Ophiothela venusta (de Loriol, 1900 )

Peyghan, Soroor, Doustshenas, Babak, Nabavi, Mohammad Bagher, Rounagh, Mohammad Taghi, Larki, Amir Ashtari & Stöhr, Sabine, 2018, New records of the brittle stars Ophiothela venusta and Ophiactis modesta (Echinodermata: Ophiuroidea) from the northern Persian Gulf, with morphological details, Zootaxa 4527 (3), pp. 425-435 : 427-431

Ophiothela venusta (de Loriol, 1900)

Figs 2–4

Ophiocnemis venusta de Loriol, 1900: 81 , pl. 8 figs 2, 3.

Ophiothela venusta —Cherbonnier & Guille 1974: 160–162, pl. 9 figs 1–6, fig. 62A–D, Price 1983: 65, fig. 28. Ophiopsammium nudum H. L. Clark, 1923: 341 .

Ophiothela nuda — A. M. Clark 1974: 469, A. M. Clark & Courtman-Stock 1976: 141.

Ophioteresis beauforti Engel, 1949: 140 –143, fig. 1, pl. 7 figs 1–4.

Ophiothela beauforti — Balinsky 1957: 22, pl. 4 fig. 16.

Material examined: Ophiothela venusta , 104 specimens, northern Persian Gulf , port of Bushehr, on octocorals on shipwrecks, May 2015 and May 2016. Ophiopsammium semperi , paratype, Philippines, collected by S. Semper, late 1800s [SMNH-Type-5236] .

Size range: Disc diameter 2–8 mm, arm length 7–35 mm.

Description: Arms coiled around the branches of gorgonians Euplexaura sp. and Echinomuricea sp. ( Fig. 2 ). Colouration of live specimens is very variable: grey, yellow and black, red, blue, orange with black bands, purplish black. Colour ultimately changes after preservation in alcohol: grey, cream with brown or yellow, orange with black, completely black ( Fig. 3 A–C). The specimens accord well with the description given for O. venusta by Price (1983).

Five non-branching arms, plates obscured by thick skin. Disc rounded pentagonal, variable between individuals, and generally this species is highly polymorphic. Dorsal disc and arms covered with finely rugose, low, round and some higher conical granules in various combinations, often higher in the disc centre, low and round on the arms, obscuring radial shields, plates and scales ( Fig. 3A 1, B1 , C). Ventral disc and arms without granules ( Fig. 3A 2, B2 ). Radial shields scalene triangular, almost meeting in the disc centre, in contact along almost their entire length, distally separated by a dorsal arm plate ( Fig. 3E 1 ). Dorsal arm plates fragmented, on each arm joint several small, irregular platelets ( Fig 3D 1 ). Oral papillae absent. Oral shield drop-shaped, with proximal acute angle, strongly convex distal and lateral edge, smaller than adoral shields. Madreporite larger than other oral shields. Adoral shields in contact proximally, broadly oval to quadrangular, restricted to the proximal part of the oral shield ( Fig. 4B ). Each jaw bears a cluster of tooth papillae on the ventral half of the dental plate, block-like teeth on the dorsal half ( Figs 3D3 , 4B, C, D ). Ventral arms covered by thickened skin without granules, translucent in dried animals. Ventral arm plates separated, first plate narrow, longer than wide, second hexagonal, about as long as wide, further out up to twice as wide as long at distal edge, proximal edge half as wide as distal ( Figs 3D3 , 4C ). No tentacle scales. Arm spines up to 5, minutely thorny, tapered, shortest spine dorsal, middle spine longest, slightly longer than an arm joint. Vertebrae with distalwards directed keel and proximal deep groove ( Figs. 3E 1 , 4E ). Arm spine articulations with two thick lobes, connected by a thin bridge, surrounding large nerve and muscle openings ( Fig. 4B ).

Depth distribution: 1.5–32 m depth. In the present study collected between 2 and 26 m.

Geographic distribution: Persian Gulf ( Mortensen 1940; Price 1983) Eastern Africa and Madagascar, East Indies ( A. M. Clark & Rowe 1971), South Africa ( A. M. Clark 1974) Australia ( Rowe & Gates 1995).

