Echinoderes blazeji, 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 : 11-18

Echinoderes blazeji sp. nov.

urn:lsid:zoobank.org:act:38F17023-13B9-487F-AF98-9F44AE186815

Figs 2–4 ; Tables 2–3

Diagnosis

Echinoderes with a very minute spine in middorsal position on segment 4 and in lateral accessory positions on segment 7. Tubes present in lateroventral positions on segment 5, sublateral positions on segment 8 and laterodorsal positions on segment 10; tubes on segment 10 well-developed in males, whereas much smaller in females. Glandular cell outlet type 2 present in midlateral positions on segment 8. Large, elongate sieve plates located midlaterally on segment 9. Lateral terminal spines twice as long in males as in females.

Etymology

The species is named after Blazej, the son of the first author – for his love of all dragons.

Material examined

Holotype

NEW ZEALAND • ♂; Pahaua Canyon, stn TAN1004/27; 41.4983° S, 175.7043° E; 1013 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NIWA-159400 . Mounted for LM in Fluoromount G on HS slide.

Paratypes

NEW ZEALAND • 1 ♀; same collection data as for holotype; NHMD-917223 • 1 ♂; same collection data as for holotype; NIWA-159401 . Mounted as holotype .

Additional material

NEW ZEALAND • 1 ♂; same collection data as for holotype; personal reference collection of MVS. Mounted for SEM • 3 ♀♀, 1 ♂; Honeycomb Canyon, stn TAN1004/58; 41.4080° S, 175.8977° E; 670 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; personal reference collection of MVS. Mounted for SEM • 1 ♂; 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 .

Description

GENERAL. Adults with head, neck and eleven trunk segments ( Figs 2–4 ). Overview of measurements and dimensions in Table 2. Distribution of cuticular structures, i.e., sensory spots, glandular cell outlets, spines and tubes, summarized in Table 3. The head morphology could not be examined in detail in any of the available specimens.

NECK. Consists of 16 placids. Midventral placid broadest, 11 µm in width and 12 µm in length, whereas all others narrower, measuring 7 µm in width at bases ( Fig. 2 ). Trichoscalid plates well developed ( Fig. 3B ).

SEGMENT 1. Consists of complete cuticular ring. Subdorsal and laterodorsal sensory spots present, situated on anterior half of segment. Sensory spots on this and following segments droplet-shaped, consisting of central pore surrounded by micropapillae ( Fig. 4C, E, G ). Glandular cell outlet type 1 not observed. Cuticular hairs arising from rounded perforation sites, distributed evenly around segment except in anterior part. Segment terminates in pectinate fringe with relatively long fringe tips ( Fig. 4C ).

SEGMENT 2. Consists of complete cuticular ring with sensory spots present in middorsal, laterodorsal, midlateral and ventromedial positions ( Figs 2A–B , 3B , 4B–C ). Glandular cell outlet type 1 present in middorsal position and as a pair in ventromedial positions. Pachycyclus of anterior segment margin of regular thickness, interrupted in middorsal position on this and following segments. Cuticular hairs densely covering entire segment. Perforation sites on this and following eight segments appear as band around segment, easily visible in LM ( Fig. 3B–C, E–I ). Posterior segment margin straight along dorsal edge, but markedly extended posteriorly in midventral position ( Fig. 4C ). Primary pectinate fringe with tips similar to those of preceding segment in middorsal to ventrolateral position and smaller and thinner tips in ventromedial and paraventral positions ( Figs 2A–B , 4B–C ).

SEGMENT 3. Present segment, and eight remaining ones, consist of one tergal and two sternal plates ( Figs 2A–B , 3A–D ). Sensory spots present in subdorsal and sublateral positions ( Fig. 3B–C ). Glandular cell outlets type 1 located in middorsal and ventromedial positions. Cuticular hairs on this and following seven segments densely covering entire segment, except for narrow area in laterodorsal position ( Fig. 2A ). Posterior segment margin straight, terminating in pectinate fringe with relatively long and uniform fringe tips along entire segment margin.

