Hyun Soo Rho

First Molecular Data on the Phylum Loricifera - An Investigation into the Phylogeny of Ecdysozoa with Emphasis on the Positions of Loricifera and Priapulida

Abstract Recent progress in molecular techniques has generated a wealth of information for phylogenetic analysis. Among metazoans all but a single phylum have been incorporated into some sort of molecular analysis. However, the minute and rare species of the phylum Loricifera have remained elusive to molecular systematists. Here we report the first molecular sequence data (nearly complete 18S rRNA) for a member of the phylum Loricifera, Pliciloricus sp. from Korea. The new sequence data were analyzed together with 52 other ecdysozoan sequences, with all other phyla represented by three or more sequences. The data set was analyzed using parsimony as an optimality criterion under direct optimization as well as using a Bayesian approach. The parsimony analysis was also accompanied by a sensitivity analysis. The results of both analyses are largely congruent, finding monophyly of each ecdysozoan phylum, except for Priapulida, in which the coelomate Meiopriapulus is separate from a clade of pseudocoelomate priapulids. The data also suggest a relationship of the pseudocoelomate priapulids to kinorhynchs, and a relationship of nematodes to tardigrades. The Bayesian analysis placed the arthropods as the sister group to a clade that includes tardigrades and nematodes. However, these results were shown to be parameter dependent in the sensitivity analysis. The position of Loricifera was extremely unstable to parameter variation, and support for a relationship of loriciferans to any particular ecdysozoan phylum was not found in the data.

Phylogeny of Kinorhyncha Based on Morphology and Two Molecular Loci

The phylogeny of Kinorhyncha was analyzed using morphology and the molecular loci 18S rRNA and 28S rRNA. The different datasets were analyzed separately and in combination, using maximum likelihood and Bayesian Inference. Bayesian inference of molecular sequence data in combination with morphology supported the division of Kinorhyncha into two major clades: Cyclorhagida comb. nov. and Allomalorhagida nom. nov. The latter clade represents a new kinorhynch class, and accommodates Dracoderes, Franciscideres, a yet undescribed genus which is closely related with Franciscideres, and the traditional homalorhagid genera. Homalorhagid monophyly was not supported by any analyses with molecular sequence data included. Analysis of the combined molecular and morphological data furthermore supported a cyclorhagid clade which included all traditional cyclorhagid taxa, except Dracoderes that no longer should be considered a cyclorhagid genus. Accordingly, Cyclorhagida is divided into three main lineages: Echinoderidae, Campyloderidae, and a large clade, ‘Kentrorhagata’, which except for species of Campyloderes, includes all species with a midterminal spine present in adult individuals. Maximum likelihood analysis of the combined datasets produced a rather unresolved tree that was not regarded in the following discussion. Results of the analyses with only molecular sequence data included were incongruent at different points. However, common for all analyses was the support of several major clades, i.e., Campyloderidae, Kentrorhagata, Echinoderidae, Dracoderidae, Pycnophyidae, and a clade with Paracentrophyes + New Genus and Franciscideres (in those analyses where the latter was included). All molecular analyses including 18S rRNA sequence data furthermore supported monophyly of Allomalorhagida. Cyclorhagid monophyly was only supported in analyses of combined 18S rRNA and 28S rRNA (both ML and BI), and only in a restricted dataset where taxa with incomplete information from 28S rRNA had been omitted. Analysis of the morphological data produced results that were similar with those from the combined molecular and morphological analysis. E.g., the morphological data also supported exclusion of Dracoderes from Cyclorhagida. The main differences between the morphological analysis and analyses based on the combined datasets include: 1) Homalorhagida appears as monophyletic in the morphological tree only, 2) the morphological analyses position Franciscideres and the new genus within Cyclorhagida near Zelinkaderidae and Cateriidae, whereas analyses including molecular data place the two genera inside Allomalorhagida, and 3) species of Campyloderes appear in a basal trichotomy within Kentrorhagata in the morphological tree, whereas analysis of the combined datasets places species of Campyloderes as a sister clade to Echinoderidae and Kentrorhagata.

