Echinoderes gandalfi, 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 : 38-45

Echinoderes gandalfi sp. nov.

urn:lsid:zoobank.org:act:84D3AEAA-391B-4C5C-81FC-380B198251F2

Figs 14–16 ; Tables 10–11

Diagnosis

Echinoderes with spines in middorsal position on segments 6 and 8, and spines in lateroventral positions on segments 6 to 9. Tubes present in ventrolateral positions on segment 2, lateroventral positions on segment 5, lateral accessory positions on segment 8, and laterodorsal positions on segments 9 and 10. A protuberance-like structure emerges between segments 10 and 11 in middorsal position. Lateral terminal spines long, always exceeding trunk length.

Etymology

The species name refers to Gandalf the Grey, one of the main characters in the novel “ The Fellowship of the Ring ”, the first volume of J.R.R. Tolkien’s “ The Lord of the Rings ”. He helped form the Fellowship of the Ring to destroy the One Ring.

Material examined

Holotype

NEW ZEALAND • ♂; Pahaua Canyon , stn TAN1004/31; 41.4962° S, 175.6828° E; 730 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NIWA-159407 . Mounted for LM in Fluoromount G on HS slide.

Paratypes

NEW ZEALAND • 2 ♀♀; same collection data as for holotype; ♀ NHMD-916356 , ♀ NIWA-159408 . Mounted as holotype • 1 ♀; Pahaua Canyon, stn TAN1004/12; 41.5508° S, 175.7250° E; 1350 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NIWA-159409 . Mounted as holotype • 1 ♀, 1 ♂; Pahaua Canyon , stn TAN1004/22; 41.5100° S, 175.7187° E; 1188 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; ♀ NHMD-916362 , ♂ NIWA-159410 . Mounted as holotype • 1 ♂; Pahaua Canyon , stn TAN1004/27; 41.4983° S, 175.7043° E; 1013 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; ♂ NIWA-159411 . Mounted as holotype • 1 ♀, 2 ♂♂; Honeycomb Canyon, stn TAN1004/58; 41.4080° S, 175.8987° E; 670 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; ♀ NIWA-159412 , ♂♂ NHMD-916357–916358 . Mounted as holotype • 1 ♀, 3 ♂♂; Campbell Canyon, stn TAN1004/126; 42.1422° S, 174.5492° E; 1495 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; ♀ NHMD-916360 , 1 ♂ NIWA-159413 , 2 ♂♂ NHMD-916359 and 916361. Mounted as holotype .

Additional material

NEW ZEALAND • 5 ♀♀, 3 ♂♂; Pahaua Canyon , stn TAN1004/27; 41.4983° S, 175.7043° E; 1013 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; personal reference collection of MVS. Mounted for SEM • 1 ♀, 2 ♂♂; Honeycomb Canyon , stn TAN1004/62; 41.4760° S, 175.9477° E; 1171 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; personal reference collection of MVS. Mounted for SEM • 1 ♀; Campbell Canyon , stn TAN1004/126; 42.1422° S, 174.5492° E; 1495 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 14–16 ). Overview of measurements and dimensions in Table 10. Distribution of cuticular structures, i.e., sensory spots, glandular cell outlets, spines and tubes, summarized in Table 11. No details regarding scalid arrangement and morphology could be provided, because introverts of all specimens mounted for SEM fully or partially retracted.

NECK. With 16 placids. Midventral placid broadest, 8 µm in width and 15 µm in length, whereas all others narrower, measuring 6 µm in width at their bases and 13 µm in length, similar in size ( Fig. 15B– C ). The trichoscalid plates are well-developed ( Fig. 15B–C ).

SEGMENT 1. Consists of complete cuticular ring. Sensory spots located on anterior half of segment, in subdorsal positions. Glandular cell outlet type 1 present in middorsal and ventrolateral positions ( Figs 14A–B , 15B–C ). Cuticular hairs relatively long, distributed around segment. Posterior segment margin almost straight, forming pectinate fringe with very short, sawtooth-like fringe tips.

SEGMENT 2. Consists of complete cuticular ring, with tubes located in ventrolateral positions ( Figs 14A– B , 15C , 16C ). Sensory spots present in middorsal, laterodorsal and ventromedial positions; sensory spots on this and following eight segments relatively large, with numerous micropapillae surrounding central pore and long marginal hair, giving them droplet-shaped appearance ( Fig. 16B ). Glandular cell outlets type 1 present in middorsal and ventromedial positions ( Figs 14A–B , 15B ). Pachycyclus of anterior segment margin of regular thickness, without interruption. Secondary pectinate fringe present near anterior segment margin of this and following segments, but usually covered by preceding segment. Fairly long cuticular hairs evenly distributed across tergal plate; paraventral areas on this and following three segments with thinner and much shorter, non-bracteate hairs, emerging through perforation sites visible in SEM only. Posterior segment margin almost straight, but with rounded midventral extension; pectinate fringe tips as on preceding segment.

