Ophiacantha diplasia H.L. Clark, 1911

Granja-Fernández, Rebeca, Hendrickx, Michel E., Rangel-Solís, Pedro Diego & López-Pérez, Andrés, 2023, Deep-sea Ophiuroidea (Echinodermata) collected during the TALUD cruises in western Mexico, Zootaxa 5259 (1), pp. 1-71 : 33-35

Ophiacantha diplasia H.L. Clark, 1911

Fig. 8G‒L

Ophiacantha diplasia H.L. Clark, 1911: 209‒211 , fig. 97a‒c.— Boolotian & Leighton 1966: 7‒8, fig. 30.— Hendler 1996: 155‒157, fig. 7.16.— Lambert & Austin 2007: 78‒79, fig. 32‒33.

Ophiophthalmus diplasia . Kyte 1982: 508.

Material examined. 56 individuals at five stations. TALUD X, Sta. 4, 1 ind. (ICML-EMU-11181-A). TALUD XIV, Sta. 1, 1 ind. (ICML-EMU-11180); Sta. 20, 1 ind. (ICML-EMU-11181-B). TALUD XV, Sta. 1, 12 ind. (ICML-EMU-11183) and 4 ind. (ICML-EMU-11949); Sta. 23, 34 ind. (ICML-EMU-11182) and 3 ind. (ICML-EMU-11673).

Comparative material. Ophiacantha diplasia H.L. Clark, 1911 , holotype, 1 ind.: USNM 24647 . Paratypes, 79 ind.: MCZ OPH-3198 , MCZ OPH-3199 , MCZ OPH-3416 , MCZ OPH-3417 , MCZ OPH-3418 , USNM 25647 , USNM 26000 , USNM 26247 , USNM 26248 , USNM 26814 , USNM 26927 , USNM 26987 , USNM 27091 , USNM 27215 , USNM 27216 (Supplementary file 2).

Description (ICML-EMU-11183). DD = 10 mm. Disc circular. Dorsal disc covered by separated granules, those on the margin longer. Primary plates not evident. RS oval, separated ( Fig. 8G ). Ventral interradii covered by imbricated scales and some granules distally ( Fig. 8H ). OSh broader than long, diamond-shape with rounded edges. Madreporite with a rounded depression. AdSh longer than broad, slender, meeting in front of OSh. Jaws bearing six papillae at each side; AdShSp elongated, longer than rest; 2AdShSp elongated; LOPa three, similar in shape to 2AdShSp; IPa pointed ( Fig. 8I ). Arms gradually narrowing distally. First DAP covered by granules; subsequent DAP as long as broad, rhombic, meeting ( Fig. 8J ). VAP slightly broader than long, pentagonal, slightly separated from each other. LAP with 6‒7 ArSp, large (approximately 2.5 arm segments in length), smooth, dorsalmost the longest. Tentacle pores with two oval TSc, abradial much longer ( Fig. 8K ). Color pattern in dorsal disc and arms light brown ( Fig. 8G, J ), beige in ventral view (ethanol preservation) ( Fig. 8H ).

Habitat and distribution. British Columbia, Canada, Oregon and California, USA, and Mexico (H.L. Clark 1911; Lambert & Austin, 2007; Granja-Fernández et al. 2015); 71‒ 1,408 m depth ( Maluf 1988; Hendler 1996), sandy and rocky substrates, coral, death coral, and sponges (H.L. Clark 1911). The material examined was collected off western Baja California Sur and in the Gulf of California; 208‒850 m depth.

Remarks. Ophiacantha diplasia is highly variable in its external morphology (H.L. Clark 1911; Hendler 1996). The revision of the TALUD specimens and the type material corroborate this. The following morphological plasticity was observed in the examined specimens: 1) variability in oral shields shape, 2) different thickness of adoral shields (slender vs. broad), 3) jaws with up to 7‒8 papillae and presence of 1‒3 IPa, 4) small specimens (DD <15 mm) showed dorsal disc and interradius with granules but also with scattered spines (also observed by Hendler (1996)), this feature is possibly related to ontogenetic change (pers. comm. Sabine Stöhr, 2022), 5) radial shields of different lengths, 6) up to eight arm spines, and 7) some specimens featured three tentacle pores in the first arm segments. Moreover, we observed that this species easily loses its arms and disc during collection. Ophiacantha diplasia had been transferred to the genus Ophiophthalmus ( Kyte 1982) but was subsequently returned to Ophiacantha by Hendler (1996), who suggested that Ophiophthalmus was an invalid homonym ( Paterson 1985). However, the homonymy of Ophiophthalmus has been recently disproven by Nethupul et al. (2022), and this genus currently includes five species ( O. cataleimmoidus (H.L. Clark, 1911) , O. hylacanthus (H.L. Clark, 1911) , O. normani , O. relictus ( Koehler, 1904) , and O. serratus Nethupul, Stöhr & Zhang, 2022 ) characterized by ovoid and naked RS, 3‒4 spiniform lateral oral papillae, and a short jaw. These characteristics do not coincide with O. diplasia since the latter presents round and short RS, many oral papillae, and an elongated jaw, suggesting that it belongs to the family Ophiotomidae ( O’Hara et al. 2018) . Previously recorded off western Baja California, in the Gulf of California, and off the Revillagigedo Islands ( Granja-Fernández et al. 2015). The material from western Baja California Sur is a new distribution record for this area.

Figures

FIGURE 8. Ophiacantha costata Lütken & Mortensen, 1899 (ICML-EMU-11700, DD = 6 mm). A, Dorsal disc; B, Ventral disc; C, Mouth; D, Dorsal arm; E, Ventral arm; F, Dorsal view. Ophiacantha diplasia (H.L. Clark, 1911) (ICML-EMU-11183, DD = 10 mm). G, Dorsal disc; H, Ventral disc; I, Mouth; J, Dorsal arm; K, Ventral arm; L, Dorsal view.