Ophiarachnella septemspinosa ( Müller & Troschel, 1842 )

Parameswaran, Usha V., Nowshad, B. Mohammed, Dixit, Sudhanshu, Manjebrayakath, Hashim, Idreesbabu, K. K. & Saravanane, N., 2020, New records of brittle stars (Echinodermata: Ophiuroidea) from the Lakshadweep atolls, northern Indian Ocean, with notes on Indophioderma ganapatii Sastry Marimuthu & Rajan, 2019, Zootaxa 4809 (3), pp. 560-570 : 564-565

Ophiarachnella septemspinosa ( Müller & Troschel, 1842)

( Fig. 4 a-f)

Ophiarachna septemspinosa Müller & Troschel, 1842: 105–106 .

Pectinura septemspinosa — Lütken 1869: 15.— Lyman 1882: 17.— Döderlein 1888: 830–831, pl. 32(4a–c).— de Loriol 1893: 395–397, pl. 13(2).— Koehler 1905: 9.

Pectinura rigida Lyman, 1874: 224 .

Ophiarachna armata Troschel, 1879: 137–138 .

Ophiarachnella septemspinosa —H. L. Clark 1909: 126; 1938: 349–350; 1946: 263–264.— Koehler 1930: 273.— Cherbonnier & Guille 1978: 218–219, pl. 16(1–2).— Guille & Vadon 1985: 64.— Marsh et al. 1993: 62.— Olbers et al. 2015: 110–111, fig. 9(A–B).— Boissin et al. 2016: 288–289, fig. 5(e).

Material examined: Agatti Island—western reef (10° 51.97’ N, 72° 12.42’ E, 20m), coll. S. Dixit on 06.11.2018 by SCUBA diving, 1 specimen ( CMLRE IO /SS/ECD/00235) .

Description: D.d. 36 mm, disc pentagonal, arms 7–8 times d.d. Disc covered uniformly with rounded granules, on dorsal and ventral side, leaving only small, dark, circular radial shields bare ( Fig 4 a-c). Oral shield large, spear- head shaped, longer than broad; supplementary oral shields small, broadly oval, some bare; adoral shields small, triangular, not contiguous; oral plates covered by granules ( Fig. 4d ). Teeth broadly rounded; 1–2 large, rounded, scale like tooth papillae, followed by three scale-like oral papillae—corresponding with infradental papilla, secondary adoral shield spine and adoral shield spine; Lyman’s ossicle projecting between the latter and the first ventral arm plate ( Fig. 4d ). Genital slits long, reaching edge of the disc ( Fig. 4d ). Dorsal arm plates rectangular, faintly carinate, over twice as wide as long, distal edge distinctly scalloped ( Fig. 4 b-c). Ventral arm plates with concave inner and convex outer margins ( Fig. 4 d-e). Arm spines increasing from two to nine in the basal segments; spines adpressed, flat and pointed; spines as long as segment, except the ventral-most which is twice as long, distinctly flattened with squared-off tips ( Fig. 4 e-f). Two rounded leaf-like tentacle scales basally, becoming one distally ( Fig. 4e ).

Colour: In life, uniformly greyish-green with dark green radial shields; preserved specimen dull grey with dark brownish-grey radial shields.

Distribution: Saudi Arabia, Kenya, South Africa, Madagascar, Reunion, Mauritius, Maldives, Sri Lanka, Indonesia, Christmas Island, Papua New Guinea, Australia, New Caledonia, Fiji, Philippines, Japan; intertidal to 50m ( OBIS, 2020c).

Remarks: This species has never previously been collected from Indian waters, and therefore does not appear in the detailed annotated list of Indian echinoderms compiled by Sastry (2007). It has been recorded from Sri Lanka by Döderlein (1888) and from the Maldives by Clark & Davies (1965). James (1986), thus, included it in his table of shallow-water species from ‘Indian Seas’, with positive records for ‘Sri Lanka’ as well as the ‘ Maldives & Lakshadweep’ regions. Based on this, Samuel et al. (2017) erroneously included it in their ‘updated checklist of echinoderms from Indian waters’. However, the present collection represents the first valid report of this species from the India’s exclusive economic zone (EEZ).

Figures

FIGURE 4. Ophiarachnella septemspinosa, IO/SS/ECD/00235. (a) live specimen, in situ, (b) preserved specimen, (c) arm base, dorsal view showing radial shields and dorsal arm plates, (d) disc, ventral view showing jaw apparatus, and proximal part of arms, (e) middle arm, ventral view showing enlarged ventral arm spines, and (f) proximal part of arm, lateral view showing number, size and arrangement of arm spines. Scale bar: 4mm.