Ophiomusa lymani (Wyville-Thomson, 1873)

Fig. 4A‒F

Ophiomusium lymani Wyville-Thomson, 1873: 174‒175, figs. 32‒33.—Lütken & Mortensen 1899: 137‒139, pl. 3, figs. 8‒ 11.— H.L. Clark 1913: 213‒214; 1917: 450; 1923: 154.— Kyte 1969a: 1738.— Tyler 1980: 129, fig. 2a‒b.— Martynov & Litvinova 2008: 87, 90, fig. 6h.

Ophiomusa lymani . O’Hara et al. 2018: 8.— O’Hara & Thuy 2022: 13‒14, fig. 5a‒g.

See Paterson (1985) and O’Hara & Thuy (2022) for other synonymous records.

Material examined. 1,108 individuals at 15 stations. TALUD IV, Sta. 14, 2 ind. (ICML-EMU-11073). TALUD XII, Sta. 5, 23 ind. (ICML-EMU-11074); Sta. 8, 1 ind. (ICML-EMU-11075-B); Sta. 9, 1 ind. (ICML-EMU-11075-A); Sta. 24, 3 ind. (ICML-EMU-11076); Sta. 25, 178 ind. (ICML-EMU-11077); Sta. 29, 249 ind. (ICML-EMU-11078), 259 ind. (ICML-EMU-11079), and 2 ind. (ICML-EMU-11684). TALUD XVIB, Sta. 1, 2 ind. (ICML-EMU-11080- A) and 1 ind. (ICML-EMU-11080-B); Sta. 9, 2 ind. (ICML-EMU-11081), 6 ind. (ICML-EMU-11082), and 35 ind. (ICML-EMU-11083); Sta. 15, 40 ind. (ICML-EMU-11084) and 59 ind. (ICML-EMU-11085); Sta. 20, 15 ind. (ICML-EMU-11086); Sta. 21, 2 ind. (ICML-EMU-11087); Sta. 22, 5 ind. (ICML-EMU-11088); Sta. 27, 194 ind. (ICML-EMU-11089-A), 1 ind. (ICML-EMU-11089-B), and 18 ind. (ICML-EMU-11090); Sta. 28, 10 ind. (ICML-EMU-11091).

Comparative material. Type material not examined. While examining material deposited at the British Museum of Natural History, Baker (2016) designated a lectotype (BMNH 90.2.19.9.10) and a paralectotype (no catalog number available) of O. lymani . Unfortunately, it was impossible to examine these specimens during the present work.

Description (ICML-EMU-11078). DD = 23 mm. Disc round, flat. Dorsal disc with strongly tuberculous appearance, mainly on RS and large marginal interradial plates; covered with imbricated, irregular scales. Primary plates not evident, except for a central polygonal primary plate. RS longer than broad, triangular, very conspicuous, separated by a single row of scales; one pentagonal plate at disc margin between each pair of RS with tuberculous appearance (Fig. 4A). Ventral interradii covered by few irregular scales, much larger than dorsal scales (Fig. 4B). OSh longer than broad, pentagonal proximally, quadrangular distally. Madreporite not evident. AdSh longer than broad, elongated, rectangular, meeting in front of OSh. Jaws bearing 5‒7 papillae at each side; AdShSp rectangular, elongated, the largest; 2AdShSp rectangular, smaller than AdShSp; BSc similar in shape, larger than 2AdShSp; IPa quadrangular; 2IPa at jaw tips, similar to IPa. vT rounded (Fig. 4C). Arms slender. First two DAP much reduced, overlapping; subsequent DAP slightly broader than long, rhombic, small (approximately 1/3 LAP in length), separating, decreasing in size distally (Fig. 4D). First VAP smaller than rest; subsequent two VAP pentagonal, almost meeting, the only ones with tentacle pores. Posterior VAP lacking. LAP with up to seven ArSp, very short (approximately 1/5 LAP in length), pointed. Two tentacle pores with one oblong TSc fully covering all the pore (Fig. 4E). Color pattern beige-whitish (ethanol preservation) (Fig. 4A‒F).

Habitat and distribution. Widely distributed in the Pacific, Indian, and Atlantic Oceans (Paterson 1985). In the eastern Pacific from British Columbia, Canada, to Chile; 630‒ 2,906 m depth, muddy and sandy substrates (Lütken & Mortensen 1899; Maluf 1988). The material examined was collected off western Baja California, in the entrance of the Gulf of California, and off Jalisco, Colima, and Guerrero; 1,392 ‒2,250 m depth.

Remarks. The material examined here presented up to seven arm spines; however, Paterson (1985) indicated that this species could display up to 12 arm spines. Ophiomusa lymani can easily be distinguished from the rest of the deep-water ophiuroids from the eastern Pacific by their tuberculous disc, the large radial shields (covering approximately ½ disc radius) with tuberculous surface, the presence of two tentacle pores, and the absence of ventral arm plates in almost the entire arm. Widely distributed in the eastern Pacific, but in Mexico only recorded in the Gulf of California, off western Baja California and Baja California Sur, and off Marias Islands (Granja-Fernández et al. 2015). Material from off Jalisco, Colima, and Guerrero represent new distribution records for these areas, including (Guerrero) the southernmost record in western Mexico.