Triodontoderes anulap gen. et sp. nov.—a new cyclorhagid kinorhynch genus and species from Micronesia

A new kinorhynch genus and species is described from coralline sand collected on the atoll of the Chuuk Islands, Micronesia. The new genus and species, Triodontoderes anulap gen. et sp. nov., is characterized by having an introvert with only five scalid rings, segment 1 consisting of one tergal and one sternal plate, segments 2 to 4 of one tergal and two sternal plates, and segments 5 to 11 of one tergal plate with midventral articulation. Triodontoderes anulap gen. et sp. nov. shares several characters with species of Zelinkaderes , including reduced number of scalid rings, distally tripartite placids, a trunk being circular in cross-section, and segments 5 to 10 being composed of a single tergal plate with midventral articulation. Until the kinorhynch relationships have been examined in a formal phylogenetic analysis, Triodontoderes gen. et sp. nov. are tentatively assigned to Zelinkaderidae.

Occurrence of the newly described kinorhynch genus Meristoderes (Cyclorhagida: Echinoderidae) in Korea, with the description of four new species

Meristoderes is the most recently described kinorhynch genus and has until now only accommodated its type species M. macracanthus from the Mediterranean and M. galatheae from the Solomon Islands in Southeast Asia. The present contribution is an account on the genus based on samples from the ongoing exploration of the kinorhynch fauna in coastal and subtidal waters around in the Korean Peninsula. The samples yielded no less than five new species of Meristoderes, of which four are formally described herein, whereas only diagnostic notes are provided for the fifth. The descriptions are supplemented with a key to species of the genus, and morphological notes on the organization of cephalic structures and cuticular trunk structures. New morphological findings include intrageneric variation in the composition of the terminal segment, which may have either one unpaired or two paired tergal plates. The data also show that the differentiation of a tergal and sternal plate in segment 2 varies greatly between the species. Results of the present study indicate that the genus probably holds a significant, unrecovered biodiversity, but the data also shed light on potential future taxonomic problems among genera of Echinoderidae and stress the importance of identifying additional diagnostic traits to define Meristoderes.

A New Species of Condyloderes (Cyclorhagida, Kinorhyncha) from Korea

A new kinorhynch species, Condyloderes megastigma sp. nov., is described from the Korea Strait. The new species is characterized by the presence of 16 placids with either eight, four, or two knobby projections, middorsal and lateroventral acicular spines on segments 1 to 9, lateroventral cuspidate spines on segment 2 in females only, but otherwise lateroventral cuspidate spines on segments 4 and 5, and 8 and 9 in both sexes. Unique for the new species is furthermore the presence of paired ventromedial appendages on segments 7 and 8, giant ventromedial sensory spots on segment 9, and a terminal segment consisting of one tergal and one sternal plate. The mouth cone and introvert armature are described in detail for the first time for the genus Condyloderes Higgins, 1969. This study reveals similarities in several morphological characters between this genus and species of Campyloderes Zelinka, 1913.

New Data on the Genus Paracentrophyes (Homalorhagida, Kinorhyncha), with the Description of a New Species from the West Pacific~!2010-01-06~!2010-04-21~!2010-05-18~!

The kinorhynch genus Paracentrophyes currently consists of two species only: P. quadridentatus (Zelinka, 1928) from the Mediterranean Sea and P. praedictus Higgins, 1983 from Belize in the Caribbean. Both species have until now been recorded from their type localities only. In the present contribution a new species of Paracentrophyes, P. anurus sp. nov., is described from the Korea Strait. The species can be recognized by details in the mouth cone morphology, absence of perispinal setae in segment 10, and absence of a midterminal process in both sexes. Female specimens are furthermore characterized by the presence of an extraordinary long middorsal spine on segment 10, whereas males possess a midterminal type 3 sensory spot. Besides the recording of the new species, the occurrence of P. cf. quadridentatus is reported from two localities in the Atlantic Ocean (Faeroe Islands and Spain). The recorded specimens are described in detail, based on combined examinations with LM and SEM, and diagnostic traits for all three species of Paracentrophyes are discussed in light of the newly acquired information. Furthermore, an emended terminology for positions of cuticular trunk structures is proposed.

