Dracoderes snufkini Yamasaki, 2015, sp. nov.

Dracoderes snufkini sp. nov.

[New Japanese name: Ryukyu tatsutogekawa] (Figs 2–5; Tables 3, 4)

Dracoderes sp. 1. Sørensen et al. 2012: 228 –229, fig. 11.

Material examined. Holotype: Adult female (ZIHU-04984), collected 25 January 2014 at station 1 (Fig. 1), mounted in Fluoromount G®. Allotype: Adult male (ZIHU-04985), station 1, mounted in Fluoromount G®. Paratypes: One adult female and one adult male (ZIHU-04986–04987), two adult females and one adult male (RUMF-ZK-00019–00021), one adult female and two adult males (ZMUC KIN- 000834–000836), all from station 1, all mounted in Fluoromount G®. Additional material: Two male exoskeletons (ZIHU-04988–04989) from specimens for DNA extraction, collected 17 July 2013, station 2 (Fig. 1), mounted in Fluoromount G®. Three males, three females, and two sex-undetermined specimens for SEM, station 1, 25 January 2014, mounted on aluminum stubs stored in the author’s laboratory (University of the Ryukyus, Okinawa, Japan). Sequences: 18S (1594 bp) from ZIHU-04989, GenBank accession number LC 032113; 28S (3249 bp) from ZIHU-04989, LC 032114; COI (629–658 bp) from ZIHU-04988–04989 and one specimen for which exoskeleton was lost, LC 032115 – LC 032117.

Type locality. Oura Bay, Okinawa, Japan (26°31.863' N, 128°3.179' E).

Diagnosis. Dracoderes with lateroventral tubules on segments 2 and 5; thick and plump middorsal spines on segments 2 and 9; thick and plump paradorsal spines on segments 3–8, alternately laterally displaced; ventral primary pectinate fringe on segment 1 with long, wide, and conspicuous tips.

Etymology. The specific epithet snufkini is after the Diving Team Snack Snufkin, which advertises the beauty, greatness, and importance of nature in Oura Bay, Okinawa, the type locality of the new species. ‘Snufkin’ is also the nickname for Mr Nishihira, a delegate on the team. The team also cooperated with the 1st Umisawa Kai (Field workshop for young marine biologists) held in Oura Bay from 24–28 January 2014, and helped collecting the new species.

Of the Japanese name, ‘Ryukyu’ is from the Ryukyu Islands where the species was found, and ‘tatsutogekawa’ is from the Japanese name for the genus Dracoderes proposed in Murakami (2005).

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

Head consists of retractable mouth cone and introvert. Mouth cone with inner oral styles and outer oral styles. Introvert with spinoscalids and at least nine trichoscalids. Exact number and arrangement of inner oral styles, outer oral styles, and spinoscalids not determined.

Neck with four dorsal and five ventral placids (Figs 2 A, B, 3B, E, 4B, C, E). Midventral and midlateral placids slightly wider than others. Ventral placids close together, dorsal placids at intervals occupied by cuticular folding (Figs 2 A, B, 3B, E, 4B). Surface of placids anteriorly covered with fine hairs, surface of posterior part smooth, lacking any cuticular structures (Fig. 4 B).

Trunk with 11 segments; segment 1 consists of complete cuticular ring; segments 2–11 consist of one tergal and two sternal plates (Figs 2 A, B, 3A). Thickened cuticle forms pachycyclus at anterior margin of all segments (Figs 2 A, B, 3A–E). Middorsal acicular spines on segments 2 and 9 (Figs 2 A, C, 3D, E, 4F, 5B). Paradorsal acicular spines on segments 3–8, laterally displaced alternately right and left (Figs 2 A, C, 3D, E, 4F, 5A, B). All dorsal spines short, plump and pointed. Funnel-shaped subcuticular structures visible at base of each dorsal acicular spine under LM observation (Figs 2 A, C, 3D, E). Pair of lateral accessory tubules on segment 8, difficult to find under LM but visible with SEM (Fig. 5 B–D). Pair of lateroventral tubules on segments 2 and 5 (Figs 2 B, 3B, C, 4C, 5A). Pair of lateroventral acicular spines on segments 6–9 (Figs 2 B, D, 3C, 5A–E). All sensory spots rounded, with collar of papillae around single central pore (Fig. 4 D). Cuticular hairs on posterior part of segment 1, tergal plates of segments 2–9, and posterior part of sternal plate of segments 2–9 (Figs 2 A, B, 4C, E–G, 5A–E). No secondary pectinate fringe or glandular cells were observed.

Segment 1 shows conspicuous primary pectinate fringe with long, wide spinous processes on ventral side (Figs 2 B, 3B, 4C, G), each spinous process observable by both LM and SEM. Dorsal to lateral primary pectinate fringe with short, densely arranged tips, difficult to identify individually with LM (Figs 2 A, B, 3E, 4E, G). Pair of sensory spots subdorsally, laterodorsally, and midlaterally; two pairs of sensory spots ventromedially (Figs 2 A, B, 3B, E, 4C, E–G).