SEGMENT 3. Present segment, and eight remaining ones, consist of one tergal and two sternal plates ( Figs 14A–B , 15A–C , 16B–C ). Pachycyclus of anterior segment margin of medium thickness, interrupted at tergosternal and midsternal junctions and middorsally, on this and following seven segments. Segment with middorsal and ventromedial glandular cell outlets type 1; no sensory spots or other traits observed. Cuticular hairs interrupted by hairless midlateral area, otherwise as on preceding segment. Posterior segment margin straight, terminating in pectinate fringe with longer and more slender fringe tips than on preceding segments.

SEGMENT 4. With glandular cell outlets type 1 present in paradorsal and ventromedial positions. Segment otherwise as segment 3.

SEGMENT 5. With tubes in lateroventral positions ( Figs 14B , 15C , 16A–B ). Sensory spots present in midlateral and ventromedial positions; the latter, however, missing in some specimens examined under SEM ( Fig. 16B ) and for some specimens (including holotype) examined under LM presence/absence of ventromedial sensory spots could not be confirmed. Glandular cell outlets type 1 present in paradorsal and ventromedial positions. Pectinate fringe of posterior segment margin and cuticular hairs as on preceding segment.

SEGMENT 6. With spines in middorsal and lateroventral positions ( Figs 14A–B , 15C–D , 16A–B, D–F ). Sensory spots present in paradorsal, midlateral and ventromedial positions ( Fig. 14A–B ). Glandular cell outlets type 1 present in paradorsal and ventromedial positions ( Figs 14A–B , 15C ). Tips of pectinate fringe of posterior segment margin slightly longer than on preceding segments. Segment otherwise as segment 5.

SEGMENT 7. With spines in lateroventral positions, and sensory spots in paradorsal, midlateral and ventromedial positions ( Figs 14A–B , 15C–D , 16B ). Glandular cell outlets type 1 present in ventromedial positions, not observed on the dorsal side. Cuticular hairs covering as on preceding segment except for hairless paraventral and ventromedial areas, on this and following four segments.

SEGMENT 8. With spines in middorsal and lateroventral positions, and tubes in lateral accessory positions ( Figs 14A–B , 15C–D , 16D, F ). Sensory spots present in paradorsal positions only. Glandular cell outlets type 1 as on preceding segment. Pectinate fringe of posterior segment margin and cuticular hairs as on preceding segment.

SEGMENT 9. With spines in lateroventral positions and long (~18 µm) tubes in laterodorsal positions ( Figs 14A–B , 15D , 16D–F ). Sensory spots located in paradorsal, subdorsal and ventrolateral positions ( Figs 14A–B , 15B–C , 16F ). Glandular cell outlets type 1 present in paradorsal and ventromedial positions. Small, rounded sieve plates located in lateral accessory positions. Cuticular hairs covering as on preceding segment, but less dense on dorsal side around sensory spots and tubes. Pectinate fringe of posterior segment margin with tips slightly shorter than on preceding segments.

SEGMENT 10. With laterodorsal tubes located near posterior segment margin; tubes well developed in both sexes ( Figs 15E–F , 16G–H ). Sensory spots present in ventrolateral positions. Glandular cell outlets type 1 present as two middorsal ones, and in ventromedial positions. Cuticular hairs significantly scarcer than on preceding segment. Central part of tergal palate devoid of hairs; short cuticular hairs lightly scattered on lateral halves only. Hairs on sternal plates short and present mostly on lateral halves and near posterior segment margin. Posterior segment margin of tergal plate straight, with shorter fringe tips than those on preceding segment; margins of sternal plates with longer fringe tips than those on tergal plate and extend midventrally, almost reaching posterior margin of terminal segment.

SEGMENT 11. With very long lateral terminal spines, always exceeding trunk length ( Fig. 14C ; Table 10). Males with three pairs of penile spines; dorsal and ventral ones are long, relatively thin tubes, whereas median ones markedly thicker, conical and stout ( Figs 14A–B , 16H ). Females with lateral terminal accessory spines ( Fig. 14D–E ). Sensory spots present in paradorsal positions ( Figs 14A, D , 16D ); sensory spots smaller than on preceding segments, without long marginal hairs. Glandular cell outlets type 1 present in subdorsal positions. Middorsal protuberance-like structure extends from intersegmentary joint ( Figs 14A,D , 15E–F , 16G ). Segment devoid of cuticular hairs, but with short cuticular hair-like structures covering paradorsal area and short fringes covering margins of tergal and sternal plates. Tergal extensions short and pointed, with small tooth at inner margin ( Fig. 15G ). Sternal extensions broadly rounded, not extending beyond tergal extensions.