A new species of the rare genus Sphenoderes (Cyclorhagida, Kinorhyncha), with differential notes on S. indicus Higgins, 1969

Abstract A new species of the rarely recorded kinorhynch genus Sphenoderes was collected in the Korea Strait and East China Sea. The new species, Sphenoderes poseidon sp. nov., is distinguished by the presence of lateroventral cuspidate spines on segments 5 and 9 only, opposed to cuspidate spines on segments 5, 8 and 9 as found in S. indicus. The new species is furthermore characterized by having the special head aperture that is diagnostic for species of Sphenoderes, but yet possessing a segment 1 composed of a single, closed cuticular ring, rather than a dorsal, a ventral and two lateral plates as found in S. indicus. The description of Sphenoderes poseidon sp. nov. includes the first scanning electron microscopical examinations of cuticular details in a species of Sphenoderes. The new information is discussed and a comparison is made with the putative closely-related species S. indicus, as well as with other species more generally across the Kinorhyncha.

On the genus Dracoderes Higgins & Shirayama, 1990 (Kinorhyncha: Cyclorhagida) with a redescription of its type species, D. abei, and a description of a new species from Spain

Abstract The type species of Dracoderes, D. abei, is redescribed based on specimens from several localities in Japan and Korea, and a new species of the genus, Dracoderes gallaicus sp. nov., is described from the coast of Spain in Western Europe. The new species is distinguished by the presence of lateral accessory spines on segment 5. In addition, preliminary diagnostic notes on a yet undescribed species from the Okinawa Region, Dracoderes sp. 1, are provided. Based on new information from D. abei and D. gallaicus sp. nov., an emended genus diagnosis for Dracoderes is proposed. The study includes the first scanning electron microscopical data for species of Dracoderes, and presents for the first time detailed information about head morphology and scalid arrangement, new data about the arrangement of the neck placids, and demonstrates the presence of feebly visible nephridial pores. The new information may be of phylogenetic significance, and is expected to contribute important data for future phylogenetic analyses of the kinorhynch interrelationships.

Tenuidraconema koreensis, a new species of marine nematodes (Adenophorea: Desmodorida) from South Korea

Tenuidraconema koreensis, a new species of free‐living marine nematodes, collected from the subtidal coarse sediments and various invertebrates of Namae, is described. The new species differs from T. fiersi Decraemer, 1989, the only other species in the genus, by having the combination of the following characters: the position of twelve cephalic adhesion tubes in both sexes (anterior six cephalic adhesion tubes inserted on the rostrum and posterior six inserted on the body annules), and the number of posterior sublateral adhesion tubes (12 in male and 13 in female) and posterior subventral adhesion tubes (15 in male and 19 in female). This paper contains the description of the new species with illustrations and scanning electron microscope (SEM) photomicrographs. This is the first discovery of the monotypic genus Tenuidraconema outside the type locality.

Zelinkaderes yong sp. nov. from Korea - the first recording of Zelinkaderes (Kinorhyncha: Cyclorhagida) in Asia

BackgroundA new kinorhynch species, Zelinkaderes yong sp. nov., is described from Korea.ResultsZelinkaderes yong sp. nov. is described from coastal, sandy habitats in Korea by means of light and scanning electron microscopic techniques. The new species is characterized by the presence of cuspidate spines in lateroventral positions on segments 2 and 9, ventrolateral positions on segment 5, and lateral accessory positions on segment 8; flexible tiny acicular spines in lateroventral positions on segment 2, more regular-sized lateroventral acicular spines on segment 8, and middorsal spines on segments 4, 6, 8, 9, and 11. Females furthermore have acicular spines in middorsal and midlateral positions on segment 10, whereas males have crenulated spines on this segment. The absence of acicular spines in the lateral series of segment 9 makes it easy to distinguish the new species from all previously described congeners. The new species differs most from Zelinkaderes submersus, whereas it is morphologically closest to Zelinkaderes klepali. In regard to the spine patterns, the new species only differs from Z. klepali by its lack of lateroventral acicular spines on segment 9.ConclusionsThe finding of a new species of Zelinkaderes in East Asia extends the distributional range of the genus, which suggests that the genus basically could be present anywhere in the world and could be considered as cosmopolitan.