Chen W et al. (2021), Description of three species of ophioplinthacid...

ECB-ART-49079

PeerJ 2021 Apr 06;9:e11566. doi: 10.7717/peerj.11566.

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Description of three species of ophioplinthacids, including a new species, from a deep seamount in the Northwest Pacific Ocean.

Chen W , Na J , Zhang D .

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Five specimens of brittle star were collected from a deep-sea seamount in the Northwest Pacific, and identified into three species. One which is new to science, Ophioplinthaca grandisquama n. sp., can be easily distinguished from its congeners by the distinctly elongated and stout tentacle scales, stout and long disc spines, capitate with typically elongate to flaring head bearing numerous distinct thorns, radial shields roughly triangular and contiguous distally. One specimen was identified as Ophioplinthaca semele (Clark, 1949), which had been reported in Hawaii seamounts, is a new record of this species in the Northwest Pacific. The remaining specimen was an unknown species of Ophioplinthaca, with some different characteristics from other species of Ophioplinthaca. However, we, herein, prefer not to attach a name to this specimen until more morphological characteristics are available. The finding of this new species and two new records further enriches the distribution of Ophioplinthaca in the seamount of Northwest Pacific, providing useful information for marine protection in the cobalt-rich area.

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	Figure 1. Map of the study seamount (indicated by the small red block) in the northwest Pacific (A) and sampling sites of specimens of ophioplinthacids (B).Credit attribution: Dr. Lin Shiquan.
	Figure 2. In situ and on board photos of Ophioplinthaca grandisquama n. sp.(A) In situ observations, several specimens attached on a Primnoid (Calyptrophora sp.). (B–D) Photos on board. (B) Holotype (RSIO56060). (C) Paratype (RSIO56014). (D) Paratype (RSIO56013).
	Figure 3. Morphological characters of Ophioplinthaca grandisquama n. sp. (Holotype: RSIO56060).(A) Dorsal view of disc. (B) Enlarged disc spines. (C) Ventral view of disc. (D) Dorsal view of arm, proximal part. (E) Ventral view of arm, proximal part. Abbreviations: AD, adoral plate; AS, arm spine; DAP, dorsal arm plate; DP, dental papillae; DS, disc spine; GS, genital slits; J, jaw; OP, lateral oral papilla; OS, oral shield; RS, radial shield; VAP, ventral arm plate; TE, tentacle; TS, tentacle scale. Scale bars: one mm.
	Figure 4. Morphological characters of Ophioplinthaca grandisquama n. sp. (Paratype: RSIO56013, RSIO56014).(A–B) Morphological characters of paratype RSIO56014. (A) Dorsal view of disc. (B) Ventral view of disc. (C–D) Morphological characters of paratype RSIO56013. (C) Dorsal view of disc. (D) Ventral view of disc. Abbreviations: AD, adoral plate; AS, arm spine; DAP, dorsal arm plate; DP, dental papillae; DS, disc spine; GS, genital slits; J, jaw; OP, lateral oral papilla; OS, oral shield; RS, radial shield; VAP, ventral arm plate; TE, tentacle; TS, tentacle scale. Scale bars: two mm.
	Figure 5. SEM photographs of skeletons of Ophioplinthaca grandisquama n. sp. (Paratype: RSIO56014).(A) Disc spine. (B) Ventral arm plate from proximal segment, external view. (C) Dorsal arm plate from proximal segment, external view. (D) Ventral-most arm spine. (E) Dorsal-most arm spine. (F) Oral plate, abradial face. (G) Oral plate, adradial face, white arrows point to oral papillae sockets and pores. (H) Dental plate. (I) Adradial genital plate. (J) Abradial genital plate. (K) Adradial genital plate, distal end. (L) Radial shield, external aspect. (M) Radial shield, internal aspect. (N–R) Vertebrae from proximal portion of arm. (N) Distal view. (O) Proximal view. (P) Lateral view. (Q) Dorsal view. (R) Ventral view. (S) External view of LAP. (T) Internal view of LAP. Abbreviations: AG, aboral groove; DL, dorsal lobe; dors, dorsal; dist, distal; DW, presumable depression for water ring canal; FB, foot basin; GC, adradial genital plate condyle; k, knob; LAC, lateral ambulacral canal; LR, lateral ridge of the adradial genital plate, attachment area of the abradial genital plate; MO, muscle opening; NO, nerve opening; p, perforations; PD, podial basins; prox, proximal; r, ridge; RC, radial shield condyle; TN, tentacle notch; vent, ventral; VL, ventral lobe; WVC, water vascular canal; Z, zagapophyses. Scale bars: 200 µm.