Remarks: Ophiothela venusta is recorded for the first time from the northern Persian Gulf (Iranian coasts) by this study. Individuals live associated with gorgonians in tropical areas. The species is found in subtidal artificial reefs and coral reefs (probably always attached to gorgonians). Ophiothela venusta is an abundant species in the reef environment of the Persian Gulf but it has not been reported before, possibly due to technical problems with sampling on subtidal substrates and lack of clear keys for certain identification. Also, O. venusta is extremely variable in colour pattern and disc covering (granules, spines), which can make it hard to identify. It has been described multiple times under various names in several genera, which were finally recognized as conspecific by Cherbonnier & Guille (1978). We noted possible confusion of species in historical records. Ophiothela venusta has been described as a variable species with respect to dorsal disc covering ( Cherbonnier & Guille 1978), from a dense coat of small round granules with conical spines to individuals with few low, scale-like granules. Mortensen (1940) figured several specimens of Ophiopsammium semperi with vivid colour pattern, sporting dark and light banded arms and large spots on the disc, encircled in white. Such a vivid and variable colouration is typical for O. venusta , whereas the original description of O. semperi suggests a more subdued colouration ( Lyman 1874). Examination of a paratype of O. semperi showed that the species is covered by a dense, uniform coat of extremely small round granules on the dorsal disc and arms, including the lateral arm plates, and extending slightly onto the ventral disc. Only the ventral arms, most of the ventral disc and the oral frame are free from granules. The granules are smaller than those of O. venusta . The thick skin obscures all plates. Based on these observations, it seems likely that Mortensen's specimens were not O. semperi but O. venusta .

Mortensen (1940) synonymized Ophiopsammium semperi with Ophiopsammium rugosum Koehler, 1905 , regarding the differences in granulation as mere variation. A. M. Clark (1965) reported individuals of Koehler’s species with similar conical spines at the disc edge and in the disc centre. These specimens are similar to some of the specimens of O. venusta figured by Cherbonnier & Guille (1978), and given the possible misapplication of the name O. semperi by Mortensen, it is possible that O. rugosum may be conspecific with O. venusta but not with O. semperi . Hence, the limits between these species and between the genera Ophiopsammium and Ophiothela appear blurred at present.

Figures

FIGURE 1. Location of the two shipwrecks studied, an unnamed barge and “Raffaello” in the Persian Gulf, Bushehr harbour, Iran.

FIGURE 2. Live specimens of Ophiothela venusta associated with the gorgonian Euplexaura sp. A, note the high number of brittle stars (>10) and their colour variability with red–black–white bands, white–red, yellow–red and uniformly greyish–green animals. B, magnified upper right quarter of A, upper animal with wider dark blue and red bands, separated by thin white bands, lower animal with wide white and narrower red bands. Scale bars in millimetre.

FIGURE 3. Ophiothela venusta from the Persian Gulf. A-C, variation in colour pattern in preserved and dried specimens, colours have faded, and red has turned to yellow (A, B). D, specimen treated with bleach (NaOCl) to remove the outer epidermis and part of the granules, radial shields mostly exposed, ventral side still covered by translucent skin. E, skin completely removed by longer treatment with bleach (NaOCl), exposing arm vertebrae, dental plates, oral plates (jaws), genital plates and radial shields. DP, dental plate, GP, adradial genital plate, LAP, lateral arm plate, OP, oral plate, RS, radial shield, V, vertebra, VAP, ventral arm plate, TP, tooth papillae. Scale bars in millimetre.

FIGURE 4. SEM images of Ophiothela venusta, ventral aspects. A, thick skin obscures all skeletal features. B, skin removed, exposing the skeleton, oral frame. C, ventral skeleton and radial shields from below. D, teeth and few remaining tooth papillae, oral plates. E, series of arm vertebrae, lateral aspect. AS, adoral shield, DP, dental plate, GP, genital plate, k, keel, LAP, lateral arm plate, M, madreporite, OP, oral plate, OS, oral shield, PB, podial basin of second tentacle pore, RS, radial shield, SA, spine articulation, T, tooth, TF, second tube foot, TP, tooth papillae, V, vertebra, VAP, ventral arm plate. Scale bars in millimetre.