Echinoderes undetermined
Creators: name: Grzelak, Katarzyna
name: Sørensen, Martin V.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Kinorhyncha
Cyclorhagida
Echinorhagata
Echinoderidae
Echinoderes
Echinoderes undetermined

description: Echinoderes sp. aff. E. unispinosus
Figs 36–37; Tables 26–27
Material examined
NEW ZEALAND • 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-921792. Mounted for LM in Fluoromount G on HS slide • 1 ♀, 1 ♂; same collection data as for preceding; personal reference collection of MVS. Mounted for SEM.
Distribution
Hikurangi slope, 1121 m b.s.l. See Fig. 1 for geographic location of station and Table 1 for station and specimen information.
Brief description and remarks
Echinoderes with middorsal spine on segment 4 and spines in lateroventral positions on segments 6 and 7. Glandular cell outlets type 2 present in midlateral positions on segment 1, subdorsal, laterodorsal, sublateral and ventrolateral positions on segment 2, lateral accessory positions on segment 5, and midlateral positions on segment 8. Males with three pairs of penile spines and glandular cell outlets type 2 in laterodorsal positions on segment 10; females with lateral terminal accessory spines only.
General. Adults with head, neck and eleven trunk segments. Overview of measurements and dimensions in Tables 26. Distribution of cuticular structures, i.e., sensory spots, glandular cell outlets, spines and tubes, summarized in Table 27.
Segments 1 and 2 composed of complete cuticular rings. Segment 1 with glandular cell outlets type 2 in midlateral positions, sensory spots in subdorsal and laterodorsal positions, and with glandular cell outlets type 1 in middorsal and ventrolateral positions (Figs 36B–C, 37B–C). Posterior segment margin of this and following nine segments with pectinate fringe with well-developed tips. Cuticular hairs relatively short, lightly scattered on dorsal side, and almost completely absent on lateral and ventral sides. Segment 2 with glandular cell outlets type 2 in subdorsal, laterodorsal, sublateral and ventrolateral positions (Figs 36B–C, 37B–C, E). Sensory spots present in middorsal, laterodorsal and ventromedial positions. Glandular cell outlets type 1 observed only in middorsal position. Cuticular hair covering denser on this and following eight segments (Fig. 37A–H). Segments 3 to 11 consist of one tergal and two sternal plates. Segment 3 with sensory spots in middorsal, subdorsal and midlateral positions, and glandular cell outlets type 1 in ventromedial positions. Segment 4 with short (> 20 µm) middorsal spine (Figs 36B, 37D), and glandular cell outlets type 1 located paradorsally and ventromedially; no sensory spots observed. Segment 5 without spines, but with glandular cell outlets type 2 located in lateral accessory positions (Figs 36E, 37D, G); sensory spots present in subdorsal, midlateral and ventromedial positions, and glandular cell outlet type 1 located middorsally and ventromedially. Segment 6 with spines in lateroventral positions, paradorsal, midlateral and ventromedial sensory spots and glandular cell outlets type 1 located paradorsally and ventromedially (Figs 36D–E, 37D, G–H). Segment 7 with spines in lateroventral positions, subdorsal and midlateral sensory spots, and glandular cell outlets type 1 present in middorsal and ventromedial positions (Figs 36D–E, 37G–H). Segment 8 with glandular cell outlets type 2 in midlateral positions, and sensory spots and glandular cell outlet type 1 in paradorsal and ventromedial positions (Figs 36G–H, 37H). Segment 9 without spines or glandular cell outlets type 2; sensory spots located in paradorsal, subdorsal, laterodorsal and ventrolateral positions, and glandular cell outlets type 1 present in paradorsal and ventromedial positions (Figs 36G–H, 37J–K); small sieve plate located in sublateral positions (Fig. 36H). Segment 10 with sensory spots in subdorsal and ventrolateral positions, and two glandular cell outlets type 1 located middorsally and in paraventral positions (Figs 36G–H, 37J–K). Laterodorsal glandular cell outlets type 2 present in males (Figs 36F, 37I). Segment 11 with lateral terminal spines, subdorsal sensory spots and middorsal glandular cell outlet type 1 (Fig. 36F). Cuticular hairs not present. Females with lateral terminal accessory spines, males with three pairs of penile spines (Figs 36F, H, 37I, K). Tergal extensions relatively long, sternal extensions shorter and rounded (Figs 36F, 37J–K).
Echinoderes unispinosus Yamasaki et al., 2018 is a deep-sea species, known for its wide geographic distribution. It was originally described from the deep-sea plain near Sedlo Seamount in the Northeast Atlantic at a depth of 2875 m (Yamasaki et al. 2018b), and was subsequently reported from bathyal depths (2298–3708 m depth) in the Gulf of Mexico (Alvarez-Castillo et al. 2020) and cold seep areas in the Mozambique Channel (> 700 m depth) (Cepeda et al. 2020). Moreover, very similar specimens, identified as E. cf. unispinosus, were found at several localities in the deep sea (2735–3679 m depth) off the Pacific coast of the United States (Sørensen et al. 2018).
The combination of spines and glandular cell outlets type 2 makes E. unispinosus easily distinguishable from other congeners. Echinoderes unispinosus is characterized by having only one, relatively short middorsal spine on segment 4, and lateroventral spines on segments 6 and 7, as well as glandular cell outlets type 2 on segments 1, 2, 5 and 8 and by the lack of any tubes (Yamasaki et al. 2018b). The individuals examined for the present study closely follow the morphology of this species. Morphometric data and general appearance are almost identical in New Zealand and Atlantic specimens (see Table 26 in the present contribution and Yamasaki et al. 2018: table 4). Subtle differences were noted in the sensory spot distribution though, e.g., the presence of a middorsal sensory spot on segment 3 and subdorsal ones on segment 9, observed in New Zealand specimens only, a lack of ventromedial sensory spots on segment 7 and the displacement of glandular cell outlets type 2 from sublateral to midlateral positions in our specimens (Figs 2G, 3H). However, some of these discrepancies (i.e., distribution of sensory spots on segments 3 and 9) were noted also for the Pacific specimens (Sørensen et al. 2018). The only significant difference between E. unispinosus from the type locality and specimens from the present study is the presence of laterodorsal glandular cell outlets type 2 in males that were not mentioned in the original description. These structures could potentially have been missed in the original description since Yamasaki et al. (2018b) did not have specimens available for SEM and glands in this position on segment 10 may be extremely difficult to visualize in LM. Nevertheless, the specimens found by Sørensen et al. (2018) off the US west coast also lacked these structures, indicating that the population from New Zealand might in fact represent a closely related, but yet different species. However, since our material included only three specimens and we cannot confirm whether the subtle differences observed between Atlantic and New Zealand specimens are constant within the population, we hesitate to describe a new species based on this material.
Recorded known species
description: Published as part of Grzelak, Katarzyna & Sørensen, Martin V., 2022, Echinoderes (Kinorhyncha: Cyclorhagida) from the Hikurangi Margin, New Zealand, pp. 1-108 in European Journal of Taxonomy 844 on pages 91-96, DOI: 10.5852/ejt.2022.844.1949, http://zenodo.org/record/7222155