Ophionereis sykesi, O’Hara, 2015

O’Hara, Timothy D., 2015, Enigmatic ophiuroids from the New Caledonian region, Memoirs of Museum Victoria 73, pp. 47-57 : 49-52

Ophionereis sykesi sp nov

Fig. 2

Zoobank LSID. http://zoobank.org/ urn:lsid:zoobank.org:act:

F6388E19-397A-482A-90A8-1DA7BE551083

Type material. -- New Caledonia. BIOCAL: stn CP110, Ride de Norfolk , 22° 12.38'S, 167° 6.43'E, 275-320 m, 9 Sept 1985, holotype ( MNHN IE.2013.16002); paratypes, same locality: 26 ( MNHN IE.2013.16003) .

Other material examined. -- New Caledonia . -- Bathus 1: stn DW688, Côte est, 20° 33.17'S, 165° 0.37'E, 270-282 m, 1993: 14 ( MNHN IE.2013.6536) . -- Bathus 2: stn DW716, Sud-ouest, 22° 40.81'S, 167° 12.07'E, 290-308 m, 1993: 1 ( MNHN IE.2013.6541) . -- Bathus 2: stn DW717, Sud-ouest, 22° 44.02'S, 167° 16.58'E, 350-393 m, 1993: 1 ( MNHN IE.2013.6542) . -- EBISCO: stn DW2559, NW Bellona , 20° 28'S, 158° 41'E, 255-280 m, 2005: 1 ( MNHN IE.2007.5401) . -- EBISCO: stn CP2592, Plateau des Chesterfield , 19° 42'S, 158° 30'E, 273-281 m, 2005: 1 ( MNHN IE.2007.5174) . Musorstom 6: stn DW399, Ride des Loyauté, 20° 41.8'S, 167° 0.2'E, 282 m, 1989: 1 ( MNHN IE.2013.6537) . -- Musorstom 6: stn DW418, Ride des Loyauté, 20° 41.75'S, 167° 3.35'E, 283 m, 1989: 1 ( MNHN IE.2013.6538) . -- Musorstom 6: stn DW422, Ride des Loyauté, 20° 26.2'S, 166° 40.31'E, 257 m, 1989: 1 ( MNHN IE.2013.6539) . -- Musorstom 6: stn DW423, Ride des Loyauté, 20° 25.85'S, 166° 40.5'E, 280 m, 1989: 9 ( MNHN IE.2013.6540) . -- SMIB5 : stn DW95, 22° 59.7'S, 168° 19.8'E, 140-200 m, 1989: 1 ( MNHN IE.2013.6544) . -- SMIB5 : stn DW96, 23° 0'S, 168° 18.7'E, 245 m, 1989: 1 ( MNHN IE.2013.6545) . -- Vanuatu. GEMINI: stn DW50, Mont Gemini , 20° 59.1'S, 170° 3.5'E, 425 m, 1989: 1 ( MNHN IE.2013.6543) .

Comparative Material. Ophionereis degeneri (A.H. Clark, 1949) : FFS-0021, French Frigate Shoals , 23° 51.792'N, 166° 11.052'W, 85 m, 12/10/2006, UF 6679 . FFS-0026, French Frigate Shoals , 23° 51.702'N, 166° 11.112'W, 12 m, 12/10/2006, UF 6039 . Ophionereis variegata Duncan, 1879 : BIOLUM/21, Lizard Is , Big Vicki, 14° 41.4'S, 145° 26.2'E, 2-4 m, 26/10/2005, MV F109863 (3) . BIOLUM/30, Lizard Is , 7-14 m, 26/10/2005, MV F109864 (1) . CReefs/GD.HI08-10, Heron Island , south side, 23° 28.4'S, 151° 57.83'E, 18 m, 6/9/2008, MV F211039 (4) . HI09-011, Heron Island , Pinnacle, 23° 28.333'S, 151° 57.028'E, 9-10 m, 13/11/2009, UF 9963 . HI09-018, Heron Island , Sykes Reef, 23° 25.943'S, 152° 2.025'E, 30 m, 14/11/2009, UF 9988 . HI09-098, Heron Island , 23° 27.193'S, 151° 54.027'E, 24-26 m, 24/11/2009, UF 10115 .

Description. Disc round, 10.4 mm diameter, arms at least 12 times d.d. (arm tips all broken). Disc covered in rounded overlapping scales, up to 0.35 mm diameter, primaries evident but small, centrodorsal 0.4 mm diameter, approximately 18 plates between centrodorsal and interradial margin, marginal plates slightly larger than adjacent ones, forming a rim to the disc. Radial shields 1.0 mm long, twice as long as wide, roughly oval or triangular, with a truncate distal margin, convex lateral sides and an acute to rounded proximal angle, separated radially by 3 series of plates, the middle ones flanked by a row of smaller plates on either side. An irregular series of small papillae are present along the disc margin over the arm base, papillae conical with a blunt tip.

