Ophientrema scolopendrica ( Lyman, 1883 )

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 : 39-44

Ophientrema scolopendrica ( Lyman, 1883)

Figs 20–22

Ophiacantha scolopendrica Lyman, 1883: 259 .

Ophiacantha leucosticta H.L. Clark, 1911: 235 .

Ophientrema leucosticta – Matsumoto 1917: 111.

Ophientrema leucostictum – H.L. Clark 1911: 217. — Koehler 1922a: 85, pl. 8 figs 1–4, pl. 94 fig. 1.

Material examined

CHINA • 1 spec.; South China Sea , E of Hainan Island, seamount; 18°30.14′ N, 112°49.62′ E; depth 1400 m; 28 Jun. 2019; collection event: stn SC003; MSV Shenhaiyongshi leg.; preserved in -80°C; IDSSE EEB-SW0035 • 1 spec.; South China Sea , SE of Hainan Island, seamount; 17°27.00′ N, 111°15.00′ E; depth 1550 m; 24 Mar. 2018; collection event: stn SC018; MSV Shenhaiyongshi leg.; preserved in -80°C; GenBank: MZ198775 , MZ203271 ; IDSSE EEB-SW0021 • 2 specs; same collection data as for preceding; IDSSE EEB-SW0036 , IDSSE EEB-SW0037 • 2 specs; South China Sea , SE of Hainan Island, seamount; 17°35.80′ N, 111°02.00′ E; depth 1750 m; 3 Apr. 2018; collection event: stn SC022; MSV Shenhaiyongshi leg.; preserved in -80°C; IDSSE EEB-SW0038 , IDSSE EEB-SW0039 • 1 spec.; South China Sea , SE of Hainan Island, seamount; 17°17.81′ N, 110°31.92′ E; depth 1460 m; 4 Apr. 2018; collection event: stn SC023; MSV Shenhaiyongshi leg.; preserved in -80°C; IDSSE EEB- SW0040 • 1 spec.; South China Sea , Xisha Islands, seamount; 17°06.00′ N, 110°58.20′ E; depth 1500 m; 23 Mar. 2018; collection event: stn SC017; MSV Shenhaiyongshi leg.; preserved in -80°C; GenBank: MZ198774 , MZ203270 ; IDSSE EEB-SW0020 • 1 spec.; same collection data as for preceding; IDSSE EEB-SW0041 .

Description ( IDSSE EEB-SW 0020)

MEASUREMENTS. Disc diameter 13 mm, length of arms 80–100 mm.

DiSC. Disc slightly pentagonal ( Fig. 20A–B ). Dorsal disc covered by thin, uncalcified, dark skin with surface of small projecting granules ( Fig. 20A ). Ventral disc smooth, with few or no smooth granules ( Fig. 20B, E ). Radial shields short, distally wider and widely separated ( Fig. 21F ). Distal half of radial shields uncovered, bearing few granules on outer margin but do not reach periphery of disc ( Fig. 21F–G ). Oral shields short, twice as wide as long and somewhat rhombic. Adoral shields short and wide, proximally meeting fully or some hardly meeting ( Fig. 21A ). Teeth significantly larger than oral papillae. Lateral oral papillae broad, flat, rounded, transparent, distal edges break easily ( Fig. 21E ). Number of lateral oral papillae varies among jaws, three per side, but some jaws have four oral papillae on one side ( Fig. 21E ). Genital slits conspicuous and extending from distal end of oral shield to periphery of disc ( Fig. 21B ).

ARMS. Dorsal arm plate transversely oval with pointy corners, nearly twice as broad as long, covering only about half width of arm ( Fig. 21C ). First ventral arm plate transverse diamond-shaped, with rounded angles, next two plates square with convex outer margin. Beyond third ventral arm plate, arm segments nearly semicircular with slight peak, covering one third of width of arm segment ( Fig. 21D–E ). Tentacle scale absent on first arm segment and starts to appear from second or third arm segment ( Fig. 21E ). Lateral arm plates stout, forming well defined spine ridge and meeting on ventral side except on first two arm segments ( Fig. 21D–F ). Seven arm spines on an elevated ridge, four dorsal and three to four ventral. Dorsal arm spines often nearly two segments long, stout, nearly cylindrical and tapering to a blunt point ( Fig. 21G ). Ventral arm spines smaller, thorny with hook-shaped tip, with a few spiny points on their adoral or proximal side ( Fig. 21H–I ). Ventralmost arm spines on first few arm segments elongated and less hook-like, with rough surface but distalwards along arm developing into a short, little hyaline hook ( Fig. 21I ).