Distribution

Canyons: Pahaua, Campbell, Honeycomb, 730–1495 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 gandalfi sp. nov.

The spine pattern with middorsal spines on segments 6 and 8 is rare among species of Echinoderes , and is shared with only three species, i.e., E. daenerysae , E. hviidarum Sørensen et al., 2018 and E. ultraabyssalis Adrianov & Maiorova, 2019 , and an undescribed species, Echinoderes sp. 1 , from the Atacama Trench ( Grzelak & Sørensen 2018; Sørensen et al. 2018; Adrianov & Maiorova 2019; Grzelak et al. 2021). Furthermore, E. gandalfi sp. nov. possesses laterodorsal tubes on segment 9, which is another relatively rare trait, shared with all the abovementioned species, which suggests that these species might represent a group of closely related species. The only other species with tubes in this position on the dorsal side of segment 9 is E. belenae (see Pardos et al. 2016b) and E. frodoi sp. nov., E. dalzottoi sp. nov. and E. leduci sp. nov., all described in the present study. Nevertheless, none of these species can in any way be confused with E. gandalfi due to their significantly different spine patterns.

Echinoderes gandalfi sp. nov. probably shows most resemblance to E. ultraabyssalis , the deepest kinorhynch species described so far (> 9000 m water depth) from the Kuril-Kamchatka Trench, and Echinoderes sp. 1 , found in the Atacama Trench at a water depth of 7700 m ( Adrianov & Maiorova 2019; Grzelak et al. 2021). Echinoderes gandalfi shares several features with these hadal/deep-sea trench species, including the presence of tubes in ventrolateral positions on segment 2, lateroventral positions on segment 5, and in lateral accessory positions on segment 8, the presence of a middorsal protuberance between segments 10 and 11, as well as very long lateral terminal spines, the shape of the tergal extensions and the lack of glandular cell outlets type 2. Nevertheless, despite the overall similarity, E. gandalfi can be distinguished from both congeners by its morphometrics. Echinoderes gandalfi is markedly smaller in trunk length than both species (TL: 186 µm vs 267 µm and 257 µm, respectively) but has proportionally longer lateral terminal spines, which always exceed the trunk length, resulting in a markedly higher LTS/TL ratio in E. gandalfi in comparison with E. ultraabyssalis and Echinoderes sp. 1 (LTS/TL: 132% vs 59% and 91%, respectively) ( Adrianov & Maiorova 2019; Grzelak et al. 2021). It appears that also the arrangement and number of sensory spots show some differences. Unique for E. gandalfi is the presence of laterodorsal sensory spots on segment 2 but the lack of these structures in ventrolateral positions on segment 1, and in middorsal position on segment 10 as found in the other two species. In addition, E. ultraabyssalis lacks well-developed laterodorsal tubes on segment 10, which are present in both sexes and easy to visualize even with LM in E. gandalfi .

Figures

Fig. 14. Line art illustrations of Echinoderes gandalfi sp. nov. A. ♂, dorsal view. B. ♂, ventral view. C. ♂, segments 10 to 11, with lateral terminal spines drawn in full length, dorsal view. D. ♀, segments 10 to 11, dorsal view. E. ♀, segments 10 to 11, ventral view. Abbreviations: see Material and methods.

Fig. 15. Light micrographs showing overview and details of Echinoderes gandalfi sp. nov. A–D, F. ♂, holotype (NIWA-159407). E, G. ♀, paratype (NHMD-916362). A. Ventral overview. B. Segments 1 to 6, dorsal view. C. Segments 1 to 9, ventral view. D. Segments 6 to 10, dorsal view. E. Segments 10 to 11 of female, dorsal view. F. Segments 10 to 11 of male, dorsal view. G. Segment 11 of female, ventral view. Abbreviations: see Material and methods.

Fig. 16. Scanning electron micrographs showing overviews and details of Echinoderes gandalfi sp. nov. A. Lateral overview. B. Ventral overview. C. Segments 1 to 4, ventral view. D. Lateral overview. E. Segments 4 to 10, dorsal view. F. Segments 8 to 9, lateral view. G. Segments 10 to 11 of female, dorsal view. H. Segments 10 to 11 of male, 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.