2 Jan 1984. 1 specimen, AM W27679, Bush Bay, 30 km south of Carnarvon, 25°10'S 113°39'E, sand from seagrass beds on shallow sandflats, 0.5 m, H.E. Stoddart, 6 Jan 1984.

Description. Body small, a female carrying juveniles ventrally is 1.5 mm long, 0.08 mm wide, 23 chaetigers. Prostomium ovate, wider than long; 4 eyes in trapezoidal arrangement.Antennae inserted in line anteriorly to anterior eyes; lateral antennae ovate, shorter than prostomium; median antenna longer than lateral antennae, longer than prostomium but shorter than prostomium and palps together (Figs. 93A, 94A ). Palps broad, short, similar in length to prostomium, fused along their length, with dorsal groove and small distal notch (Figs. 93A, 94B ). Peristomium shorter than following segments, usually covering dorsal posterior part of prostomium; tentacular cirri minute, papilliform. Dorsal cirri ovoid, larger than tentacular cirri, absent on chaetiger 2 (Figs. 93A, 94A ). Parapodia of anterior 3 chaetigers each with 3–4 chaetae with blades fused to shafts, reduced to a thick spine, with a crown of shorter spines surrounding tip of shafts (Fig. 93B). Parapodia from chaetiger 4 each with 1 chaeta with a slender, filiform blade, partially fused with shaft, tip of shaft spinose (Fig. 93D), and 2 chaetae with shafts distally spinose; blades fused to shafts, reduced to a thick, short spine (Fig. 93E); only 1 of these chaetae on posterior parapodia. Dorsal simple chaetae from chaetiger 1, distally spinose, ending in acute tip, with a subdistal tooth, provided with a long, distinct inferior spine (Fig. 93C), becoming thicker posteriorly. Ventral simple chaetae from midbody, sigmoid, smooth, bidentate, subdistal tooth longer than distal tooth (Fig. 93F). Acicula solitary, proportionally thick, with a subdistal enlargement (Fig. 93G). Pharynx through 3–4 segments; pharyngeal tooth located on anterior rim (Fig. 93A). Proventricle short, through 2 segments, with about 17 muscle cell rows. Pygidium semi-circular, with 2 long anal cirri.

Remarks. Exogone (Sylline) aquadulcensis Pascual , et al. (1996), from Canary Islands, is similar, but that species has shorter proventricle, the median antenna is proportionally shorter, the dorsal simple chaetae lack the subdistal spine, and the ventral simple chaetae are unidentate (Pascual et al., 1996).

Distribution. Galápagos Islands, Caribbean Sea (Cuba, Belize). Australia (Western Australia).

Habitat. Interstitial in sand and fine sediments, on mangrove roots, dead corals, amongst algae, on shallow water.

Figures

Fig. 94. SEM of Exogone (Exogone) naidinoides. (A) anterior end, dorsal view. (B) anterior end, ventral view. (C) mature female carrying juveniles, ventral view. (D) detail of the juveniles.