Echinoderes sp.

Grzelak, Katarzyna & Sørensen, Martin V., 2022, Echinoderes (Kinorhyncha: Cyclorhagida) from the Hikurangi Margin, New Zealand, European Journal of Taxonomy 844, pp. 1-108 : 86-91

Echinoderes sp. aff. E. lupherorum

Figs 34–35 ; Tables 24–25

Material examined

NEW ZEALAND • 1 ♂; Hikurangi Slope , stn TAN1004/4; 41.6837° S, 175.6642° E; 1046 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NIWA-159428 . Mounted for LM in Fluoromount G on glass slide • 1 ♂; Hikurangi Slope , stn TAN1004/38; 41.5937° S, 175.8532° E; 1121 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NHMD-921636 . Mounted for LM in Fluoromount G on HS slide • 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 • 2 ♂♂; Hikurangi Slope , stn TAN1004/76; 41.6833° S, 175.6500° E; 1282 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; personal reference collection of MVS. Mounted for SEM • 1 ♂; Hikurangi Slope , stn TAN1004/128; 42.0485° S, 174.7000° E; 1420 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NHMD-921635. Mounted for LM in Fluoromount G on HS slide • 1 ♂; Pahaua Canyon , stn TAN1004/22; 41.5100° S, 175.7187° E; 1188 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NIWA-159429. Mounted for LM in Fluoromount G on HS slide • 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-159430 . Mounted for LM in Fluoromount G on HS slide • 3 ♀♀, 2 ♂♂; same collection data as for preceding; 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 • 1 ♀; Campbell Canyon , stn TAN1004/126; 42.1422° S, 174.5492° E; 1495 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NHMD-921634 . Mounted for LM in Fluoromount G on HS slide • 1 ♀; Seamount 310, stn TAN1004/69; 41.3353° S, 176.1882° E; 670 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NHMD-921632 . Mounted for LM in Fluoromount G on glass slide • 1 ♂; Seamount 310, stn TAN1004/72; 41.3657° S, 176.1958° E; 985 m b.s.l.; Apr. 2010; NIWA TAN1004 Voyage; soft sediment; NHMD-921633 . Mounted for LM in Fluoromount G on glass slide • 1 ♀; same collection data as for preceding; personal reference collection of MVS. Mounted for SEM .

Distribution

Hikurangi slope, seamount, Honeycomb Canyon, Pahaua Canyon, Campbell Canyon, 670–1495 m b.s.l. See Fig. 1 for a geographic overview of stations and Table 1 for station and specimen information.

Brief description and remarks

Echinoderes with middorsal spines on segments 4 to 8, and spines in lateroventral positions on segments 6 to 9. Tubes present in lateroventral positions on segment 2 and 5, and in midlateral positions on segment 10. Minute glandular cell outlets type 2 present in subdorsal positions on segment 2, and in laterodorsal positions on segments 8 and 9. Tergal extensions of segment 11 long, constituting 6% of the trunk length. Males with three pairs of penile spines, females with lateral terminal accessory spines and papillae in ventrolateral positions on segment 7 and in ventromedial positions on segment 8.

General. Adults with head, neck and eleven trunk segments ( Figs 34–35 ). Overview of measurements and dimensions in Tables 24. Distribution of cuticular structures, i.e., sensory spots, glandular cell outlets, spines and tubes, summarized in Table 25.

Segments 1 and 2 composed of complete cuticular rings. Segment 1 with glandular cell outlets type 1 in middorsal and ventrolateral positions and sensory spots in subdorsal, laterodorsal, sublateral, and ventromedial positions ( Figs 34B , 35B–C ). Posterior segment margin of this and following nine segments with pectinate fringe with well-developed tips. Cuticular hairs relatively long, evenly distributed around segment. Segment 2 with lateroventral tubes and pair of glandular cell outlets type 2 in subdorsal positions ( Figs 34B , 35B–C ). Sensory spots present in middorsal, subdorsal, laterodorsal and ventromedial positions. Glandular cell outlets type 1 observed only in middorsal position. Cuticular hairs on this and following eight segments densely covering tergal plates and lateral halves of sternal plates; paraventral and ventromedial areas hairless ( Fig. 35A, D ). Segments 3 to 11 consists of one tergal and two sternal plates. Segments 3 with sensory spots in subdorsal positions and glandular cell outlets type 1 in middorsal and ventromedial positions. Segment 4 with middorsal spine, and sensory spots and glandular cell outlets type 1 located ventromedially. Segment 5 with middorsal spine, lateroventral tubes, sensory spots present in subdorsal and laterodorsal positions and glandular cell outlet type 1 located subdorsally and ventromedially. Segment 6 and 7 with spines in middorsal and lateroventral positions, sensory spots in paradorsal, laterodorsal and ventromedial positions, and glandular cell outlets type 1 in subdorsal and ventromedial positions ( Figs 34C–D , 35F ); females with papillae located in ventrolateral positions on segment 7 ( Figs 34E , 35E ). Segment 8 with middorsal spine, lateroventral spines, small glandular cell outlets type 2 in laterodorsal positions, sensory spots in paradorsal and laterodorsal positions and glandular cell outlets type 1 located subdorsally and ventromedially; females with papillae in ventromedial positions ( Figs 34D–E , 35E–F ). Segment 9 with lateroventral spines, small glandular cell outlets type 2 present in laterodorsal positions, four pairs of sensory spots, located in paradorsal, subdorsal, laterodorsal and ventrolateral positions, and glandular cell outlets type 1 present in subdorsal and ventromedial positions ( Figs 34D–E , 35F ); small sieve plate located in sublateral positions ( Fig. 34E ); on this and previous segment glandular cell outlets type 2 and laterodorsal sensory spots located close to midlateral line. Segment 10 with distinct, long midlateral tubes, sensory spots in subdorsal and ventrolateral positions and two glandular cell outlets type 1 located middorsally and in ventromedial positions ( Figs 34D , 35G–H ). Segment 11 with a pair of long lateral terminal spines nearly reaching trunk length ( Table 24) and subdorsal sensory spots. Cuticular hairs not present. Females with lateral terminal accessory spines, males with three pairs of penile spines. Tergal extensions long, constituting 6% of trunk length; sternal extensions shorter and rounded ( Figs 34A , 35G–H ).