COLOR. Dark olivaceous green on dorsal disc, light brown color on radial shield, dorsal arm spine, and dorsal and ventral arm plate; dark reddish brown on oral papillae and ventral arm spine ( Fig. 20A–B ).

OSSiCLE MORPHOLOGY.Ventralmost arm spine short, thorny, with proximally oriented tip ( Fig. 22A ). Arm spine articulation well developed, with volute-shaped perforated lobe except in dorsal- and ventralmost articulations ( Fig. 22B–C ), with large muscle opening and small nerve opening ( Fig. 22B–C ). Vertebrae with short zygospondylous articulation with a broad dorsal extension of lateral muscle flanges, distally abruptly truncated, dorsal median furrow moderately expressed, and podial basins short and large ( Fig. 22D–G ). Middle segment of ventral vertebrae with deeply expressed furrow without oral bridge ( Fig. 22F ).

Remarks

The genus Ophientrema includes only two species, O. euphylactea (H.L. Clark, 1911) and O. scolopendrica ( Lyman 1883) . H.L. Clark (1911) mentioned a band of black spots on the dorsal disc of O. scolopendrica caused by tissue on the inner surface of the skin. In the present study, we examined nine specimens and all of them concurred with the description of the holotype of O. scolopendrica . However, there are some slightly different features in the color of the dorsal disc and number of lateral oral papillae, but the color of the present specimens matched the description by Koehler (1922a).

Among the specimens from this study, we identified two different color patterns: 1) dark olivaceous green on the dorsal disc, light brown on radial shield, dorsal arm spine, and dorsal and ventral arm plate; 2) dark reddish brown on oral papillae and ventral arm spine, dark olivaceous green and brown on dorsal disc and bright red pink on radial shield, light brown on oral papillae, dorsal and ventral arm plate, and arm spine ( Fig. 20A–D ). Some specimens possessed seven oral papillae on one jaw, but when we examined our specimens and previous records, we considered this as intraspecific variation. Ophientrema euphylactea is distinguished from O. scolopendrica by the scale density on the dorsal disc and by having spiniform oral papillae (H.L. Clark 1911).

Distribution

1000–2000 m depth. South China Sea, Eastern Japan, Indonesia (Gulf of Tomoni), Eastern China Sea, Tasman Sea, Madagascar ( OBIS 2021).

Genus Ophiurothamnus Matsumoto, 1917

Figures

Fig. 20. Ophientrema scolopendrica (Lyman, 1883) (A–B, E–G = IDSSE EEB-SW0020; C–D = IDSSE EEB-SW0021). A, C. Dorsal disc. B, D. Ventral disc. E. Center of dorsal disc. F. Lateral disc. G. Granules on the disc. Abbreviation: rs = radial shield. Scale bars: A–D = 2 mm; E = 1 mm; F–G = 500 µm. (F and G taken of well-dried specimen)

Fig. 21. Ophientrema scolopendrica (Lyman, 1883) (IDSSE EEB-SW0020). A. Oral frame. B. Lateral disc. C. Dorsal arm. D–E. Ventral arm.F. Lateral arm.G. Dorsal arm spine. H–I. Ventralmost arm spines on the arm. Abbreviations: as = adoral shield; dap = dorsal arm plate; das = dorsal arm spine; gs = genital slit; os = oral shield; vap = ventral arm plate. Scale bars:A–B, E–F = 500 µm; C–D = 1 mm; G–I = 200 µm. (A–B, E–H taken after thoroughly drying the specimen)

Fig. 22. Ophientrema scolopendrica (Lyman, 1883), SEM (IDSSE EEB-SW0020). A. Ventral arm spine. B–C. Lateral arm plate. D–G. Vertebrae. D. Proximal view. E. Distal view. F. Ventral view. G. Dorsal 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 = 200 µm; B = 300 µm; C–G = 500 µm.