Echinoderes legolasi, Grzelak & Sørensen, 2022

Grzelak, Katarzyna & Sørensen, Martin V., 2022, Echinoderes (Kinorhyncha: Cyclorhagida) from the Hikurangi Margin, New Zealand, European Journal of Taxonomy 844, pp. 1-108 : 60-66

Echinoderes legolasi sp. nov.

urn:lsid:zoobank.org:act:5FE9F89C-A48F-42E8-9E97-491D7A88CFB9

Figs 23–25 ; Tables 16–17

Diagnosis

Echinoderes with spines in middorsal position on segments 4, 6 and 8, and spines in lateroventral positions on segments 6 to 9. Tubes present in lateroventral positions on segment 5 and laterodorsal positions on segment 10. Glandular cell outlets type 2 in sublateral positions on segment 1, subdorsal, laterodorsal, sublateral and ventrolateral positions on segment 2 and midlateral positions on segment 8. A protuberance-like structure emerges between segments 10 and 11 in middorsal position.

Etymology

The species name refers to Legolas – Elf of Mirkwood, one of the characters in J.R.R. Tolkien’s “ The Lord of the Rings ”. Legolas was an excellent archer, and another very valuable member of the Fellowship of the Ring.

Material examined

Holotype

NEW ZEALAND • ♂; Seamount 310 , stn TAN1004/72; 41.3657° S, 176.1958° E; 985 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NIWA-159422 . Mounted for LM in Fluoromount G on HS slide.

Additional material

NEW ZEALAND • 1 ♂; Hikurangi Slope , stn TAN1004/44; 41.5258° S, 175.8003° E; 728 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; personal reference collection of MVS. Mounted for SEM .

Description

GENERAL. Adults with head, neck and eleven trunk segments ( Figs 23–25 ). Overview of measurements and dimensions in Table 16. Distribution of cuticular structures, i.e., sensory spots, glandular cell outlets, spines and tubes, summarized in Table 17. No details regarding scalid arrangement and morphology could be provided, because introvert of specimen mounted for SEM was partially retracted.

NECK. With 16 placids. Midventral placid broadest, 9 µm in width and 11 µm in length, whereas all others narrower, measuring 6 µm in width at bases and 11 µm in length, similar in size ( Figs 24C , 25D ). Trichoscalid plates well developed.

SEGMENT 1. Consists of complete cuticular ring. Pair of glandular cell outlets type 2 present in sublateral positions ( Figs 23B , 24C , 25B ). Sensory spots located medially on segment, in subdorsal and laterodorsal positions ( Figs 23A , 24B , 25B ); sensory spots on this and following segments relatively large, with tuft of micropapillae surrounding central pore. Glandular cell outlet type 1 present in middorsal, and ventrolateral positions ( Figs 23A–B , 24B–C ). Cuticular hairs relatively long,arranged in single transverse row medially on segment. Posterior segment margin almost straight, forming pectinate fringe. Fringe with well-developed long and flexible tips, homogenous along segment margin ( Fig. 25B ).

SEGMENT 2. Consists of complete cuticular ring. Glandular cell outlets type 2 present in subdorsal, laterodorsal, sublateral and ventrolateral positions ( Figs 23A–B , 24B–C , 25B ). Sensory spots located in laterodorsal and ventromedial positions ( Figs 23A–B , 25B ). Glandular cell outlets type 1 present in middorsal and ventromedial positions. Pachycyclus of anterior segment margin of regular thickness, without interruption. Secondary pectinate fringe present near anterior segment margin of this and following segments ( Fig. 25E, G ). Cuticular hairs evenly distributed over dorsal part of segment, ventral areas less hairy; cuticular hairs shorter and thinner on anterior part of segment. Posterior segment margin almost straight; pectinate fringe tips as on preceding segment.

SEGMENT 3. Present segment, and eight remaining ones, consist of one tergal and two sternal plates ( Figs 23A–B , 24C, E–F , 25D ). Pachycyclus of anterior segment margin slightly thinner than on preceding segment, interrupted at tergosternal and midsternal junctions and middorsally, on this and following seven segments. Segment with sensory spots located in subdorsal and midlateral positions ( Figs 24B– C , 25B ), and glandular cell outlets type 1 in middorsal and ventromedial positions. Cuticular hairs distributed across tergal plate as on preceding segment; ventromedial and paraventral areas on this and following seven segments with thinner and much shorter, non-bracteate hairs. Posterior segment margin straight, terminating in pectinate fringe with fringe tips slightly shorter, as on preceding segments, but still long and flexible.

