Ophioplinthaca semele (A. H Clark, 1949)

Fig. 14

Ophiomitra semele A. H Clark, 1949: 20-23, fig. 8a, b.

Ophioplinthaca semele: O’Hara and Stöhr 2006: 76; Chen et al. 2021a: 14-18, fig. 6-8.

Material examined.

Northwest Pacific • 1 specimen; near Mariana Trench, Southeast of Guam Island, seamount, 12°6.67'N, 141°37.27'E; depth 1160 m; 03 September 2019; Collecting event: stn. SC033; Shenhaiyongshi msv leg; preserved in -80 °C; GenBank: OK043835, IDSSE-EEB-SW0113 .

Distribution.

537-1987 m depth, southwest of Guam Island, Northwest Pacific, Hawaii Islands.

Remarks.

Ophioplinthaca semele was first described by A. H Clark (1949) in the genus Ophiomitra, then redescribed by Chen et al. (2021a), and that recent study included rich morphological information. Ophioplinthaca semele from the present study concurs largely with the holotype description and Chen et al. (2021a), but it differs slightly in the disc stumps at the periphery of the disc. According to the holotype description, the disc stumps had a thorny tip or three thorns in the disc center, but at the periphery these stumps were smooth. Our specimen has a crown of somewhat longer thorns, both in the center and periphery of the disc (Fig. 14A-H). Ophioplinthaca dipsacos (Lyman, 1878) is one of the species that most closely resemble Ophioplinthaca semele by having a similar number and shape of arm spines, radial shield characters, number of lateral oral papillae, similar disc spines, and separated dorsal and ventral arm plates, but it differs in the number of tentacle scales at the first to third tentacle pore, and in the shape of the tentacle scale (Table 3). Moreover, O. dipsacos was recorded from the Gulf of Mexico, far from the known distribution of O. semele (Lyman, 1878). Ophioplinthaca globata, O. lithosora, O. citata, and O. clothilde show a similar shape of the disc spines, but differ in size and other morphological characters (Table 3). Therefore, variations within species from our collection can be considered as intraspecific variation, rather than species delimiting characters.