Echinoderes lupherorum Sørensen et al., 2018 is one of the deep-sea species originally described from the abyssal plain off southern Oregon, in the Northeast Pacific, at a depth of 2719–3675 m ( Sørensen et al. 2018). With five additional species, i.e., E. kohni Varney et al., 2019 , E. microaperturus Sørensen et al., 2012 , E. spinifurca Sørensen et al., 2005 , E. sylviae Landers & Sørensen, 2018 and E. yamasakii Sørensen et al., 2018 , it constitutes the E. spinifurca species group, which is characterized by conspicuous, spinous tergal extensions ( Sørensen et al. 2005, 2012, 2018; Landers & Sørensen 2018; Varney et al. 2019). Additionally, the group shares other morphological features, e.g., the presence of five middorsal spines, the presence of lateroventral/ventrolateral tubes on segment 2 and midlateral tubes on segment 10, with all tubes being long and very well developed, and the presence of the female papillae on sternal plates of segments 6, 7 and/or 8. Within the group, the species are most easily distinguished by the length of their tergal extensions and the presence of glandular cell outlets type 2. Echinoderes spinifurca and E. sylviae stand out as the species without type 2 glands on segment 2 (although the latter species has glands on segments 8 and 9), while E. yamasakii is known as the species with the longest tergal extensions (see Varney et al. 2019 for details). The remaining three species, including E. lupherorum , show the greatest similarity, including an identical pattern of cuticular structures, a very similar arrangement of sensory spots and a medium length of tergal extensions ( E. microaperturus TE /TL=5%, E. lupherorum TE / TL= 7.2%, E. kohni TE /TL= 8.3%) ( Varney et al. 2019)

The individuals examined for the present study show the closest resemblance to E. lupherorum . They closely follow the morphology of E. lupherorum , including all taxonomically significant characters and all spine dimensions. Although the spines at first sight appear longer in the East Pacific specimens of E. lupherorum , the relative lengths of the spines in the specimens from New Zealand are almost identical after accounting for the difference in trunk length ( New Zealand specimens are slightly smaller with TL= 307 µm than Pacific ones with TL=371 µm) (see Sørensen et al. 2018: table 12 and Table 24 in the present study for details). The most conspicuous difference between E. lupherorum from the type locality and the specimens in the present study are the lengths of the tergal extensions, which are shorter in New Zealand individuals (TE/TL= 7.2% vs 6%, respectively). We also notice subtle differences in sensory spot distribution, which can be seen in the shift of the midlateral sensory spots present in E. lupherorum towards laterodorsal positions in our specimens, and the lack of sublateral and ventromedial sensory spots on segment 1 in the East Pacific specimens that, in contrast, are present in the latter.

We were not able to compare the glandular cell outlets type 1 distribution. In E. lupherorum from the East Pacific, the presence of this type of glands, particularly on the dorsal side, could not be confirmed due to a thin cuticle ( Sørensen et al. 2018), and a re-examination of the type material did not provide any new information. This is unfortunate as specimens from New Zealand show a rather rare pattern of glandular cell outlets type 1 on the dorsal side, namely the presence of type 1 outlets in the middorsal positions on segments 1 to 3 and the subdorsal positions on segments 4 to 9. This pattern has so far been connected with the E. dujardinii species group, and E. worthingi – a species also closely related to the E. dujardinii group ( Sørensen et al. 2020). Nevertheless, a very similar distribution pattern of dorsal glands has also been observed for E. kohni (with the exception of segment 3 glands that are present as a pair in subdorsal positions rather than as an unpaired one in middorsal position) ( Varney et al. 2019). This may indicate that species belonging to the E. spinifurca group also have an uncommon distribution pattern of glandular cell outlets type 1.

To summarize, even though we can observe some minor differences between the East Pacific and New Zealand populations of E. lupherorum , these are too minor to distinguish and describe a new species without support from molecular data. Molecular approaches appear to be increasingly necessary in taxonomic research of Echinoderes nowadays, since the differential characters appear to become increasingly more subtle the more species we examine.

Figures

Fig. 34. Light micrographs showing overview and details of Echinoderes sp. aff. E. lupherorum. A–C. ♂ (NHMD-921636). D. ♂ (NHMD-921635). E. ♀ (NHMD-921632). A. Lateroventral overview, with inset showing close-up of segment 11. B. Segments 1 to 6, dorsolateral view. C. Segments 4 to 9, dorsolateral view. D. Segments 8 to 11, dorsal view. E. Segments 6 to 9, lateroventral view. Abbreviations: see Material and methods.

Fig. 35. Scanning electron micrographs showing overviews and details of Echinoderes sp. aff. E. lupherorum. A. Ventral overview. B. Segments 1 to 5, dorsolateral view. C. Segments 1 to 3, lateroventral view. D. Laterodorsal overview. E. Segments 7 to 8, ventral view. F. Segments 5 to 9, laterodorsal view. G. Segments 10 to 11 of female, dorsal view. H. Segments 10 to 11 of female, ventral 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.