Echinoderes pterus, Yamasaki, Hiroshi, Grzelak, Katarzyna, Sorensen, Martin V., Neuhaus, Birger & George, Kai Horst, 2018

Yamasaki, Hiroshi, Grzelak, Katarzyna, Sorensen, Martin V., Neuhaus, Birger & George, Kai Horst, 2018, Echinoderespterus sp. n. showing a geographically and bathymetrically wide distribution pattern on seamounts and on the deep-sea floor in the Arctic Ocean, Atlantic Ocean, and the Mediterranean Sea (Kinorhyncha, Cyclorhagida), ZooKeys 771, pp. 15-40 : 15

Echinoderes pterus sp. n. Figs 2, 3, 4, 5, 6, 7, 8, 9; Tables 2and 3

Diagnosis.

Echinoderes with middorsal acicular spines on segments 4-8; laterodorsal tubes on segment 10; lateroventral tubes on segment 5; lateroventral acicular spines on segments 6-9; tufts of long hairs arising from slits in a laterodorsal position on segment 9; truncated tergal extensions on segment 11; without type-2 gland cell outlet.

Etymology.

The species name is derived from the Latinized Greek pterón (wing or feather), referring to the tufts of hairs on segment 9 which look like wings.

Material examined.

Holotype: Adult male (ZMB 11608), collected at station 55 in the Mediterranean deep sea off Crete (Fig. 1A, E; Table 1), mounted as a glycerol-paraffin slide on a Cobb aluminum frame.

Paratypes: Adults, collected in the Mediterranean Sea off Crete; four males and one female, collected at station 24 (ZMB 11609-11613); one female, collected at station 51 (ZMB 11614); one female, collected at station 52 (ZMB 11615); one male, collected at station 56 (ZMB 11616); one male and three females, collected at station 62 (ZMB 11617-11620); one female, collected at station 64 (ZMB 11621); one male, collected at station 65 (ZMB 11622); one male, collected at station 66 (ZMB 11623); one male, collected at station 94 (ZMB 11624); four males and seven females, collected at station 1167.1 (ZMB 11628-11638); one male and one female, collected at station 1169.1 (ZMB 11639-11640); one female, collected at station 918 (ZMB 11625); one male and one female, collected at station 930 (ZMB 11626-11627); (Fig. 1A, E, F; Table 1). All paratypes mounted as glycerol-paraffin slides on Cobb aluminum frames.

Additional material for LM: all adults; seven males and 12 females, collected at station 152 on Karasik Seamount, mounted as glycerol-paraffin slides on Cobb aluminum frames (ZMB 11642-11660); one male and one female, collected at station 31 north of Svalbard, mounted in Fluoromount G (NHMD-202798 and NHMD-202799); one male and one female, collected at station 43 north of Svalbard, mounted in Fluoromount G (NHMD-202800 and NHMD-202801); one male, collected at station 717 on the Sedlo Seamount, mounted as a glycerol-paraffin slide on a glass slide (ZMB 11641) (Fig. 1 A–D; Table 1).

Additional material for SEM: adults, mounted on aluminum stubs; five males and nine females, collected at station 63 (ZMB 11664 a–d, 11665 a–d, 11666a, 11667 a–d, 11668a), Mediterranean deep sea off Crete; five males and four females, collected at station 66, Mediterranean deep sea off Crete (ZMB 11661 a–c, d, 11662 a–c, 11663a, c); one male and four females, collected at station 152, the Karasik Seamount (ZMB 11669a, b, 11670b, d, 11671e) (Fig. 1A, B, E; Table 1).

Type locality.

Deep-sea trench off Crete, Mediterranean Sea, (34°30'19"N, 26°11'30"E), 4,332 m depth (Fig. 1A, E; Table 1).

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, gland cell outlets, spines, tubes, and sieve plates).

Head consisting of retractable mouth cone and introvert (Fig. 3B). Mouth cone with three rings of inner oral styles and nine outer oral styles (Figs 3C, 5). Pharyngeal crown shown anterior to inner oral styles in specimens with artificially protruded head (Fig. 3B), but located interior and posterior of inner oral styles in nature. Five thin and tube-like inner oral styles in ring 03, five thick spinose inner oral styles in ring 02, and ten spinose inner oral styles in ring 01. Two spinose structures present at basal part of ring -01 inner oral styles between sectors 2 and 3, 4 and 5, 7 and 8, and 9 and 10 (Figs 3C, 5). Each outer oral style consisting of rectangular basal part and triangular distal part, with basal part alternating in size between five larger ones in odd sectors and four smaller ones in even sectors (Figs 3B, C, 5). Each outer oral style with six long spinose processes bifurcated at their tips. One pair of additional short spinose processes originating slightly more anteriorly and laterally on either side of each outer oral style. Introvert composed of one ring of primary scalids, five rings of spinoscalids, and one ring of trichoscalids (Figs 3B, D, 5). Each primary spinoscalid consisting of basal sheath and distal end piece. Basal sheath with two layers of proximal fringes. End piece long, covered with minute hairs proximally, bluntly ending at distal tip. Each spinoscalid of rings 02-05 composed of basal sheath with fringed edge and distal long-spinose end piece. Spinoscalids in rings 02 and 03 longer than those in rings 04 and 05. Thin hair-like structures present at basal part of each spinoscalid. Trichoscalids arising from trichoscalid plates. Each trichoscalid covered with long hairs.