SEGMENT 4. With minute (~10 µm) middorsal spine ( Figs 3B , 4E ). Sensory spots located subdorsally ( Figs 3B , 4B ). Glandular cell outlet type 1 present in subdorsal and ventromedial positions ( Fig. 3B–C ). Segment otherwise as segment 3.

SEGMENT 5. With tubes in lateroventral positions ( Figs 2B , 3C , 4F ). Sensory spots present in subdorsal, midlateral and ventromedial positions ( Figs 2A–B , 4E–F ). Glandular cell outlets type 1 present in subdorsal and ventromedial positions. Cuticular hair covering as on preceding segment except for hairless paraventral area. Secondary fringe and posterior segment margin as on preceding segment.

SEGMENT 6. With sensory spots present in subdorsal, sublateral and ventromedial positions ( Figs 2A–B , 3E , 4E–F ). Glandular cell outlets type 1 as on preceding segment. Cuticular hair covering and secondary pectinate fringe as on segment 5.

SEGMENT 7. With minute spines (<10 µm) in lateral accessory positions ( Figs 2B , 3F , 4F ); spines hardly visible in both LM and SEM due to dense cuticular hairs covering and their inconspicuous appearance. Sensory spots located in subdorsal, midlateral, and ventromedial positions. Glandular cell outlets type 1 present in subdorsal and ventromedial positions. Segment otherwise as segment 6.

SEGMENT 8. With tubes in sublateral positions and glandular cell outlets type 2 located in midlateral positions ( Figs 2A–B , 3E–F , 4G–H ). Sensory spots present in subdorsal, laterodorsal and ventromedial positions; subdorsal pair located closer to paradorsal line than on preceding segments. Glandular cell outlets type 1 present in subdorsal and ventromedial positions. Pectinate fringe tips slightly shorter than on preceding segments.

SEGMENT 9. Without spines or tubes. Sensory spots located in subdorsal, laterodorsal, midlateral and ventrolateral positions ( Figs 2A–B , 4G ). Pair of sieve plates, composed of large, elongated sieve area located anterior to rounded areas with central pore, located in sublateral positions ( Figs 2A , 3F–I ). Glandular cell outlets type 1, cuticular hair covering and posterior segment margin as on preceding segment.

SEGMENT 10. With laterodorsal tubes, located near posterior segment margin. In males, tubes long (~15 µm) ( Figs 2A , 3H , 4I–J ). In females, tubes much shorter (~6 µm) and more flexible ( Figs 2C , 4K ), without basal part characteristic for tubes in males as well as for tubes described on segments 5 and 8. Sensory spots present in subdorsal and ventrolateral positions. Glandular cell outlets type 1 present as middorsal one, and as pair in ventromedial positions. Posterior segment margin of tergal plate straight, while margins of sternal plates concave, reaching posterior margin of terminal segment. Pectinate fringe tips significantly shorter and narrower than on preceding segment.

SEGMENT 11. With lateral terminal spines; in males, lateral terminal spines twice long as in females ( Figs 2 , 3A, D , 4A, D ; Table 2). Females with short and relatively thin lateral terminal accessory spines ( Figs 2C–D , 3I , 4K ); males with three penile spines, two of them flexible and elongated, one short and stout ( Figs 2A–B , 3H , 4I–J ).Additionally, one female specimen shows pair of fringed tubes-like structures on ventral side ( Fig. 4K ); examination of ventral side of segment 11 not possible in other specimens; therefore, we cannot conclude whether it is a sexually dimorphic character or not. Sensory spots present in subdorsal positions. Unpaired glandular cell outlet type 1 present middorsally. Segment devoid of cuticular hairs, but very short cuticular hair-like structures covering tergal extensions and posterior parts of sternal plates. Very short fringes covering margins of tergal and sternal plates. Tergal extensions elongated and triangular ( Figs 2A, C , 4J ). Sternal extensions slightly extended posteriorly, not extending beyond tergal extensions ( Fig. 2B, D ).

