Sthenelais fusca Johnson, 1897

Muir, Alexander I. & Bamber, Roger N., 2008, New polychaete (Annelida) records and a new species from Hong Kong: the families Polynoidae, Sigalionidae, Chrysopetalidae, Pilargiidae, Nereididae, Opheliidae, Ampharetidae and Terebellidae, Journal of Natural History 42 (9 - 12), pp. 797-814 : 800-801

Sthenelais fusca Johnson, 1897

Material

One specimen, control Station Z, Long Kei Wan, off the mouth of Conic Island Cave , Hong Kong, 22 ° 229030 N 114 ° 229080E; sediment 1% gravel, 96% sand, 3% silt/ clay, depth 13.7 m; water temperature 26 ° C .

Two species of Sthenelais have been recorded from Hong Kong waters. Shin (1982) reported S. boa (Johnston, 1833) from the West Lamma Channel; Mackie et al. (1993) reported S. nami Gallardo, 1967 , from the Tolo Channel. Wu et al. (1997) have recorded S. fusca Johnson, 1897 , from the intertidal zone of the Yellow Sea. Unfortunately, partial revision of this genus by Pettibone (1971a) did not consider any of these species.

Sthenelais boa has been redescribed by Chambers and Muir (1997). It has Berwick Bay (northeastern England) as its type locality, but has been reported from the Atlantic Ocean and Indo-Pacific areas ( Chambers and Muir 1997). Hartmann- Schröder (1996) describes it as cosmopolitan apart from the Arctic and Antarctic. Sthenelais fusca has been redescribed by Pettibone (1971b): it has three locations in California, USA, as its type locality, and has been reported from Central California to Peru ( Pettibone 1971b) and Japan and the Yellow Sea ( Wu et al. 1997). Sthenelais nami was described by Gallardo (1967) from Nha Trang, Vietnam, and, as stated above, has also been reported from Hong Kong.

The present specimen agrees in most respects with the description of S. fusca by Pettibone (1971b). She states (p. 1394) that the scales are ‘‘rusty brown, mottled with dark pigment, and sometimes with darker crescent-shaped areas medial to elytrophores’’. On the present example, the scales are clear on the distal half (near the marginal papillae), light brown on the proximal half (near the mid-line of the body) and have a dark grey-brown marking along the posterior margin. This may represent individual or regional variation.

The three Hong Kong species can be separated using the following key. However, as the genus has never been completely revised, identifications should always be checked against reliable descriptions.

1. Elytra with about three submarginal rows of papillae on the upper surface as well as a marginal fringe. Neurochaetae include a few unjointed, with whorls of spines................... Sthenelais fusca

- Elytra with marginal fringe only. Unjointed neurochaetae with whorls of spines present or absent.................................... 2

2. Neurochaetae include a few unjointed, with whorls of spines. Neuropodium has posterior bract ventrally with row of stylodes................................................ Sthenelais boa

- Neurochaetae all jointed. Neuropodium with two elongate papillae (one dorsal, one ventral) near tip...................... Sthenelais nami