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Marine Macrodasyida (Gastrotricha) from Hokkaido, Northern Japan

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Marine Macrodasyida (Gastrotricha) from Hokkaido, Northern Japan Species Diversity 23: 183–192 25 November 2018 DOI: 10.12782/specdiv.23.183 Marine Macrodasyida (Gastrotricha) from Hokkaido, Northern Japan Shohei Yamauchi1 and Hiroshi Kajihara2,3 1 Department of Natural History Sciences, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan 2 Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan E-mail: [email protected] (HK) 3 Corresponding author (Received 13 November 2017; Accepted 20 July 2018) http://zoobank.org/3FA0A429-1676-4326-B8D3-FFBA8FE403C9 Three new species of macrodasyidan gastrotrichs are described from the coasts of Hokkaido, northern Japan. Cephalodasys mahoae sp. nov. differs from congeners in having the oocytes developing from posterior to anterior. Turbanella cuspidata sp. nov. is characterized by a pair of small, ventrolateral projective organs at U06. Turbanella lobata sp. nov. is unique among congeners in having paired lateral lobes on the neck. We inferred the phylogenetic position of C. mahoae sp. nov. by maximum-likelihood analysis and Bayesian inference based on 18S rRNA, 28S rRNA, and COI gene sequences from 28 species of macrodasyids. In the resulting trees, C. mahoae sp. nov. formed a clade with an unidentified species of Cephalodasys Remane, 1926, but not with C. turbanelloides (Boaden, 1960). Key Words: Interstitial, marine invertebrates, meiofauna, Pacific, Sea of Japan. 1924, and described Paradasys nipponensis Sudzuki, 1976. Introduction Considering the rather inadequate description and illustra- tion, seemingly based on juvenile specimens, however, there The phylum Gastrotricha currently contains about 850 is little doubt that P. nipponensis must be regarded as species species of aquatic, microscopic animals (e.g., Todaro et al. inquirenda (Chang et al. 2002). Chang et al. (2002) later de- 2014; Kolicka et al. 2017), which are classified into the two scribed three species of macrodasyidans—Tetranchyroderma orders Chaetonotida and Macrodasyida. The former in- schizocirratum Chang, Kubota and Shirayama, 2002, Thau- cludes tenpin-shaped, hermaphroditic or parthenogenetic mastoderma clandestinum Chang, Kubota and Shirayama, species found in marine, brackish, or freshwater habitats, 2002, and Oregodasys itoi Chang, Kubota and Shirayama, whereas the latter includes vermiform, hermaphroditic 2002—from Shirahama, middle Honshu, Japan. Hiruta species living interstitially in sand in marine ecosystems (2002) mentioned undetermined macrodasyidans from Es- (Hummon and Todaro 2010; Kieneke and Schmidt-Rhaesa ashi, Hokkaido. More recently, Lee and Chang (2011) de- 2015), with exceptions of two freshwater species (Todaro scribed two species—Lepidodasys laeviacus Lee and Chang, et al. 2012). Macrodasyida currently comprises 365 species 2011 and L. tsushimaensis Lee and Chang, 2011—from classified in 35 genera and 10 families (Hummon and To- Tsushima Island in the Korea Strait, between the Japanese daro 2018). Morphologically, macrodasyidans can be distin- mainland and the Korean Peninsula. guished from chaetonotidans by having two pores on each During the course of a faunal survey of marine interstitial side of the pharynx that allow excess water to be drained animals around Hokkaido, we found three species of macro- during feeding; macrodasyidans possess tubular adhesive dasyidans that are new to science, one in Cephalodasys and glands on both anterior and posterior ends of the body as the other two in Turbanella Schultze, 1853. We inferred the well as on the lateral surfaces, as opposed to chaetonotidans phylogenetic position of the new species of Cephalodasys in which adhesive glands are present only on the posterior within Macrodasyida by using partial 18S rRNA, 28S rRNA, end of the body (e.g., Ruppert 1991). and COI gene sequences. In this paper, we describe and il- Macrodasyidans have been poorly investigated in Japan, lustrate these three species, and present the results of the with seven named species so far reported, and only a few re- molecular phylogenetic analysis. cords of undetermined species exist for Hokkaido, northern Japan. Saito (1937) described the first macrodasyidan from Japan, Tetranchyroderma dendricum Saito, 1937, from Hiro- Materials and methods shima. In an investigation of meiofauna around Kasado Is- land in the Seto Island Sea, Sudzuki (1976) detected five gas- Specimen collection. Specimens were collected from trotrich species, including undetermined species in the gen- 2012 to 2014 in the intertidal zone at low tide on three era Cephalodasys Remane, 1926 and Macrodasys Remane, beaches around Hokkaido, Japan (Fig. 1). Sediments at the © 2018 The Japanese Society of Systematic Zoology 184 S. Yamauchi and