Distribution

Canyons: Pahaua, Honeycomb, 670–1171 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 blazeji sp. nov.

The arrangement of spines and tubes, with a minute middorsal spine on segment 4, minute lateral spines on segment 7 only and lateral tubes on segments 5 and 8, is not present in any other species of Echinoderes . These characters, combined with the large sieve plates and dense cuticular hairs, make E. blazeji sp. nov. even more distinctive and narrow the number of potential congeners down to species belonging to the so-called Echinoderes coulli -group (following the diagnosis of Yamasaki & Fujimoto 2014). Currently, this group accommodates 17 species ( Randsø et al. 2019; Yamasaki et al. 2020a; Cepeda et al. 2022; Kennedy et al. 2022) that share a number of morphological characters and habitat preferences.

Echinoderes blazeji sp. nov. can easily be distinguished from all other E. coulli -group congeners by its presence of lateral spines only on segment 7. The group is suggested to share morphological features such as absence of middorsal spines or, if present, on segment 4 only; lateral spines absent or very minute and restricted to segments 6 and 7; presence of lateral tubes on segments 5 and 8; and female lateral terminal accessory spines being either poorly-developed or absent ( Yamasaki & Fujimoto 2014). Therefore, the possession of only one pair of lateral spines makes E. blazeji unique among all other species of this group. Nevertheless, it should be stressed that these spines are extremely minute and might easily be overlooked due to the dense cuticular hair covering, especially during LM examination. But even if the presence of lateral spines on segment 7 had gone unnoticed among the nine species of the E. coulli group with a middorsal spine on segment 4 (i.e., E. annae Sørensen et al., 2016 , E. cyaneafictus Cepeda et al., 2022 , E. maxwelli ( Omer-Cooper, 1957) , E. ohtsukai Yamasaki & Kajihara, 2012 , E. parthenope Cepeda et al., 2022 , E. regina Yamasaki, 2016 , E. rex Lundbye et al., 2011 , E. serratulus Yamasaki, 2016 and E. teretis Brown, 1999 in Adrianov & Malakhov 1999), only E. annae shows the absence of lateral spines ( Omer-Cooper 1957; Adrianov & Malakhov 1999; Lundbye et al. 2011; Yamasaki & Kajihara 2012; Sørensen et al. 2016a; Yamasaki 2016; Cepeda et al. 2022). However, other conditions in E. annae make this species easily distinguishable from E. blazeji . In contrast to the new species, which has only one pair of relatively big glandular cell outlets type 2 on segment 8, E. annae possesses numbers of minute glands distributed over several segments. Moreover, the latter species is characterized by the presence of midlateral tubes on segment 9, which are absent in E. blazeji , and by very short and stout lateral terminal spines, which cannot be confused with the longer and thinner lateral spines in E. blazeji .

Furthermore, the lateral terminal spines themselves seem to represent another characteristic feature for the new species, since they are twice as long in males as in females (♂ LTS =104 µm vs ♀ LTS =50 µm, respectively). Echinoderid sexual dimorphism is usually displayed in the female presence of lateral terminal accessory spines, in the appearance of the laterodorsal tubes on segment 10 (i.e., Sørensen 2006; Pardos et al. 2016a; Grzelak & Sørensen 2018; present study) or presence of papillae/pores on the ventral side in females ( Sørensen et al. 2020). Having sexual dimorphism expressed in lateral terminal spine lengths is a rather unusual trait in Echinoderes . Differences in length of lateral terminal spines expressed as sexual dimorphism have been observed for E. aquilonius Higgins & Kristensen, 1988 and E. lusitanicus Neves et al., 2016 ( Higgins & Kristensen 1988; Neves et al. 2016), but more interestingly, also in E. coulli Higgins, 1977 – a species closely related with E. blazeji sp. nov. Higgins (1977) described two forms of females in E. coulli : one form with lateral terminal spines similar to those in males, and a second form with short lateral terminal spines being half the length of those of males. The latter shortspined form was, however, more abundant in the population and constituted about half of all examined specimens. In our case, all examined females (4 out of 9 specimens in total) had markedly shorter lateral terminal spines than males, which suggests that we might have the same kind of female dimorphism in E. blazeji . Sexual dimorphism expressed in spine lengths has also been reported for E. levanderi Karling, 1954 and the Arctic population of E. pterus Yamasaki et al., 2018 , but in these cases it was related to the length of lateroventral spines ( Karling 1954; Sørensen 2018; Yamasaki et al. 2018a).