SEGMENT 4. With spine in middorsal position ( Figs 23A , 24B ). Sensory spots not present. Pair of glandular cell outlet type 1 present in paradorsal and ventromedial positions. Pachycycli, pectinate fringe and cuticular hairs as on preceding segment.

SEGMENT 5. With tubes in lateroventral positions ( Figs 23B , 24C, E ). Sensory spots located midlaterally. Glandular cell outlets type 1 present in middorsal and ventromedial positions. Segment otherwise as segment 4.

SEGMENT 6. With spines in middorsal and lateroventral positions ( Figs 23A–B , 24D–E , 25D–F ). Sensory spots present in paradorsal, midlateral and ventromedial positions ( Figs 23A–B , 25C ). Glandular cell outlets type 1 present in paradorsal and ventromedial positions ( Figs 23A–B , 24D–E ). Tips of pectinate fringe of posterior segment margin as on preceding segments. Segment otherwise as segment 5.

SEGMENT 7. With spines in lateroventral positions ( Figs 23B , 24E ). Sensory spots present in paradorsal, midlateral and ventromedial positions ( Figs 23A–B , 25C, E–F ), and glandular cell outlets type 1 in middorsal and ventromedial positions ( Figs 23A–B , 24E ). Cuticular hair covering as on preceding segment. Pectinate fringe of posterior segment margin with slightly narrower and shorter tips.

SEGMENT 8. With spines in middorsal and lateroventral positions ( Figs 23A–B , 24G , 25E ), and glandular cell outlets type 2 in midlateral positions ( Figs 23A , 24E, G , 25C ). Sensory spots present in subdorsal positions, but located close to paradorsal line ( Fig. 25E ). Glandular cell outlets type 1 in paradorsal and ventromedial positions. Pectinate fringe of posterior segment margin as on preceding segment.

SEGMENT 9. With spines in lateroventral positions ( Figs 23B , 25D ). Sensory spots located in subdorsal, midlateral and ventrolateral positions; subdorsal pair situated close to paradorsal area ( Figs 23A–B , 24G , 25E, G ). Glandular cell outlets type 1 present in paradorsal and ventromedial positions. Small, rounded sieve plates in lateral accessory positions ( Fig. 25C ). Pectinate fringe as on preceding segment. Cuticular hairs shorter, but cuticular hair covering similar to as on preceding segment, except middorsal and paradorsal areas covered with very short and thin non-bracteate hairs ( Fig. 25G ) similar to ones present on lateral halves of sternal plates, posteriorly expanding into subdorsal areas.

SEGMENT 10. With laterodorsal tubes located near posterior segment margin ( Figs 23A , 24G , 25G–H ). Sensory spots present in subdorsal and ventrolateral positions ( Figs 24G , 25G–H ). Glandular cell outlets type 1 present as one middorsal and pair of ventromedial ones. Cuticular hairs scarcer than on preceding segment. Central part of tergal plate covered with short and thin non-bracteate hairs as on preceding segment ( Fig. 25G–H ). Posterior segment margin of tergal plate straight, with much shorter fringe and narrower tips than those on preceding segment ( Fig. 25G–H ); margins of sternal plates extend midventrally ( Fig. 23B ).

SEGMENT 11. With pair of lateral terminal spines ( Fig. 23C ). Males with three pairs of penile spines; dorsal and ventral penile spines thin and flexible tubes, whereas median ones markedly thicker, conical and stout ( Figs 23A , 24H , 25G–H ). Female condition unknown. Sensory spots present in paradorsal and subdorsal positions; subdorsal pair located near posterior margin of tergal extensions ( Figs 23A , 25H ). Middorsal protuberance-like structure extends from intersegmentary joint ( Figs 23A , 25G ). Segment devoid of cuticular hairs, but with dense covering of short hair-like extensions in dorsal areas of tergal plates. Short fringes covering margins of tergal and sternal plates. Tergal extensions short, sternal extensions do not extend beyond tergal extensions ( Figs 23A–B , 24H , 25G ).

Distribution

Hikurangi slope and Seamount 310, 728– 985 m b.s.l. See Fig. 1 for a geographic overview of stations and Table 1 for station and specimen information.

Taxonomic remarks on Echinoderes legolasi sp. nov.