Ventral disc covered in similar overlapping plates as the dorsal surface, approximately 13 plates between oral shields and margin. Genital slits bordered interradially by an irregular series of rounded granules, obvious near the oral shield, becoming cuboid and contiguous from mid-radius to the disc margin (and often hidden within the slit), confluent with the papillae over the dorsal arm base. Oral shields rhomboid, just longer than wide, with rounded angles, and slightly concave sides. Adoral shields long and slender, tapering to a point proximally, rounded and widest distally, not contiguous with neighbouring plates, oral plates visible towards the jaw tip. Five oral papillae, inner papillae longest and orientated proximally so that they appear like infradental papillae on amphiurids; next two papillae rhomboid to rectangular with flattened edge facing the jaw slit, fourth papillae 1.5 times as wide as high, rounded distally, touching the adoral shield, and finally a small recurved papilla at the end of the slit, sitting at the junction of the adoral plate and first ventral arm plate, protecting the second oral tube foot. Five teeth, dorsal three largest with thick enamelled tips, ventral one sits above the inner oral papillae.

Dorsal arm plates 0.75 mm wide, 1.8 times as wide as long, broadly contiguous throughout arm, hexagonal with a straight distal edge, straight distolateral sides that are contiguous with the supplementary arm plate, straight proximolateral sides contiguous with the lateral arm plate, proximal edge overlayed by preceding plate. Basal supplementary dorsal arm plates small, roughly triangular, widest distally, extending proximally to the angle between the disto- and proximo-lateral sides of the dorsal arm plates, mostly lateral in position on the arm, appearing narrow and droplet-shaped from a dorsal projection. Dorsal arm plates become progressively more triangular in shape as the distolateral sides shorten and the proximolateral sides lengthen. Near the arm tip the distal side becomes convex and the proximolateral sides converge so that succeeding plates are only contiguous for 1/3 of their width. The supplementary plate becomes progressively smaller but persists as a tiny plate to (near) the arm tip. No accessory lateral arm plates, instead there is a decalcified gap between neighbouring lateral arm plates, the supplementary dorsal arm plate and the tentacle pore. First ventral arm plate diamond shaped, wider than long, the proximal sides contiguous with the adoral shields and distal oral papillae, the distal angle overlaps the second arm plate. Succeeding plates roughly quadrangular, as wide as long, with convex distal and proximal sides and concave lateral sides that border the tentacle pore, contiguous for 2/3 of their width. Second ventral arm plate with conspicuously convex distal edge. Plates becoming longer than wide near the arm tip, with convergent proximolateral sides, plates here contiguous for only 1/3 of their length.

Two arm spines on basal two segments, thereafter 3, slightly flattened to rounded, straight or slightly curved, blunt apex, on the first free segments the uppermost arm spine is 1.35 mm long, middle 1.5 mm long (to 1.7 segments long) and lowest 1.3 mm long. All 3 spines persist to the arm tip, slender, subequal to 1.2 segments in length. One thick ovoid tentacle scale, to 3/4 of a segment long, hinged on the ventral arm plate; a smaller rim-like scale on the ventral plate, usually overlain by the larger one. The ovoid scale persists to the arm tip.

Colour (dried). White with brown markings, notable on the proximal edge of large disc scales and around the interradial rim of the radial shields. Dorsal arm plates with dark patch at the centre of the distal edge, with white markings on either side. Arm spines with faint brown bands near the base and around the tip, brown markings around the periphery of the oral shields and on some basal ventral arm plates.

Paratype variations. From 4 to 10 mm dd. Some dorsal arm plates are darker in colour, forming narrow bands of 1-2 segments on the arms, alternating with bands of 3-5 lighter segments.

Distribution. New Caledonia (140-393 m), Vanuatu (425 m).

Remarks. The new species is very similar in overall appearance to Ophionereis novaezelandiae Mortensen, 1936 known from the outer shelf and upper slope of southern Australia (formerly as O. terba Baker & Devaney, 1981 ) and the north-eastern coast of New Zealand to the Kermadec Islands ( O’Hara 1998, Mills & O’Hara 2013). This species differs however, in lacking the papillae around the dorsal arm base, slightly narrower dorsal arm plates (generally less than 1.7 times as wide as long), and arms that form tight horizontal coils (see Mills & O’Hara 2013, fig. 13b). The colour scheme is also brighter on O. novaezelandiae ; the two white patches on either side of the distal midline of the dorsal arm plates are rimmed by a darker colour forming characteristic ‘m’ shaped markings. The differences between these species are slight but consistent. The dorsal papillae are always present on specimens of the new species, including small specimens of only 5 mm d.d..