In addition, the pattern of glandular cell outlets type 1 on the dorsal side appears to be uncommon for the new species. The taxonomic significance of the glandular cell outlet type 1 pattern, in contrast to glandular cell outlets type 2, is not yet well explored or understood. In fact, it was only quite recently that Sørensen et al. (2020) drew attention to its potential taxonomic significance. They showed that a majority of species of Echinoderes (for which we have sufficient data) show outlets on segments 4 to 9 in paradorsal or paradorsal and middorsal (depends on the segment) positions ( Sørensen et al. 2020). The presence of glandular cell outlets type 1 in subdorsal positions on segments 4 to 9, as observed for E. blazeji sp. nov., has so far only been reported from ten other, putatively closely related species, all belonging to the E. dujardinii species group, and in E. worthingi Southern, 1914 , a species also closely related to the E. dujardinii group ( Southern 1914; Sørensen et al. 2020). Since E. blazeji cannot be considered as closely related with the E. dujardinii -group, our observation of glandular cell outlets type 1 in the new species thus indicates that this morphological trait may still hide some interesting aspects.

Finally, the new species has been found in a habitat that is quite unusual for species of the E. coulli - group. The majority of these species have been recorded in intertidal marine or brackish water, with the exception of four species that inhabit subtidal, but yet shallow, marine waters ( Lundbye et al. 2011; Yamasaki 2016; Kennedy et al. 2022). In this context, E. blazeji sp. nov. is unique within the species group, since it is so far the only species inhabiting deep-sea waters.

Figures

Fig. 2. Line art illustrations of Echinoderes blazeji sp. nov. A. ♂, dorsal view. B. ♂, ventral view. C. ♀, segments 10–11, dorsal view. D. ♀, segments 10–11, ventral view. Abbreviations: see Material and methods.

Fig. 3. Light micrographs showing overviews and details of Echinoderes blazeji sp. nov. A, G–H. ♂, paratype (NIWA-159401). B–C, E–F. ♂, holotype (NIWA-159400). D, I. ♀, paratype (NHMD- 917223). A. Lateral overview of male. B. Segments 1 to 5, dorsal view. C. Segments 1 to 5, ventral view. D. Lateral overview of female. E. Segments 6 to 9, dorsal view. F. Segments 7 to 11, ventral view. G. Segments 8 to 9, lateroventral view. H. Segments 9 to 11 of male, lateral view. I. Segments 9 to 11 of female, lateral view. Abbreviations: see Material and methods.

Fig. 4. Scanning electron micrographs showing overviews and details of Echinoderes blazeji sp. nov. A. Dorsolateral overview of female. B. Segments 1 to 4, dorsolateral view. C. Segments 1 to 3, ventral view. D. Lateral overview of male. E. Segments 4 to 6, dorsal view. F. Segments 5 to 7, ventral view. G. Segments 8 to 11 of female, laterodorsal view. H. Segments 7 to 8, lateral view. I. Segments 10 to 11 of male, dorsal view. J. Segments 10 to 11 of male, dorsolateral view. K. Segments 10 to 11 of female, lateral view, with close-up of segment 11 ventral side showing ventrolateral tubules. 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.