Ophiactis macrolepidota Marktanner-Turneretscher, 1887

O’Hara, Timothy D. & Thuy, Ben, 2025, Seamount ophiuroids from the High Seas of the western Indian Ocean, Zootaxa 5718 (1), pp. 1-88 : 73

Ophiactis macrolepidota Marktanner-Turneretscher, 1887

Ophiactis macrolepidota Marktanner-Turneretscher, 1887: 298 , pl. 12(12–13). — Matsumoto, 1917: 155–156, fig. 37. — Clark, A.M. & Rowe, 1971: 104. — Rowe & Gates, 1995: 379.

Ophiactis delicata Clark, H.L., 1915: 260–261 , pl. 11(9–10). — Clark, A.M. & Rowe, 1971: 82–83, [according to Rowe & Gates, 1995].

Ophiactis parva Mortensen, 1926: 123 . — Mortensen, 1940: 70–71, fig. 5. — Clark, A.M. & Rowe, 1971: 82–83, 105, fig. 31d [according to Rowe & Gates, 1995].

Ophiactis acosmeta Clark, H.L., 1938: 262–264 . — Clark, A.M. & Rowe, 1971: 82–83, 104 [according to Rowe & Gates, 1995].

STUDY MATERIAL. — MD208 : stn WB05 , Walters shoal, Zone sommitale Sud, 33° 15.12´S, 43° 54.514´E, 26– 30 m, 1/5/2017: 2 ( MNHN IE.2023.4158) ( DNA code= IE.2023.4158) . — MD208 : stn WS08, Walters shoal, Zone sommitale, Sud-Est, 33° 13.722´S, 43° 55.8861´E, 30–33 m, 3/5/2017: 2 ( MNHN IE.2023.4172) . — MD208 : stn WB09 , Walters shoal, Zone Sommitale Nord Ouest, 33° 13.767´S, 43° 55.7751´E, 27–30 m, 4/5/2017: 1 ( MNHN IE.2023.4168) . — MD208 : stn WB10 , Walters shoal, Zone Sommitale Nord Ouest, 33° 9.131´S, 43° 51.7939´E, 30 m, 6/5/2017: 1 ( MNHN IE.2023.4173) .

COMPARATIVE MATERIAL EXAMINED. Ophiactis definita Koehler, 1922a : BIOPAPUA/DW3770, Jacquinot Bay (Nouvelle-Bretagne), 5° 34´S, 151° 32´E, 220–294 m, 16/10/2010 , MNHN IE.2012.222 ( DNA code= ODF2 ). Ophiactis dyscrita H.L. Clark, 1911 : Sagami Bay , off Misaki, stn1, 35° 8.415´N, 139° 32.944´E to 35° 8.262´N, 139° 32.746´E, 109–160 m, 4/6/2018 , MV F248398 ( DNA code=Misaki031). Ophiactis macrolepidota Marktanner-Turneretscher, 1887 : KANACONO/DW4724, W Ile des Pins , 22° 39.6´S, 167° 8.3002´E to 22° 39.5´S, 167° 7.1795´E, 260– 255 m, 20/8/2016 , MNHN IE.2013.11110 ( DNA code= IE.2013.11110). SAYA / CP5433 , SW Saya de Malha , 11° 41.947´S, 61° 11.853´E to 11° 42´S, 61° 12.327´E, 234–235 m, 15/11/2022 , MNHN IE.2023.4233 ( DNA code= IE.2023.4233). Ophiactis plana Lyman, 1869 : MIRIKY/CP3178, entre Nosy-bé et Banc du Leven, 12° 58.88´S, 48° 9.09´E to 12° 59.01´S, 48° 9.0402´E, 378–380 m, 25/6/2009 , MNHN IE.2023.4013 ( DNA code=CP3178a).

Description. Disc to 1.6 mm dd; typically 6 arms (one 1 mm dd specimen MNHN IE.2023.4168 with only 5 arms), 3 arms thinner so fissiparous, 3 times dd; disc scales rounded, small, overlapping, primary plates not prominent, few to no disc spines; radial shields small, 2x l/w, separated; ventral scales present; oral shields spearhead shaped with a sharp proximal angle and a slightly lobed distal margin, as long as wide; adoral shields separated radially; 1 small distal oral papilla; basal dorsal arm plates almost oval, tapered proximally, 1.5–2 times as wide as long, subsequent plates more triangular, separated or just contiguous throughout; 3 short, blunt arm spines, middle spine largest; tentacle scale half as long as ventral arm plate. Colour: dorsal arm surface pinkish/brown; disc brownish-yellow.

Distribution. NW Pacific ( 0–67 m), W Indian Ocean ( 3–235 m), E Indo-W Pacific ( 0–294 m), S Africa ( 26–33 m), S Australia ( 1–196 m), New Zealand ( 0–27 m).

Remarks. Clark & Rowe (1971) remarked on the difficulty of separating small Ophiactis species that have 6 arms, one distal oral papilla, and divide by fission. Characters used to separate these species, such as the shape of the oral/adoral/radial shields, arm spines and the presence of disc spines, are morphologically variable, and Rowe & Gates (1995) proceeded to synonymise O. parva , O. delicata , O. acosmeta with O. macrolepidota . The Indonesian O. brachyura Döderlein, 1898 and the Japanese O. dyscrita could also be added to this list. In contrast, our DNA evidence suggests that there are multiple clades of such species, with overlapping species ranges, that may contain both 5- and 6-armed individuals. The COI sequence of the MD 208 specimen clusters with a 6-armed specimen from New Caledonia (IE.2013.11110) and two 5-armed specimens from Papua New Guinea (IE.2012.222). The latter specimens are larger, have purple arms, a bulbous pale disc, tiny radial shields and 4 arm spines at the base. Until type material (or neotypes from the type locality) are sequenced, it remains problematic to determine whether this clade is a new species or can be associated with an existing available name.