Both Ophionereis fusca Brock, 1888 and O. sasakii A.M. Clark, 1953 have some genital papillae that extend around the arms until the dorsal surface. However, the papillae are restricted to the dorsolateral sides of the arm and are discontinuous radially, i.e. not present distal to the area between the radial shields. While the genital papillae on O. fusca are contiguous and blunt, like O. sykesi , they are separate, spiniform and pointed on O. sasakii . Ophionereis fusca is covered in prominent dots (see A.M. Clark 1953, fig. 5) and O. sasakii has thick bands of colour on the arms, the dark and light sections being both approximately 6 segments long. Dorsal papillae or spines are also characteristic of the genus Ophiodoris , however, the species in that genus do not have any supplementary arm plates.

There are specimens of another diminutive Ophionereis from northern Australia, with similarly patterned dorsal arm plates to O. novaezelandiae , which has been assigned by Rowe & Gates (1995) to the Korean species O. variegata Duncan, 1879 . The dorsal arm plates of these specimens have a dark spot in the middle of the distal rim, surrounded by a ‘V’-shaped patch of white, which in turn is bordered by two dark longitudinal lines. The arms are also banded, with 2 (rarely to 4) dark segments to every light segment. These specimens have been generally found from 5 to 100 m depth, often living in the small holes of dead coral pieces, and only observed by scuba divers at night (O’Hara, personal observations). Ophionereis variegata (including the Australian specimens) differs from other species in having small accessory lateral arm plates, wedged between the supplementary dorsal arm plate and the tentacle scale. It is unclear whether the Australian specimens are really conspecific with O. variegata as the arm length appears to be considerably longer (to eight times d.d.) than the four to five times disc diameter reported from Korea ( Duncan 1879), Japan ( Matsumoto 1917 as O. porrecta ) and China ( Liao & Clark 1995). Another similar species, O. lineata H.L. Clark, 1946 , has been described from the southern Great Barrier Reef. We have seen unpublished photos of this species from the Great Barrier Reef Seabed Biodiversity Project ( Pitcher et al. 2007) which confirm the type specimen’s distinct colour pattern (figured by Clark & Rowe 1971 and Baker & Devaney 1981), having three to five light segments alternating with one to two darker ones, and a dark longitudinal line running down the centre of the dorsal arm surface bordered by two lighter lines, in turn bordered (on the lighter segments) by a dense pattern of small dots. Ventrally there are two faint longitudinal dark lines or series of dots. Two other species that can have two prominent white dots on each dorsal arm plate, O. olivacea H.L. Clark, 1901 and O. squamulosa Koehler, 1913 from the Caribbean (see Hendler 1995 fig. 51), may also be related. Finally, O. degeneri A.H. Clark, 1949 described from Hawaii, with similar specimens reported from New Caledonia ( Stöhr 2011), differs from the other species in having small circular disc scales and no prominent primary plates (see Stöhr 2011 fig. 15). Moreover, specimens from Hawaii (UF) do not have white markings on the dorsal arm plates. Thus, in conclusion, the Australian specimens of ‘O. variegata’ possibly represent a new species, but this requires confirmation from a thorough morphological or molecular comparison with northern Pacific populations. None of these species have the marginal disc papillae running over the dorsal arm base that are found in O. sykesi .

A new genus-level revision of the Ophionereididae / Ophiochitonidae is required. The ophiuroid phylogenies of O’Hara et al. (2014) and Hugall et al. (2015) show that the Ophiochitonidae is paraphyletic with respect to the Ophionereididae . There is a morphological transition from Ophiochiton , Ophioplax and Ophiodoris with no supplementary dorsal arm plates, through Ophionereis australis (H.L. Clark, 1923) where they are restricted to a few basal segments, to O. novaezelandiae with small supplementary plates that persist down the arm, and finally to O. annulata ( Le Conte, 1851) and O. schayeri ( Müller & Troschel, 1844) where there are large persistent supplementary arm plates. The new species is assigned provisionally to Ophionereis sensu lato but we anticipate a future revision that recognises a clade including at least this species, O. novaezelandiae , O. variegata , O. lineata and O. degeneri at the genus or subgenus level of classification.

Etymology. Named after the wife of TOH, Deborah Sykes, who has had to put up with him rummaging around the world’s museum collections for years.