	Figure 6. In situ (A) and on board (B) photos of Ophioplinthaca semele.
	Figure 7. Morphological characters of Ophioplinthaca semele (RSIO56057).(A) Dorsal view of disc. (B) Radial shields. (C) Disc spines. (D) Ventral view of disc. (E) Dorsal view of arm, Proximal part. (F) Ventral view of arm, proximal part. Abbreviations: AD, adoral plate; AS, arm spine; DAP, dorsal arm plate; DP, dental papillae; DS, disc spine; GS, genital slits; J, jaw; OP, lateral oral papilla; OS, oral shield; RS, radial shield; VAP, ventral arm plate; TE, tentacle; TS, tentacle scale. Scale bars: one mm (B, C), two mm (A, D–F).
	Figure 8. SEM photographs of Ophioplinthaca semele (RSIO56057).(A) Disc spine. (B) Dorsal arm plate from proximal segment, External view. (C) Ventral arm plate from proximal segment, external view. (D–H) Vertebrae from proximal portion of arm. (D) distal view. (E) Dorsal view. (F) Ventral view. (G) Proximal view. (H) Lateral view. (I) External view of lateral arm plate. (J) Internal view of lateral arm plate. Abbreviations: AG, aboral groove; DL, dorsal lobe; dors, dorsal; dist, distal; LAC, lateral ambulacral canal; MO, muscle opening; NO, nerve opening; P, perforations; PD, podial basins; prox, proximal; R, ridge; TN, tentacle notch; vent, ventral; VL, ventral lobe; WVC, water vascular canal; Z, zagapophyses. Scale bars: 200 µm.
	Figure 9. In situ (A) and on board (B) photos of Ophioplinthaca sp.
	Figure 10. Morphological characters of Ophioplinthaca sp. (RSIO56058).(A) Dorsal view of disc. (B) Disc spines. (C) Ventral view of disc. (D) Dorsal view of arm, proximal part. (E) Ventral view of arm, proximal part. Abbreviations: AD, adoral plate; DP, dental papillae; AS, arm spine; DAP, dorsal arm plate; DS, disc spine; GS, genital slits; J, jaw; OP, lateral oral papilla; OS, oral shield; OTS, oral tentacle scale; RS, radial shield; VAP, ventral arm plate; TE, tentacle; TS, tentacle scale. Scale bars: two mm (A, C–E), 0.2 mm (B).
	Figure 11. SEM photographs of Ophioplinthaca sp. (RSIO56058).(A) Disc spine. (B) Dorsal arm plate from proximal segment, external view. (C) Ventral arm plate from proximal segment, external view. (D–H) Vertebrae from proximal portion of arm. (D) proximal view. (E) Dorsal view. (F) Ventral view. (G) Distal view. (H) Lateral view. (I) External view of lateral arm plate. (J) Internal view of lateral arm plate. Abbreviations: AG, aboral groove; DL, dorsal lobe; dors, dorsal; dist, distal; LAC, lateral ambulacral canal; MO, muscle opening; NO, nerve opening; P, perforations; PD, podial basins; prox, proximal; R, ridge; TN, tentacle notch; vent, ventral; VL, ventral lobe; WVC, water vascular canal; Z, zagapophyses. Scale bars: 200 µm.
	Figure 12. Lateral arm plates of four species of Ophioplinthaca from the proximal to distal segments of the arm, all shown with ventral edges upwards (in order to compare with existing research, refer to the layout format of Numberger-Thuy & Thuy (2020).(A–C) Ophioplinthaca grandisquama n. sp., (A) Proximal arm segments, (B) Middle arm segments, (C), distal arm segments; (D–F) Ophioplinthaca semele, (D) proximal arm segments, (E) middle arm segments, (F), distal arm segments; (G–I) Ophioplinthaca sp., (G) proximal arm segments, (H) middle arm segments, (I), distal arm segments; (J–L) Ophioplinthaca defensor, (J) proximal arm segments, (K) middle arm segments, (L), distal arm segments. The vertebral articular structures marked in red, like an undivided digit 1 with a broad, nose-shaped beak. Abbreviations: be, beak; rrs, right root serif.
	Figure 13. Maximum likelihood tree of the genus Ophioplinthaca based on COI sequences.Colored bars in red refer to MOTUs in ABGD.

References [+] :

Boissin, DNA barcoding of reef brittle stars (Ophiuroidea, Echinodermata) from the southwestern Indian Ocean evolutionary hot spot of biodiversity. 2017, Pubmed, Echinobase