Neck with 16 placids (Figs 2A, B, 4B, C). Midventral placid broadest (Fig. 4C). Remaining placids similar in size. Two trichoscalid plates present ventrally and four dorsally, each associated with ventromedial, subdorsal, and laterodorsal placid, respectively (Fig. 4B, C).

Segment 1 consisting of complete cuticular ring. Sensory spots located in subdorsal and laterodorsal position (Figs 2A, 4D, 6A, B). Few hairs flanking each sensory spot. Two type-1 gland cell outlets present in tandem in middorsal and additional single pair in lateroventral position (Figs 2A, B, 4D, 6A, C). Posterior part of this and following ten segments with primary pectinate fringe (Figs 2A, B, 4D, 6A, C). Pectinate fringe teeth of primary pectinate fringe thin and long. Segment devoid of cuticular hairs except for hairs associated with sensory spots (Figs 3A, 6A, C).

Segment 2 with complete cuticular ring as segment 1. This and following eight segments with thick pachycyclus at anterior margin of each segment (Figs 2A, B, 4A, D–F). Pachycyclus interrupted middorsally in segments 3-9 as well as at tergosternal and midsternal junctions in segments 3-10. Cuticular hairs rising from perforation sites in anterior and central area of this and following eight segments (Fig. 6A); hairs long, rather thin and flexible, and tending to curl up (Figs 6D, 7C). Sensory spots present in middorsal, laterodorsal and ventromedial position (Figs 2A, B, 6A, C). Type-1 gland cell outlets present in middorsal and ventromedial position.

Segment 3 and following eight segments consisting of one tergal and two sternal plates (Fig. 2A, B). No sensory spots present. Type-1 gland cell outlets situated in middorsal and ventromedial position.

Segment 4 with middorsal acicular spine (Figs 2A, 4D, D, 6A). No sensory spots present. Type-1 gland cell outlets present in paradorsal and ventromedial position.

Segment 5 with middorsal acicular spine and lateroventral tubes (Figs 2A, B, 4 D–F, 6D). Lateroventral tubes consisting of relatively thick and short basal part and long flexible distal part. Sensory spots absent. Type-1 gland cell outlets present in paradorsal and ventromedial position (Fig. 4F).

Segment 6 with middorsal and lateroventral acicular spines (Figs 2A, B, 4E, F, 6 D–F, 7A, B). Sensory spots present in paradorsal, midlateral, and ventromedial position (Figs 2A, B, 6 D–F, 7A, B). Type-1 gland cell outlets present paradorsally and ventromedially (Fig. 4F).

Segment 7 with middorsal and lateroventral acicular spines (Figs 2A, B, 4E, 6E, 7A, B, 8A). Sensory spots present in ventromedial position in specimens from Mediterranean deep sea off Crete and those from the Anaximenes Seamount (Fig. 6E). Sensory spots absent in specimens from the Karasik Seamount, north of Svalbard, and the Sedlo Seamount (Fig. 6F). Type-1 gland cell outlets present paradorsally and ventromedially.

Segment 8 with middorsal and lateroventral acicular spines (Figs 2A, B, E, 7 A–C, 9 A–D). Sensory spots present paradorsally (Fig. 7A, C). Type-1 gland cell outlets present in paradorsal and ventromedial position.

Segment 9 with lateroventral acicular spines (Figs 2B, D, E, 4A, 7B, C, 8 B–D, 9A). Lateroventral acicular spines in male specimens from the Karasik Seamount, north of Svalbard, and the Sedlo Seamount conspicuously thick and long (Figs 2E, 8C), whereas thickness of spines similar to those on preceding segments in other specimens (Figs 2B, D, 4A, 7B, C, 8B, D, 9A). Tufts of hairs arising from slits in laterodorsal position (Figs 2A, C, 7 B–D, 8A). Most hairs of the tufts conspicuously longer than other usual cuticular hairs. Laterodorsal and ventrolateral sensory spots present (Figs 7B, C, 8C, 9A). Type-1 gland cell outlets present in paradorsal and ventromedial position. Small rounded sieve plates present in sublateral position.

Segment 10 with laterodorsal tubes (Figs 2A, C, 7C, 9B). Subdorsal and ventrolateral sensory spots present (Figs 7C, 8C, 9A). Two type-1 gland cell outlets aligned middorsally. Additional pair of type-1 gland cell outlets present in ventromedial position.

Segment 11 with lateral terminal spines (Figs 2 A–D, 4A, 7C, 8 B–D). Three pairs of penile spines present in males, with two pairs being tube-like and one pair thick and cone shaped (Figs 2A, E, 8C, 9A, B). One pair of lateral terminal accessory spines present in females (Figs 2C, D, 7C, 8D). Subdorsal sensory spots present. Two type-1 gland cell outlets present middorsally. Tergal extensions very short and truncate; sternal extensions triangular, extending slightly beyond tergal ones (Figs 2 A–D, 4A, 8B, D, 9A, B).