Echinoderes komatsui, Yamasaki, Hiroshi & Fujimoto, Shinta, 2014

Yamasaki, Hiroshi & Fujimoto, Shinta, 2014, Two new species in the Echinoderes coulli group (Echinoderidae, Cyclorhagida, Kinorhyncha) from the Ryukyu Islands, Japan, ZooKeys 382, pp. 27-52 : 30-37

Echinoderes komatsui sp. n. [New Japanese name: Komatsu togekawa]Figs 2-6

Material.

Holotype: Adult female (RUMF-ZK-00001), collected on 26 May 2013 at station 1 (Fig. 1A) by Dr H. Komatsu (National Museum of Nature and Science, Tokyo, Japan) during a sampling cruise with TR/V Toyoshio-maru (Hiroshima University, Japan); mounted in Fluoromount G®.

Allotype: Adult male (RUMF-ZK-00002), collected at the same locality as the holotype; mounted in Fluoromount G®.

Paratypes: Three adult females and two adult males RUMF-ZK-00003-00007); two exoskeletons (RUMF-ZK-00008-00009) from DNA-extracted specimens (one adult female and one adult male); all collected at same locality as the holotype; all mounted in Fluoromount G®. Paratype RUMF-ZK-00003 was collected on 26 May 2013, and the others on 8 July 2013.

Additional material: Six specimens for SEM (one adult female, three adult males, and two adults gender undetermined), collected at same locality as holotype on 8 July 2013, mounted on aluminum stubs.

Sequences: 18S sequence (1778 bp) for paratype RUMF-ZK-00008, GenBank accession AB899164; 28S sequence (3292 bp) for paratype RUMF-ZK-00008, Gen Bank AB899165; COI sequence (658 bp)for paratype RUMF-ZK-00008, GenBank AB899166.

Diagnosis.

Echinoderes without acicular spines; lateroventral tubules present on segments 5 and 8, laterodorsal tubules on segment 10, and large, sieve plates on segment 9 with an inverted triangular or oval shape; females with lateral terminal accessory spines. Pectinate fringe of the sternal plate on segment 10 with short tips.

Description.

Adult with head, neck, and eleven trunk segments (Figs 2A, B, 3A, 4A). See Table 2 for measurements. Table 3 indicates the positions of cuticular structures (sensory spots, glandular cell outlets, and tubules).

Head consists of retractable mouth cone and introvert (Figs 4E, 5). Mouth cone with inner oral styles and nine outer oral styles. Exact number and arrangement of inner oral styles not examined. Each outer oral style consists of rectangular basal part and triangular distal part (Fig. 4B). Basal parts of outer oral styles alternating in size: five large in odd sectors of introvert, and four small in even sectors (Figs 4B, 5). Intro vert composed of seven rings of spinoscalids and one ring of trichoscalids (Figs 4E, 5). Ring 01 includes ten primary spinoscalids each with basal sheath and smooth long end piece (Fig. 4E). Each basal sheath with three overlapping fringes. Proximal fringe extends into three flat projections, like a trident, covering next fringe. Middle fringe with two lateral projections overlapping end piece. Distal fringe with five threads projecting between two projections of middle fringe. End piece of primary spinoscalids is longest unit. Rings 02 and 04 with 10 spinoscalids; rings 03 and 05 with 20 spinoscalids. Spinoscalids of rings 02-05 equal length. Rings 06 and 07 not examined in detail, but ring 06 with at least seven relatively short spinoscalids, and ring 07 with nine leaf-like scalids (Fig. 5). Six trichoscalids attached with trichoscalid plate in sectors 2, 4, 5, 7, 8, and 10.

Neck with 16 placids (Figs 2A, B, 4D, 5). Midventral placid broadest (ca. 18 μm at basal width and ca. 10 μm at tip width). Remaining placids similar in size, but differ alternately in tip width (ca. 12 μm at basal width and ca. 5-6 μm at tip width) (Fig. 4D).

Segment 1 consists of complete cuticular ring with thick pachycyclus at anterior margin. Bracteate cuticular hairs densely cover entire dorsal side, and posterior area of ventral side (Fig. 2A, B). Rounded subdorsal and laterodorsal sensory spots located close to anterior margin of the segment (Fig. 2A). Rounded ventrolateral sensory spots located central between anterior and posterior segment margins (Figs 2B, 4G). Type 1 glandular cell outlets situated anteriorly in middorsal and lateroventral positions (Fig. 2A, B). Posterior part of the segment with pectinate fringe showing longer fringe tips laterally (Fig. 2A, B).

Segment 2 with complete cuticular ring, like segment 1 (Fig. 2A, B). This and following eight segments with thick pachicycli at anterior margins. Bracteate cuticular hairs densely cover whole area. One oval sensory spot in middorsal position, two pairs in laterodorsal position, and one pair in ventrolateral position (Figs 2A, B, 4F, G). All sensory spots central in position. Two pairs of type 2 glandular cell outlets in both subdorsal and laterodorsal positions (Figs 2A, B, 4C, F). Pair of type 2 glandular cell outlets in lateroventral position. All type 2 glandular cell outlets of segment 2 and following six segments situated centrally of the segment. In LM observation, type 2 glandular cell outlets show funnel shaped structure, whereas in SEM observation, they show single small pore in slightly protruded cuticular surface (Fig. 4C). Posterior margin of the segment ends as pectinate fringe showing longer tips than tips of preceding segment (Figs 2A, B, 4F).