Segment 2 with middorsal acicular spine and lateroventral tubules (Figs 2 A, B, 3B, E, 4C, F). Pairs of sensory spots in ventrolateral and ventromedial positions (Figs 2 B, 3B). Two pairs of sensory spots in laterodorsal position (Figs 2 A, 3E, 4F, G). Primary pectinate fringe with short, densely arranged tips ventromedially to midventrally. Middorsal and lateroventral parts of fringe show long, thin tips and area of short, densely arranged tips, respectively (Fig. 4 G).

Segment 3 with paradorsal acicular spine located to the left or to the right (Figs 2 A, 3D, E, 4F). Perispinal paradorsal sensory spots present (Figs 2 A, 3D, E). Additional sensory spots present in laterodorsal, midlateral and ventrolateral positions (Figs 2 A, B, 3B, E, 4F, G). Primary pectinate fringe of sternal plates with short, densely arranged tips. Fringe of tergal plate similar to that of preceding segment (Fig. 4 G).

Segment 4 with paradorsal acicular spine, on the opposite side of that on the preceding segment (Figs 2 A, 3D, E, 4F). Perispinal paradorsal sensory spots present (Figs 2 A, 3D, E). Additional sensory spots in laterodorsal, ventrolateral, and ventromedial positions (Figs 2 A, B, 3B, E, 4F). Primary pectinate fringe similar to than the fringe on the preceding segment.

Segment 5 similar to segment 3, except for presence of lateroventral tubules (Figs 2 B, 3C, 4F, 5A).

Segment 6 with paradorsal acicular spine and lateroventral acicular spines (Figs 2 A, B, 3C, D, 5A). Perispinal subdorsal sensory spots present (Figs 2 A, 3D). Additional sensory spots in laterodorsal, midlateral, ventrolateral, and ventromedial positions (Figs 2 A, B, 5A). Primary pectinate fringe on this and following four segments with short, densely arranged tips on tergal and sternal plates.

Segment 7 similar to segment 6 except for absence of sensory spots in ventromedial position (Fig. 5 A–C).

Segment 8 similar to segment 6 except for the presence of lateral accessary tubules, difficult to identify with LM, but visible with SEM (Fig. 5 B–D).

Segment 9 with middorsal acicular spine and lateroventral acicular spines (Figs 2 A–D, 3C, D, G, 5B–E). Sensory spots in subdorsal, laterodorsal, midlateral, ventrolateral, and ventromedial positions (Figs 2 A–D, 3C, D, 5B–D). Nephridial pores small, posteriorly directed opening with a few papillae in lateral accessory position (Fig. 5 D).

Segment 10 lacking acicular spine and tubule. Sensory spots in subdorsal, laterodorsal, and ventrolateral positions (Figs 2 A–D, 3C, G, 5E).

Segment 11 with lateral terminal spines (Figs 2 A–D, 3A, C, F, G, 4A, 5E). Lateral terminal accessory spines lacking in both sexes. Females with slit-like gonopore openings in lateroventral position (Fig. 3 G). Males with three pairs of penile spines (Fig. 2 D, 3F, 5E). Two pairs of sensory spots subdorsally; one in central part of segment, another at tip of tergal extension (Fig. 2 A, C). Additional sensory spots in ventrolateral position (Figs 2 B, D, 3G, 5E). Primary pectinate fringe with short, densely arranged tips laterally and ventrally (Fig. 5 E). Posterior end with triangular tergal extension dorsally. Ventral side of tergal extension covered densely with minute hairs (Fig. 5 E).

Remarks. Dracoderes snufkini sp. nov. differs markedly from congeners in the shape of the primary pectinate fringe on the ventral side of segment 1; it has a primary pectinate fringe strongly developed, i.e., the tips of the pectination are conspicuously long and wide on the ventral side on segment 1, whereas in congeners the primary pectinate fringe on segment 1 consists of relatively narrow, short inconspicuous tips (Higgins & Shirayama 1990; Adrianov & Malakhov 1999; Sørensen et al. 2012; Thomsen et al. 2013). Dracoderes snufkini also differs from congeners (except D. orientalis) in lacking lateroventral tubules on segment 10, and from D. orientalis in having lateroventral tubules on segments 2 and 5 (Adrianov & Malakhov 1999).

Dracoderes snufkini is very similar to Dracoderes sp. 1 in Sørensen et al. (2012). Similarities include 1) the same numbers and positions of spines and tubules, 2) short, plump dorsal spines, 3) similar width/length of trunk, trunk segments and spines (Table 3), and 4) a strongly developed primary pectinate fringe on the ventral side on segment 1. Sørensen et al. (2012) described Dracoderes sp. 1 as having a strongly developed primary pectinate fringe on segment 2, but this character was not found by me in his specimens. I assume the posterior margin of segment 1 was mistaken as the posterior margin of segment 2 (Sørensen et al. 2012: Fig. 11C). In addition, Dracoderes sp. 1 was found at Kabira Bay, Ishigaki Island, Okinawa, very close to one of the localities where D. snufkini was collected (Fig. 1). These morphological and geographic similarities indicate that specimens referred to as Dracoderes sp. 1 in Sørensen et al. (2012) are conspecific with D. snufkini.