Echinoderes aspinosus Sørensen &amp; Rho &amp; Min &amp; Kim &amp; Chang 2012, sp. nov.
Creators: name: Sørensen, Martin V.
name: Rho, Hyun Soo
name: Min, Won-Gi
name: Kim, Dongsung
name: Chang, Cheon Young
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Kinorhyncha
Cyclorhagida
Echinorhagata
Echinoderidae
Echinoderes
Echinoderes aspinosus

description: <i>Echinoderes aspinosus</i> sp. nov. (Figures 2–3, Table 2) <b>Diagnosis.</b> <i>Echinoderes</i> without tubules or spines, except lateral terminal ones. Both sexes with rather thin lateral terminal spines; females furthermore with extremely thin lateral terminal accessory spines. Pectinate fringe on ventral side of segments 2 to 5 very strong and obliquely orientated, pointing towards the midventral line. Sieve plates on segment 9 elongate and narrow, reaching almost 50% of the total segment length. <b>Type material.</b> Holotype: adult female, collected on 31 March 2001, at station CYC-23, Yeonpyeong Island off the Korean west coast, (Fig. 1A), 37 o 39.05’N 125 o 41.43’E, Korea, from subtidal sand, mounted in glycerine, deposited at NIBR under accession number INBRIV0000245081. Allotype: adult male, same collecting data as holotype, mounted in glycerine, deposited at NHMD under accession number ZMUC KIN-538. No specimens were available for examination with SEM. <b>Etymology.</b> The species name is composed of the Latin <i>a</i> - (no or lacking) and - <i>spina</i> (spine), meaning the one without spines, with reference to the complete absence of spines on segments 1 to 10. <b>Description.</b> Adult specimens consist of a head, a neck and eleven trunk segments (Figs 2A–B, 3D). Measurements and dimensions are given in Table 2. A table summarizing sensory spots, spines, and glandular cell outlet positions is not provided, since such structures apparently are absent (or could at least not be identified) on most of the animal. Because no specimens were available for SEM examinations, it was not possible to identify minor cuticular structures such as sensory spots and pore fields. Hence, not mentioning these structures in the description should not be understood as a positive confirmation of their absence. The head consists of a retractable mouth cone and an introvert. Inner and outer armature could not be examined in detail. The pharynx of the holotype was strongly protruded though, revealing the presence of a pharyngeal crown (Fig. 3A). The neck consists of 16 placids, all measuring 18 µm in length and 10 µm in width at bases (Figs 2A, 3B), except midventral placid that measures 16 µm in width (Figs 2B, 3C). If the midventral placid is number 1, and other placids are numbered clockwise from this one, placids number 2 and 16 have broad trichoscalid plates, whereas smaller, but rather elongate trichoscalid plates are associated with placids number 6, 8, 10 and 12 (Figs 2A, 3B). Segment 1 consists of one complete cuticular ring (Figs 2A–B, 3B–C). Sensory spots or pore fields could not be identified with certainty. Cuticular hairs emerge through rounded perforation sites, and are densely scattered over the posterior half of the segment, down to the IJ-line. Posterior margin with well-developed pectinate fringe. Segment 2 consists of one complete cuticular ring. Cuticular hairs are distributed in a median belt around the segment, limited posteriorly by the IJ-line. Posterior segment margin with regular pectinate fringe on dorsal side, but a conspicuously strong fringe ventrally; fringe tips within the ventromedial areas are obliquely orientated, pointing towards the midventral line (Figs 2C, 3C). Segment 3, and following 8 segments, consist of one tergal and two sternal plates (Figs 2B, 3B). Spines, tubules, glandular cell outlets type 1 or 2 are not present. Cuticular hairs are densely distributed in a median belt around the segment, except in paraventral areas, limited posteriorly by the IJ-line. Posterior margin with regular pectinate fringe on dorsal side, and a conspicuously strong one on ventral side; fringe tips on sternal plates of segments 3 to 5 are obliquely orientated, pointing towards the midventral line (Figs 2B, 3E); fringe tips on sternal plates of following segment not oblique and less prominent (Figs 2B, 3F). Segment 9 similar to preceding segments, but with weaker pectinate fringe, and a pair of very conspicuous sieve plates (Figs 2B, 3F). The sieve plates are elongate, 27 µm long, i.e. almost 50% of segment length, and rather narrow, but broadens slightly in each end. Segment 10 generally as preceding segments, but with the posterior margins of the sternal plates forming a broadly lobed midventral extension that almost covers the ventral side of the terminal segment (Fig. 2B). Segment 11 with long and rather thin lateral terminal spines. Females furthermore with pair of very thin lateral terminal accessory spines (Figs 2A–B, 3G). Males with three pairs of flexible penile spines; dorsalmost spine thick, ca. 30 µm long, median penile spine slightly thinner and pointed, ca. 26 µm, ventralmost penile spine thicker, ca. 41 µm (Figs 2C–D, 3H). Cuticular hairs are not present. Tergal extensions are short, with interrupted mesial margins (Fig. 3G); sternal extensions short and lobed with weak fringes. A pair of long (23 µm) setae emerges from the outer margins of the tergal extensions (Figs 2A, 3G). <b>Notes on diagnostic features and potential relatives.</b> Due to its complete lack of tubules and spines (except terminal ones), <i>Echinoderes aspinosus</i> <b>sp. nov.</b> cannot be confused with any other species of Echinoderidae. In addition to this negative character, the species can also be recognized by its strong, obliquely orientated pectinate fringe on the ventral side of segments 2 to 5. This character has to our knowledge not been reported from any other kinorhynch species. Another noteworthy character, not unique though, is the enlarged sieve plates. The only species that potentially could be confused with <i>E. aspinosus</i> <b>sp. nov.</b>, are those of the <i>E. coulli</i> -group that also tend to have few, small or completely reduced spines and tubules (Ostmann <i>et al.</i> 2012). This speciesgroup includes, besides <i>E. coulli</i> Higgins, 1977, the following five species: <i>E. maxwelli</i> Omer-Cooper, 1957, <i>E. teretis</i> Brown, 1999 in Adrianov &amp; Malakhov, 1999, <i>E. rex</i>, <i>E. applicitus</i> Ostmann, Nordhaus &amp; Sørensen, 2012, and <i>E. ohtsukai</i> Yamasaki &amp; Kajihara, 2012. Common for all these six species are, besides the reduced spines in terms of number and size, that they all possess a somewhat enlarged sieve plate, and that females do not possess lateral terminal accessory spines (see Higgins 1977; Lundbye <i>et al.</i> 2011, Ostmann <i>et al.</i> 2012, Yamasaki &amp; Kajihara 2012). An enlarged sieve plate is found in <i>E. aspinosus</i> <b>sp. nov.</b> also, and even though females of the species have lateral terminal accessory spines, it is noteworthy that they are very weakly developed. These similarities could indicate a closer relationship between <i>E. aspinosus</i> <b>sp. nov.</b> and species of the <i>E. coulli</i> -group.
description: Published as part of <i>Sørensen, Martin V., Rho, Hyun Soo, Min, Won-Gi, Kim, Dongsung &amp; Chang, Cheon Young, 2012, An exploration of Echinoderes (Kinorhyncha: Cyclorhagida) in Korean and neighboring waters, with the description of four new species and a redescription of E. tchefouensis Lou, 1934 *, pp. 161-196 in Zootaxa 3368 (1)</i> on pages 165-169, DOI: 10.11646/zootaxa.3368.1.8, http://zenodo.org/record/5252292
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