Echinoderes joyceae, Landers, Stephen C. & Sorensen, Martin V., 2016

Landers, Stephen C. & Sorensen, Martin V., 2016, Two new species of Echinoderes (Kinorhyncha, Cyclorhagida), E. romanoi sp. n. and E. joyceae sp. n., from the Gulf of Mexico, ZooKeys 594, pp. 51-71 : 58-62

Taxon classification Animalia Echinorhagata Echinoderidae

Echinoderes joyceae sp. n. Figs 5, 6, 7

Material.

Holotype: Adult male (ZMUC KIN-845), collected from muddy sediment on October 16, 2010, at station 010-2010 (Fig. 1), at 427 m depth, about 100 km east southeast of Corpus Christi, Texas (27°09'12"N 96°09'59"W), mounted in Fluoromount G®, deposited at the Natural History Museum of Denmark. Paratypes include one female (ZMUC KIN-849), collected at same time and locality as the holotype, and three males, collected at stations 016-2010 (ZMUC KIN-850), 068-2012 (ZMUC KIN-922), and 031-2013 (ZMUC KIN-867). All paratypes were mounted in Fluoromount G® and deposited at the Natural History Museum of Denmark. Additional non-type material includes one female from station 033-2014. See Fig. 1 for localities and Table 1 for detailed station data.

Diagnosis.

Conspicuously small Echinoderes (183-209 µm) with middorsal spines on segments 4, 6 and 8, and spines in lateroventral positions on segments 6 to 9. Tubes present in ventrolateral positions on segment 2, in lateroventral positions on segment 5, and in laterodorsal positions near the posterior margin of segment 10. Glandular cell outlets type 2 present in subdorsal position on segment 2, in midlateral position on segment 6, and in sublateral position on segment 8.

Description.

Adults conspicuously small (183-209 µm in trunk length), with head, neck and eleven trunk segments (Figs 5-7). For complete overview of measures and dimensions, see Table 4. Distribution of cuticular structures, i.e., sensory spots, glandular cell outlets, spines and tubes, is summarized in Table 5.

The head (Fig. 7 A–C) consists of a retractable mouth cone and an introvert. Mouth cone with nine outer oral styles that alternate in length between slightly shorter and slightly longer ones. No outer oral styles present anterior to introvert sector 6. A fringe with three long spikes is located at the base of each outer oral style. It was only possible to obtain complete information about appearance and arrangement of scalids for introvert sectors 8 and 9. Sector 8: single central scalids of Rings 02 and 04, and paired scalds of Rings 03 and 05. No scalids present posterior to Ring 05, except for a single trichoscalid that attaches through a trichoscalid plate. Sector 9: single central scalids of Rings 02, 04, and 06, and paired scalds of Rings 03 and 05. No trichoscalids present.

The neck (Figs 5A, B, 6 A–D) has 16 placids, measuring 11 µm in length. The midventral placid is broadest, measuring 9 µm in width at its base, whereas all other are narrower, measuring 6 µm in width at their bases. The trichoscalid plates, each with a trichoscalid, present in subdorsal, laterodorsal and ventromedial positions.

Segment 1 (Figs 5A, B, 6 A–D, 7A, C, D) consists of a complete cuticular ring. Sensory spots are located in subdorsal and laterodorsal positions; sensory spots are rounded and flanked by a pair of cuticular hairs. Glandular cell outlets type 1 not present. Cuticular hairs are very scarce on the dorsal side, and not present at all on the ventral. The posterior segment margin is straight along the dorsal and lateral side, but extends more posteriorly ventrally, into a midventral point. Pectinate fringe of posterior segment margin with fringe tips alternating with small trichoid extensions.

Segment 2 (Fig. 5A, B, 6 A–D, 7A, C, D) consists of a complete cuticular ring, with tubes located in ventrolateral position. Sensory spots (with one marginal hair) located in the laterodorsal position. Pachycyclus of the anterior segment margin of regular thickness and interrupted in subdorsal and ventrolateral positions. Glandular cell outlets type 2 are located in subdorsal position. Secondary pectinate fringe not detected on this or any of the following segments. Bracteate cuticular hairs evenly distributed in a medial band around the segment. The posterior segment margin is straight and consists of a pectinate fringe, with fringe tips alternating with small trichoid extensions.

Segment 3 (Figs 5A, B, 6 A–D, 7A, D, E), and remaining segments, consisting of one tergal and two sternal plates. Pachycyclus of the anterior segment margin interrupted middorsally; thickness on the dorsal side rather average; ventral pachycycli thicker, and interrupted at the tergosternal and midsternal junctions. Sensory spots (without marginal hairs) are located in subdorsal position only. Cuticular hairs evenly distributed over tergal plate, whereas the sternal plates only have a few hairs near their anterolateral corners. Posterior segment margin and pectinate fringe as on preceding segment.

