Marine Flora and Fauna of Hong Kong and Southern China IV

Additional notes on the taxonomy of the marine Oligochaeta of Hong Kong with a description of a new species of Tubificidae

The Marine Flora and Fauna ofHong Kong and Southern China IV (ed. B. Morton). Proceedings of the Eighth International Marine Biological Workshop: The Marine Flora and Fauna of Hong Kong and Southern China, Hong Kong, 2-20 April 1995. Hong Kong: Hong Kong University Press, 1997. ADDITIONAL NOTES ON THE TAXONOMY OF THE MARINE OLIGOCHAETA OF HONG KONG, WITH A DESCRIPTION OF A NEW SPECIES OF TUBIFICIDAE C. Erseus Department of Invertebrate Zoology, Swedish Museum of Natural History, Box 50007, SE-I04 05 Stockholm, Sweden ABSTRACT Six species of Tubificidae are described from Hong Kong for the first time. One, Gianius eximius sp.nov., is new to science. It is characterized by multiple penial setae arranged in cone-shaped bundles, heavily muscular atria and the unusual position of the spermathecal pores in segment XI, i.e., the same segment as that of the male pores. This species, as well as Aktedrilus floridensis Erseus, Limnodriloides pierantonii (Hrabe), L. iateroporus Erseus and an unnamed, papillated, species of Tectidrilus, are recorded from the Cape d' Aguilar Marine Reserve, at the southeastern corner of Hong Kong Island. The sixth species, Ainudrilus geminus Erseus, is reported from the island of Sha Chau in the northwestern New Territories. With these additions, a total of 71 species of marine and brackishwater Oligochaeta are known from Hong Kong. A complete checklist of all these taxa are provided as an appendix to the paper. INTRODUCTION The marine oligochaetes of Hong Kong have been treated in a series of taxonomic papers (Erseus 1984, 1990a, 1992a). Fifty-two species of Tubificidae, three Naididae, nine Enchytraeidae and one Megascolecidae have been recorded from the Hong Kong area to date. The present contribution provides supplementary records and taxonomic descriptions of six species of Tubificidae, on the basis of material collected during April 1995. One new taxon, Gianius eximius sp.nov., is described. A checklist of all marine and brackishwater Oligochaeta known from Hong Kong is provided as an appendix to the paper. For a complete account of all oligochaetes collected in the Cape d'Aguilar Marine Reserve during April 1995, see Erseus and Diaz (1997). 38 C.ERSEUS NOMENCLATURAL CHANGES In a previous supplement to Hong Kong's marine Oligochaeta (Erseus 1992a:157-158), Phallodrilus vanus Erseus, 1984, and P. darvelli Erseus, 1984 were (by lapsus calami) referred to the genus Pectinodrilus Erseus, 1992; these species are currently regarded as members of Pacifidrilus Erseus, 1992 (Erseus 1992b). MATERIALS AND METHODS Qualitative sediment samples were collected from intertidal and subtidal marine habitats in the Cape d'Aguilar Marine Reserve, at the southeastern corner of Hong Kong Island. For the subtidal stations, assistance was provided by SCUBA-divers. The divers shuffled sediments into either a plastic bag or a jar. At the intertidal sites, sediments were dug up by hand by the author. The study also includes one intertidal sample collected at the island of Sha Chau in the northwestern New Territories, by Prof. R. Gibson (Liverpool). All samples were stirred repeatedly with seawater and the suspensions decanted into a 0.25 !lID sieve. Sieved fractions were examined under a dissecting microscope and oligochaetes were removed and fixed in Bouin's fluid. Almost exclusively, only sexually mature worms were selected, because juvenile oligochaetes are either difficult or impossible to identify to species. The specimens were later transferred to 70 % ethanol, stained in alcoholic paracarmine, dehydrated through a graded ethanol/xylene series, and finally mounted whole in Canada balsam. The types and other reference material are deposited in the Swedish Museum of Natural History (SMNH), Stockholm, Sweden. Measurements in the descriptions refer to the mounted, somewhat compressed, worms. ABBREVIATIONS USED IN THE FIGURES a atrium aa atrial ampulla ad atrial duct msd muscular part of spermathecal duct p penis pp pseudopenis ppa prostatic pad pps pseudopenial sac pr prostate gland pr 1 anterior prostate gland pr 2 posterior prostate gland ps penial seta s spermatheca sa spermathecal ampulla sd spermathecal duct sf sperm funnel HONG KONG MARINE OLIGOCHAETA sv spermathecal vestibule vd vas deferens SYSTEMATIC ACCOUNT TUBIFICIDAE RHYACODRILINAE Ainudrilus Finogenova, 1982 Ainudrilus geminus Erseus, 1990b Figure 1 Ainudrilus geminus Erseus, 1990b, pp. 247-248, fig. 2. 39 New material. SMNH Main colI. 1480, 1 specimen from Sha Chau, an island in the northwestern part of the New Territories: at the sothern end of the northern part of the island (north end of the sand bar connecting the two parts), low water level, boulders with...