Ophioplinthaca plicata ( Lyman, 1878 )

Nethupul, Hasitha, Stöhr, Sabine & Zhang, Haibin, 2022, New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach, European Journal of Taxonomy 810 (1), pp. 1-95 : 47

Ophioplinthaca plicata ( Lyman, 1878)

Figs 25–26

Ophiomitra plicata Lyman, 1878: 150 , pl. 8 figs 209–212, pl. 9 figs 233–235.

Ophioplinthaca vicina Koehler, 1904: 129-130 , pl. 25 figs 1–3.

Ophiomitra plicata – Lyman 1882: 203–204, pl. 10 figs 7–9. — Li 1987: 143–145, pl. 1 fig. 2. — Liao 2004: 139–140, fig. 70.

Ophioplinthaca plicata – O’Hara & Stöhr 2006: 84–85, fig. 8g, m–p.

Material examined

CHINA • 1 spec.; South China Sea , Zhongsha Islands, seamount; 15°36.20′ N, 113°33.74′ E; depth 1820 m; 27 Sep. 2019; collection event: stn SC014; MSV Shenhaiyongshi leg.; preserved in 95% ethanol; GenBank: MZ 198773 , MZ 203269 ; IDSSE EEB-SW0019 .

Remarks

The present study found only one specimen of O. plicata , with 12.5 mm in disc diameter ( Fig. 25 ). Within Chinese waters, this species has previously been recorded only from the South China Sea.

The arm spine articulation is well developed and placed at a slight angle to the distal edge of the lateral arm plate. A volute-shaped perforated lobe is present in most articulations, but is reduced in the dorsalmost one ( Fig. 26A–B ). The arm spine articulation has a large muscle opening and a small nerve opening ( Fig. 26A–B ), and it decreases significantly in size ventralwards ( Fig. 26A ). The vertebrae have a streptospondylous articulation, with a short, broad podial basin at the proximal end and a narrow, small distal end. The dorsal end of the vertebrae is distally triangular and proximally flattened with a longitudinal groove along the midline ( Fig. 26C–G ). The ventral end of the vertebrae has a broad ambulacral groove without an oral bridge ( Fig. 26E ).

The genus Ophioplinthaca is clearly distinguishable from other genera within the family Ophiacanthidae by the deep interradial incisions into the disc, which are lined distally by enlarged disc scales. Ophioplinthaca plicata is morphologically variable among individuals and is difficult to distinguish from other species of Ophioplinthaca , especially from O. pulchra Koehler, 1904 . The morphological features of the specimen of O. plicata from our collection and previous descriptions show complex morphological variation among individuals, and more specimens need to be analyzed from neighboring seas and the Indo-Pacific region to understand their morphological variation with respect to geographic distribution ( O’Hara & Stöhr 2006). A molecular analysis using specimens from many localities is required to understand the genetic variation in this species and its impact on morphological variation.

Distribution

480–2003 m depth. South China Sea, Philippines, Indonesia, New Caledonia, Kermadec Island, New Zealand, SE Australia ( O’Hara & Stöhr 2006; OBIS 2021).

Genus Ophiacantha Müller & Troschel, 1842

Figures

Fig. 25. Ophioplinthaca plicata (Lyman, 1878) (IDSSE EEB-SW0019). A. Dorsal disc. B. Ventral disc. C. Oral frame. D. Dorsal arm. E. Ventral arm. F. Lateral arm. G–H. Disc spine on the dorsal disc and distal end of the radial shields. Abbreviations: as = adoral shield; asa = arm spine articulation; dap = dorsal arm plate; das = dorsal arm spine; os = oral shield; tp = tentacle pore; ts = tentacle scale; vap = ventral arm plate. Scale bars: A–C = 2 mm; D–E = 1 mm; F = 500 µm; G–H = 200 µm.

Fig. 26. Ophioplinthaca plicata (Lyman, 1878), SEM (IDSSE EEB-SW0019). A–B. Lateral arm plate. C–G. Vertebrae. C. Proximal view. D. Distal view. E. Ventral view. F. Dorsal view. G. Lateral view. Abbreviations: D = dorsal; Dist = distal; dl = dorsal lobe; mo = muscle opening; no = nerve opening; Prox = proximal; V = ventral; vl = ventral lobe; vs = volute-shaped. Scale bars: A, C–D = 300 µm; B, E–G = 500 µm.