Segment 4 (Figs 5A, B, 6 A–D, 7A, D, E) with acicular spine in middorsal position, flanked by pair of paradorsal glandular cell outlets type 1. Sensory spots not present. Pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 5 (Figs 5A, B, 6 A–D, 7A, D, E) with tubes in lateroventral position. Sensory spots (without marginal hairs) present in midlateral positions. Pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 6 (Figs 5A, B, 6 A–D, 7A, D–F) with middorsal and lateroventral acicular spines. Paradorsal glandular cell outlets type 1 present anterior to middorsal spine, and paradorsal sensory spots (with or without marginal hairs) posterior to spine. One additional pair of sensory spots without marginal hairs present in ventromedial posi tion. Glandular cell outlets type 2 present in midlateral position. Pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 7 (Figs 5A, B, 6A, B, 7A, E–G, I) with acicular spines in lateroventral position, and sensory spots in paradorsal (with one marginal hair), midlateral and ventromedial positions. Pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 8 (Figs 5A, B, 6A, B, E, F, 7A, E–G, I) with middorsal and lateroventral acicular spines. Paradorsal glandular cell outlets type 1 present anterior to middorsal spine, and paradorsal sensory spots (with marginal hairs) posterior to spine. Additional glandular cell outlets type 1 are present in paraventral position, and glandular cell outlets type 2 in sublateral position. Pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 9 (Figs 5A, B, 6 A, B, E–G, 7H, I) with acicular spines in lateroventral position. Sensory spots with marginal hairs present in paradorsal and laterodorsal positions, and without marginal hairs in ventrolateral positions. Glandular cell outlets type 1 are present in paraventral position, and a pair of very minute sieve plates is located in sublateral position. Ventral pachycycli of anterior segment margin slightly thinner than those on preceding segment. Pectinate fringe of posterior margin only with regular fringe tips. Cuticular hairs as on preceding segment on tergal plate; sternal plates with cuticular hairs forming triangular patterns extending from the tergosternal junctions.

Segment 10 (Figs 5 A–D, 6 A–B, E–G, 7H, I) with laterodorsal tubes near posterior segment margin: tubes in males are well-developed, resembling regular tubes with thickened bases; tubes in females are about half as long and formed like simple tubes without thickened bases; tubes in both sexes emerge through slit-like openings in the cuticle at the posterior part of the segment. Sensory spots with marginal hair present in subdorsal positions. Glandular cell outlets type 1 not observed. Tergal plate with triangular middorsal patch of cuticular hair-like extensions, without perforation sites. Cuticular hairs with perforation sites in two patches going from the laterodorsal positions to the tergosternal junctions; hairs on the sternal plates only ventrolaterally, near the tergosternal junctions. Posterior margin of tergal plate straight; posterior margins of sternal plates concave.

Segment 11 (Fig. 5 A–D, 6 A–B, E–G, 7H, I) with lateral terminal spines. Females with thin lateral terminal accessory spines, and males with three pairs of penile spines: dorsal- and ventral-most penile spines are thin and flexible; medial ones are more stout and rigid. Sensory spots, without marginal hairs, present in paradorsal positions. Glandular cell outlets type 1 not observed. Cuticular hairs with perforation sites not present. Cuticular hair-like extensions present in patch going from the subdorsal to the middorsal areas. Tergal extensions short and pointed, with margin of inferior sides interrupted by elongated tips formed by the marginal fringes. Sternal extensions are short and broadly rounded.

Etymology.

This species is named after Joyce Wright Landers-the wife of the first author.

Remarks.

Echinoderes joyceae sp. n. is characterized by the presence of middorsal spines on segments 4, 6 and 8, ventrolateral tubes on segment 2, lateroventral tubes/ spines on segments 5 to 9, and laterodorsal tubes on segment 10. This combination of spines and tubes is not unusual among congeners, and is shared with five other species: Echinoderes bermudensis Higgins 1982, Echinoderes kristenseni Higgins 1985 Echinoderes abbreviatus Higgins 1983 Echinoderes hispanicus Pardos et al., 1998 and Echinoderes intermedius Sørensen, 2006. ( Higgins 1982, 1983, 1985; Pardos et al. 1998, Sørensen 2006). These species are distinguished from Echinoderes joyceae using a number of characteristics. All five of these species have tergal extensions on segment 11 distinct from Echinoderes joyceae . Additionally, the new species has a distinctive distribution of glandular cell outlets type 2, with locations in the subdorsal position on segment 2. Amongst the abovementioned species this is only found in Echinoderes kristenseni , which also has glandular cell outlets type 2 in lateroventral positions of segment 2, not present in Echinoderes joyceae sp. n. The most unique character combination in Echinoderes joyceae sp. n. though, is the presence of glandular cell outlets type 2 in midlateral positions of segment 6 and in sublateral positions of segment 8. This combination is not found in any other species of Echinoderes . Furthermore, Echinoderes joyceae sp. n. is characteristic by its minute size. With a trunk length ranging from 183 to 209 µm, Echinoderes joyceae sp. n. is among the smallest known Echinoderes .