Echinoderes legolasi sp. nov. is one of 34 species (including E. frodoi sp. nov., E. samwisei sp. nov., E. leduci sp. nov., and E. aragorni sp. nov.) having middorsal spines on segments 4, 6 and 8, but can easily be distinguished from all other congeners by its unique patterns of spines, tubes and glandular cell outlets type 2. The most exclusive feature of E. legolasi is the presence of four pairs of glandular cell outlets type 2 on segment 2. This character is shared only with one other species, i.e., E. anniae described by Sørensen et al. (2018) from the United States west coast. Except for the identical pattern of cuticular structures on segment 2, both species also share the presence of glandular cell outlets type 2 in midlateral/sublateral positions on segments 1 and 8. However, E. anniae can be discriminated from E. legolasi by its tube pattern, lacking the lateroventral tubes on segment 5. Instead, E. anniae has glandular cell outlets type 2 in this position ( Sørensen et al. 2018). Furthermore, E. legolasi possesses short tergal extensions, which differ considerably from the relatively long and narrow tergal extensions present in E. anniae , and significantly shorter lateral terminal spines in relation to the trunk length (LTS/ TL= 51% in E. legolasi vs 99% in E. anniae ).

The new species shows most resemblance to Echinoderes hamiltonorum Sørensen et al., 2018 . Echinoderes hamiltonorum is also described from deep waters (> 3000 m deep) off the United States west coast ( Sørensen et al. 2018). The two species have almost identical arrangements of cuticular structures, a highly similar trunk appearance, and they share the shape of the tergal extensions, the presence of a protuberance protruding from the intersegmental joint between segments 10 and 11, and an even length and shape of the pectinate fringes. The main difference between the two species is the possession of either tubes or glandular cell outlets type 2 in ventrolateral positions on segment 2. Both species have subdorsal, laterodorsal and sublateral glands on segment 2, but in ventrolateral positions E. hamiltonorum has tubes instead of glandular cell outlets type 2 as in E. legolasi sp. nov. Both structures (glands vs tubes) are easily distinguishable in SEM, but the ventrolateral tubes in E. hamiltonorum are hard to visualize in LM ( Sørensen et al. 2018). The attachment point of the tubes might resemble the margins of the outlets, which might potentially be a source of confusion during the identification process. Therefore, the easiest way to distinguish the species would be through SEM examination. However, even without access to SEM information, it should be possible to distinguish E. legolasi and E. hamiltonorum by the location of type 2 glands on segment 8 and some morphometric details. Echinoderes legolasi has glandular cell outlets type 2 in midlateral positions on segment 8, whereas these structures are displaced to sublateral positions in E. hamiltonorum ( Sørensen et al. 2018) . Furthermore, the new species has a shorter trunk (175 µm vs 233 µm) and has a proportionally longer middorsal spine on segment 8. In E. hamiltonorum , the middorsal spines on segments 6 and 8 are comparable in length (74 µm vs 75 µm, respectively), while the spine on segment 6 is noticeably shorter than the one on segment 8 in E. legolasi (51 µm vs 65 µm, respectively).

Hence, in summary, E. legolasi sp. nov. and E. hamiltonorum can be distinguished by the presence of ventrolateral glands type 2 on segment 2 and sublateral glands type 2 on segment 8 in E. legolasi , and in the general combination of spine and glandular cell outlet type 2 patterns.

Figures

Fig. 23. Line art illustrations of Echinoderes legolasi sp. nov. A. ♂, dorsal view. B. ♂, ventral view. Abbreviations: see Material and methods.

Fig. 24. Light micrographs showing overview and details of Echinoderes legolasi sp. nov., ♂, holotype (NIWA-159422). A. Dorsal overview. B. Segments 1 to 6, dorsal view. C. Segments 1 to 6, ventral view. D. Segments 5 to 8, dorsal view. E. Segments 5 to 8, ventral view. F. Ventral overview. G. Segments 8 to 11, dorsal view. H. Segments 10 to 11, ventral view. Abbreviations: see Material and methods.

Fig. 25. Scanning electron micrographs showing overviews and details of Echinoderes legolasi sp. nov. A. Lateral overview. B. Segments 1 to 4, dorsolateral view. C. Segments 6 to 9, lateral view. D. Ventral overview. E. Segments 6 to 10, dorsal view. F. Segments 5 to 7, dorsal view. G. Segments 8 to 11, dorsal view. H. Segments 10 to 11, dorsal view. Abbreviations: see Material and methods.

Fig. 1. Map showing the sampling stations. Colour codes indicate slopes (red), canyons (green), and seamounts (yellow). Inset shows New Zealand with a frame marking the sampling area.