(Loricifera) from Deep-Sea Sediments of Volcanic Origin in the Kilinailau Trench North of Papua New Guinea

Helgol Mar Res (2004) 58:40–53 DOI 10.1007/s10152-003-0167-x ORIGINAL ARTICLE Gunnar Gad A new genus of Nanaloricidae (Loricifera) from deep-sea sediments of volcanic origin in the Kilinailau Trench north of Papua New Guinea Received: 26 March 2003 / Revised: 15 August 2003 / Accepted: 13 October 2003 / Published online: 28 November 2003 Springer-Verlag and AWI 2003 Abstract A new genus and species of Nanaloricidae Introduction (Loricifera), Phoeniciloricus simplidigitatus, is described inhabiting fine sand covered by a layer of volcanic ash at Adult Loricifera are bilaterally symmetrical interstitial a water depth of 1,813 m in the New Ireland Basin near invertebrates around 250 mm long (Kristensen 1991a). the Kilinailau Trench (north of Papua New Guinea). The The body of the adult is divided into a mouth cone, an described specimen is a postlarva enclosed in a larval eversible introvert densely covered with rows of scalids, a exuvium. This is the first report of a species belonging to thorax with a neck region bearing basal plates and the Nanaloricidae from the deep sea. This occurrence is trichoscalids, and an abdominal region armoured with a surprising, because Nanaloricidae are typical inhabitants lorica (Kristensen 2003). The lorica of Nanaloricidae of coarse sands in the intertidal or littoral zone. Preference consists of six or more heavily sclerotized plates with for these shallow water habitats is reflected in many spikes at their anterior rim (Kristensen 1983). Their morphological features which characterize the Nanalori- Higgins-larvae have similar body regions to the adults but cidae, and are not normally found in Loricifera inhabiting clearly differ morphologically. The body of the larva is fine-grained, clayish, deep-sea bottoms. The postlarva of composed of a simpler mouth cone, an introvert covered the new species is characterized by a long narrow mouth with a lower number of short and more hook-like scalids, tube, an urn-shaped lorica divided into ten plates, and 13 a collar as an intermediate region between introvert and small lorica spikes. Distinguishing features of the Hig- thorax, a long and flexible thorax with transverse rows of gins-larva include short spinose toes lacking mucros but plates, and an abdomen with a weakly developed lorica having small and slightly enlarged bases, short scalids on (Kristensen 1991a, 2003). The latter is equipped ventrally the introvert, many thoracic plates arranged in 6–8 rows, with grasping appendages and caudally with long toes for numerous small papillate flosculi in the collar and caudal grasping or locomotion (Kristensen 1991a). Some Lori- regions, and three pairs of filiform, short locomotory ciferan taxa have complex life cycles (Kristensen and appendages on the ventral side. Some features of the new Brooke 2002). Sexes are separate and show a more or less species, especially of the Higgins-larva, are discussed as pronounced sexual dimorphism in the structure of the adaptations to the deep-sea environment. clavoscalids and the copulatory spicule of males. Apart from the larval stages, a juvenile or postlarval stage Keywords Meiofauna · Loricifera · Deep sea · occurs in the life cycle of Nanaloricidae (Kristensen Zoogeography · Expedition SO-133 EDISON II 1991a). The Loricifera is a poorly known meiofauna taxon inhabiting the well-oxygenated uppermost layers of the sediment (Higgins and Kristensen 1988). Loricifera have been found worldwide at depths from 7 m to 8,300 m, i.e. Communicated by R.M. Kristensen in the subtidal zone as well as in the deep sea (Todaro and Kristensen 1998). Since their first description in 1983, G. Gad ()) AG Zoosystematik und Morphologie, only 11 species have been recorded in two families and Fakultt V (fr Mathematik und Naturwissenschaften), three genera (Kristensen 2003). The first species de- Institut fr Biologie und Umweltwissenschaften, scribed was Nanaloricus mysticus Kristensen, 1983, as the Carl von Ossietzky Universitt Oldenburg, representative species of the Nanaloricidae, which was 26111 Oldenburg, Germany discovered in intertidal shell-gravel near the coast of e-mail: [email protected] Roscoff, France (Kristensen 1983). The second species of Tel.: +49-441-7983367 Nanaloricidae, Nanaloricus khaitatus Todaro and Kris- Fax: +49-441-7983162 41 tensen, 1998 was found in a similar interstitial habitat in anoxic sediments of eutrophic bottoms (Vanreusel et al. the Mediterranean Sea (Todaro and Kristensen 1998). 