Ophiacantha striolata Mortensen, 1933

O’Hara, Timothy D. & Thuy, Ben, 2025, Seamount ophiuroids from the High Seas of the western Indian Ocean, Zootaxa 5718 (1), pp. 1-88 : 46-47

Ophiacantha striolata Mortensen, 1933

Ophiacantha striolata Mortensen, 1933b: 322–324 , fig. 42–43. — Clark, A.M. & Courtman-Stock, 1976: 168–169, figs 169, 175, 180. — Clark, A.M., 1977: 135. — Olbers et al. 2019: 122–123, fig. 106–107.

STUDY MATERIAL. — MD208 : stn WB05 , Walters shoal, Zone sommitale Sud, 33° 15.12´S, 43° 54.514´E, 26–30 m, 1/5/2017: 1 ( MNHN IE.2023.4164) ( DNA code= IE.2023.4164) .

COMPARATIVE MATERIAL EXAMINED. Ophiacantha alternata A.M. Clark, 1966 : MRG/797, Flinders , bay side of West Head, 38° 29´S, 145° 2´E, 0–1 m, 7/3/2014 , MV F173963 ( DNA code=F173963). Ophiacantha indica Ljungman, 1867 : KGR/ Sled 12, King George River region, 13° 53.933´S, 127° 20.6148´E, 41 m, 7/6/2013 , MV F193489 ( DNA code=F193489) .

Distribution. South Africa to Southern Mozambique ( 84–412m), Walters Shoal ( 26–30 m)

Remarks. The single Walters Shoal specimen ( 3 mm dd) has short arms, barely 3x dd; the disc is covered in trifid disc spinelets with numerous thorns (see Mortensen 1933b) on thin perforated overlapping plates, including a few on the distal ends of radial shields, sparser ventrally; to 8 arm spines meeting dorsally, middle to lower ones with numerous thorns, upper more smooth, up to 2 segments in length, distally the lowest spine is a little curved; narrow jaw, 3 erect oral papillae, triangular oral shields, adoral shields extended radially, but separated by the first VAP; LAPs very striated; the single tentacle scale is 1/2 as long as segment, 2x as long as wide, striated with pointed or thorny tip, VAPs thin glassy and beaded. This specimen matches Mortensen’s type description and figures of O. striolata from eastern South Africa, especially the form of the disc spines, however, the tentacle scale is larger than the minute scale figured for the type. On our phylogeny ( Fig. 2b ) this specimen is sister to Ophiacantha indica and O. alternata both shallow water species from the East Indo-West Pacific and Southern Australia respectively.

Figures

FIGURE 2. Maximum likelihood phylogeny of the ophiuroid samples from JC066 and MD208 expeditions and comparative specimens. The phylogeny was created from 275 kb of nuclear DNA and 1431 bp of mitochondrial COI using RAxML v.8.1.20 47 GTRCAT model with 4 partitions (3 exon codon positions and COI) and converted to a chronogram using TreePLv1.0 and 11 fossil-based calibration points. Green samples are from Walters Shoal, blue samples from Coral, purple from Melville, and red samples from Atlantis Bank. Node labels are RAxML fast-bootstrap values (n=100). The tip labels are composed of the species name, sample code, bp of nuclear (415 genes) and mitochondrial (COI) DNA, geographic and depth distribution. Geographic codes:AN=Antarctic, AR=Arctic, AU=S Australia, EA=E Atlantic, EP=E Pacific, IN=Indian, IP=Indo-Pacific, NA=N Atlantic, NEP=NE Pacific, NWP=NW Pacific, NZ=New Zealand, SA=S Africa, SK=Kerguelen, SM=S America, WA=W Atlantic; depth codes: S=Shelf, B=Bathyal, A=Abyssal. (a) the orders Euryalida and Ophiurida, (b) Ophiacanthida and Ophioscolecida, (c) Amphilepidida and Ophioleucida.