H. Kajihara ground-water level were sampled with a scoop and taken tant was sieved through 30-µm mesh; the residue was im- back to the laboratory. Animals were extracted by fresh- mediately placed in seawater; and living macrodasyidans water-shock: the sediment was placed in a bucket with tap were collected under a Nikon SMZ-10 stereomicroscope water, then agitated briefly (~10 sec) 2–3 times; the superna- and anaesthetized in a MgCl2 solution isotonic with sea- water (~30 psu). Some of the relaxed living specimens were mounted on a glass slide with a cover slip, examined under an Olympus BX51 light microscope, and photographed with a Nikon DS-5Mc digital camera system at several focal depths. Drawings were made from these images by using the GNU image manipulation program GIMP ver. 2.8. Some of the relaxed specimens were fixed in 10% formalin–seawater and mounted in glycerin on a glass slide, with the edges of the coverslip sealed with Canada balsam. Other specimens were observed by scanning electron microscopy (SEM). Ma- terial for SEM was fixed overnight in Bouin’s solution. After dehydration in a graded ethanol series (50–100%; 30 min each concentration), the specimens were dried in a Hitachi HCP-2 CO2 critical-point drier, mounted on stubs, coated with gold in a JEOL JFC-1100 ion sputter coater, and exam- ined with a Hitachi S-3000N scanning electron microscope at 15 kV accelerating voltage. Type material has been depos- Fig. 1. Map of Hokkaido, showing three sampling localities in ited in the Invertebrate Collection at the Hokkaido Univer- this study: Ishikari, Mukawa, and Higashi-Shizunai. sity Museum (ICHUM), Sapporo, Japan. Table 1. List of gastrotrich taxa used in the molecular analysis with GenBank accession numbers. Species 18S 28S COI Reference Acanthodasys aculeatus JF357639 JF357687 — Todaro et al. (2011) Anandrodasys agadasys JN203487 — — Todaro et al. (2012) Cephalodasys mahoae sp. nov. LC018992 LC383934 LC383935 present study Cephalodasys turbanelloides AM231776 — — Todaro et al. (2006) Cephalodasys sp. 1 AY963691 — — Petrov et al. (2007) Crasiella sp. 1 JN203488 — — Todaro et al. (2012) Crasiella sp. 2 JF970237 — — Papas and Riutort (2012) Dactylopodola typhle JF357653 JF357701 JF432038 Todaro et al. (2011) Diplodasys ankeli JF357667 — JF432049 Todaro et al. (2011) Dolichodasys sp. AM231778 — — Todaro et al. (2006) Lepidodasys unicarenatus JF357665 — JF432039 Todaro et al. (2011) Macrodasys buddenbrocki AY963692 KF921012 — 18S, Petrov et al. (2007); 28S, Petrov et al. (unpublished) Megadasys sp. 1 JF357656 JF357704 — Todaro et al. (2011) Megadasys sp. 2 JF357655 JF357703 — Todaro et al. (2011) Mesodasys littoralis JF357658 JF357706 JF432044 Todaro et al. (2011) Oregodasys tentaculatus JF357626 JF357674 JF432021 Todaro et al. (2011) Paradasys sp. AM231781 — — Todaro et al. (2006) Paraturbanella teissieri JF357661 JF357709 — Todaro et al. (2011) Pleurodasys helgolandicus JF970236 — — Papas and Riutort (2012) Ptychostomella tyrrhenica JF357634 JF357682 JF432027 Todaro et al. (2011) Redudasys fornerise JN203489 — KJ950122 Todaro et al. (2012) Tetranchyroderma thysanophorum JF357646 JF357694 JF432034 Todaro et al. (2011) Thaumastoderma moebjergi JF357671 JF357713 — Todaro et al. (2011) Turbanella bocqueti JF357662 JF357710 JF432046 Todaro et al. (2011) Urodasys sp. 1 DQ079912 — — Sørensen et al. (2006) Urodasys sp. 2 AY218102 — — Giribet et al. (2004) Xenodasys riedli JN203490 — — Todaro et al. (2012) Xenodasys sp. AY228133 — — Giribet et al. (2004) Outgroups Xenotrichula intermedia JF357664 JF357712 JF432048 Todaro et al. (2011) Xenotrichula velox JN185488 JN185529 — Kånneby et al. (2012) Three species of Macrodasyida from Hokkaido 185 DNA extraction and amplification. DNA was extracted of tree lengths=340.20; potential scale reduction factor of from 80 pooled specimens of Cephalodasys mahoae sp. nov. tree lengths=1.009). Run convergence was also assessed with collected from Ishikari beach by using a DNeasy Blood & Tracer ver. 1.7 (Rambaut et al. 2018); effective sample sizes Tissue Kit (QIAGEN). Amplification of partial 18S rRNA, for all parameters were above 200. 16S rRNA, and COI genes was carried out using universal Abbreviations and conventions. Morphological symbols primers: 1F/9R (Giribet et al. 1996) for 18S; 16sar-L/16sbr-H and conventions follow those of Hummon (2010): L, length; (Palumbi et al. 1991) for 16S; LCO1490/HCO 2980 (Folmer H, height; Lt, total body length from anterior tip of head to et al. 1994) for COI. For 28S rRNA gene amplification, the posterior tip of caudum and its adhesive tubes; PhJIn, junc- primer pair 28Sa (Whiting et al. 1997) and 28S_3KR (Yama- tion between pharynx and intestine; LPh, pharyngeal length saki et al. 2013) were used. Reactions were performed with from anterior tip of head to PhJIn; TbA/TbL/TbD/TbDL/ an iCycler
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