1997). Biological investigations during the cruise SO-133 There are only a few reports of Loricifera from the deep EDISON to the submarine volcanoes of the New Ireland sea (Soetaert et al. 1984; Hubbard et al. 1988; Kristensen Basin concentrated on the study of the benthic fauna and Shirayama 1988). In fact, the first, and to date only, composition at and near hot vents (Herzig 1998). species discovered in the deep sea belongs to the second family of Loricifera, the Pliciloricidae. Pliciloricus hadalis Kristensen and Shirayama, 1988 was found Methods inhabiting red clay 8,260 m deep in the Izu-Ogasawara Trench of the western Pacific (Kristensen and Shirayama Samples were taken during expedition SO-133 EDISON of the R/V 1988). The new species described here is the first report ‘Sonne’ in 1998 around a fracture zone with neighbouring hydrothermal vents at the New Ireland Basin north of Papua New of a Nanaloricidae from the deep sea and from sediments Guinea (see map, Fig. 1) in the Pacific Ocean (Herzig 1998). influenced by volcanic and hydrothermal activity. This The qualitative subsample yielding the species described here occurrence seems to be an exception, because Nanalori- was sample number 63 GKG (022309900N 1525008300E) which had cidae have been assumed to prefer shallow water habitats a volume of 160 cm3 and was taken using a great box corer (GKG) at 1,813 m depth to the north of Lihir Island, near the Kilinailau (Gad 2003; Kristensen and Gad 2003). This is reflected in Trench, an inactive subduction zone (Herzig 1998). Sediments from many morphological features which characterize the sample 63 GKG are grey and brown medium sand covered by a 2- Nanaloricidae and which are normally not found in cm-thick layer of freshly erupted volcanic ash mixed with a few Loricifera inhabiting fine-grained, clayish, deep-sea bot- Foraminifera shells and tiny basaltic pepperites. toms. The sediment, together with the supernatant water, was fixed and preserved in 4% buffered formalin. The sediment was washed Hydrothermalism is limited to restricted areas of out later and filtered through a 40 mm mesh. The meiofauna was tectonic activity throughout the deep-sea floors. In extracted using the differential flotation method with the colloidal contrast to the well-known and intensively investigated silica gel Levasil (density 1,299 g/ml, concentration 40%, Bayer, macrofaunal and bacterial communities of these extreme Leverkusen, Germany), and the sample was centrifuged at 4,000 rpm. The sorted loriciferans were placed in 70% ethanol biotopes, virtually nothing is known about the meiofauna medium, later transferred to glycerol and mounted in glycerin- of hydrothermal vents, nor the sediments influenced by paraffin-beewax preparations (adapted from Higgins and Thiel them (Grassle 1986; Giere 1993). Early studies dealt with 1988), sealed with Glyceel (recipe after Brown 1997). the structure of nematode communities around hydrother- The microscopic investigation was carried out using a Leica interference-microscope (DMLB with UCA condenser, IC prism mal vents, as compared to communities from adjacent and additional magnification 1.5 and 2, Leica microsystems, oxic deep-sea sediments or from the shallow, reduced, Vienna, Austria). Illustrations were made with the aid of a drawing Fig. 1 Regional map of the New Ireland Basin with the Kilinailau Trench and station number 63 (Herzig 1998) 42 tube (mirror technique and macro-apparatus FS25PE, Leica). inner lateral margins of middorsal plate folded upwards Photographs were taken using a computerised digital camera and covering (together with the inner margins of the ColorView-imaging-system (Soft Imaging System, Mnster, Ger- many) system adapted for the DM RXA microscope. The species neighbouring plates) the remaining portion of the was differentiated morphologically. The descriptive terminology is middorsal plate; elements of laterocaudal articulation adapted from Higgins and Kristensen (1986). The type material has (ridges and sockets) of lorical plates in caudal position; been deposited in the type collection of the AG Zoosystematik und anterior rim of lorica with 13 very short spikes; gland Morphologie of the Carl von Ossietzky University Oldenburg. ducts of lorica spikes with small reservoirs; 18 well- developed papillate flosculi in posterior half of lorica; anal cone located more ventrally, covered by a large, Results shield-like, dorsal anal plate. Phoeniciloricus simplidigitatus gen. et sp. nov. Composition Genus diagnosis of Higgins-larva Phylum Loricifera Kristensen, 1983 Last instar larva smaller than postlarva; clavoscalids Family Nanaloricidae Kristensen, 1983 spinose, short, divided into three segments; spinoscalids Type genus Nanaloricus Kristensen, 1983 short, also spinose or weakly modified into hooks; Type species Nanaloricus mysticus Kristensen, 1983 thorax divided into six transverse rows of thoracic Phoeniciloricus gen. nov. plates, dorsally into two additional subrows, plates Type species Phoeniciloricus simplidigitatus sp. nov. folded transversally in

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