Segment 3 and following eight segments consist of one tergal and two sternal plates (Fig. 2A, B). This and following seven segments entirely covered with bracteate cuticular hairs except for anterior area (Figs 2A, B, 3B, C). Paired sensory spots in subdorsal and midlateral positions (Figs 2A, B, 4F). Type 1 glandular cell outlets of segment 3 and following seven segments situated at anterior part of segment in ventromedial position (Fig. 2B). Pair of type 2 glandular cell outlets in subdorsal and midlateral positions (Fig. 2A, B). Pectinate fringe on segment 3 and five following segments as on segment 2.

Segment 4 without sensory spots. Type 2 glandular cell outlets in subdorsal, laterodorsal, and lateroventral positions (Fig. 2A, B).

Segment 5 with lateroventral tubules (Figs 2B, 3B, 6A). Sensory spots in laterodorsal and ventromedial positions (Figs 2A, B, 3B, 6A). Paired type 2 glandular cell outlets in subdorsal position (Fig. 2A).

Segment 6 with subdorsal, laterodorsal, and ventromedial paired sensory spots (Figs 2A, B, 3B, 6A). Paired type 2 glandular cell outlets in subdorsal and midlateral positions (Figs 2A, B, 3B, 6A).

Segment 7 similar to segment 6 but with additional laterodorsal type 2 glandular cell outlets (Figs 2A, B, 3B, 6A).

Segment 8 with lateroventral tubules (Figs 2B, 3C, 6A). Paired sensory spots in subdorsal position (Fig. 2A). Positions of type 2 glandular cell outlets as on segment 7.

Segment 9 with two pairs of subdorsal sensory spots and one pair of laterodorsal and ventrolateral sensory spots (Figs 2A, B, 3C, 6B). Pair of sieve plates with wide sieve area and single posterior pore situated in midlateral position. Sieve area variable in shape, forming inverted triangle in some specimens and broad oval in others (Figs 2A, B, 3C, 6B). Tips of pectinate fringe slightly shorter in length than on preceding segment.

Segment 10 with thin laterodorsal tubules (Figs 2A, 6C). Length of laterodorsal tubules in males about twice as long as those in females. Paired subdorsal and ventrolateral sensory spots situated close to posterior margin of segment (Figs 2, 3D, 6C, D). Posterior middorsal margin elongated, extending to segment 11 in some specimens (Figs 2A, 6C), but truncate in other specimens. Posterior margin ends as pectinate fringe with short tips, except in ventrolateral area, which without pectination.

Segment 11 with lateral terminal spines (Figs 2, 3D, E, 6C, D). Short, thin lateral terminal accessory spines present only in females (Figs 2B, 3D, 6D), and three pairs of penile spines only in males (Figs 2C, 3E, 6C). Cuticular hairs absent. Paired sensory spots present in subdorsal position at base of tergal extension (Figs 2A, C, 3D, E, 6C). Ventrolateral paired sensory spots placed close to posterior margin of sternal plate (Figs 2B, D, 6D). Tergal plate projects laterally and ends in short, pointed tergal extensions (Figs 2A, C, 3D, E, 6C, D).

Etymology.

The species is named after Dr H. Komatsu (National Museum of Nature and Science, Tokyo, Japan), a taxonomist of brachyuran crabs and the first person to find Echinoderes komatsui sp. n.

Remarks.

Among congeners, Echinoderes komatsui sp. n. is most similar to Echinoderes applicitus , Echinoderes coulli , and Echinoderes marthae in sharing the following combination of characters: (1) lateral (lateroventral or lateral accessory) tubules only on segments 5 and 8, (2) middorsal spines absent on all segments, and (3) large sieve plates present ( Higgins 1977, Ostmann et al. 2012, Sørensen 2014). Echinoderes komatsui sp. n. additionally shares with Echinoderes applicitus a pair of laterodorsal tubules and a posteriorly extended margin of the tergal plate on segment 10. The latter character, previously considered diagnostic for Echinoderes applicitus , is variable in Echinoderes komatsui sp. n. Echinoderes komatsui sp. n. differs from Echinoderes applicitus in having (1) lateral terminal accessory spines in females, (2) type 2 glandular cell outlets on several segments, and (3) a pectinate fringe with short, narrow tips on the sternal plate of segment 10 (long wide tips in Echinoderes applicitus ).

Echinoderes komatsui sp. n. is identical to Echinoderes coulli in the formula of ventral tubules, and both trunk lengths overlap (304-419 μm in Echinoderes komatsui sp. n.; 248-364 μm in Echinoderes coulli ). Echinoderes komatsui sp. n. differs from Echinoderes coulli in having (1) laterodorsal tubules on segment 10, (2) lateral terminal accessory spines in females, and (3) much longer lateral terminal spines (145-164 μm and 36.6-46.9% of trunk length in Echinoderes komatsui sp. n.; 18-68 μm and 5.5-23.9% of trunk length in Echinoderes coulli ).

Echinoderes komatsui sp. n. shares with Echinoderes marthae the presence of tubules on segment 8, however, the number of tubules is different. Echinoderes komatsui sp. n. has only lateroventral tubules, whereas Echinoderes marthae has lateroventral and laterodorsal tubules. Furthermore, Echinoderes komatsui sp. n. differs from Echinoderes marthae in having (1) type 2 glandular cell outlets on some segments, (2) lateral terminal accessory spines in females, and (3) three pairs of penile spines in males (two pairs in Echinoderes marthae ).