Ophiosphalma glabrum

Ophiosphalma glabrum (Lütken & Mortensen, 1899) Fig. 2H‒M Ophiomusium glabrum Lütken & Mortensen, 1899: 132‒123, pl. 4, figs. 7‒9.—H.L. Clark 1913: 213; 1917: 449‒450.— Koehler 1922: 405. Ophiomusium multispinum H.L. Clark, 1911: 113‒114, fig. 42.— Baker 2016: 31. Ophiomusium fimbriatum Koehler, 1922: 403‒405, pl. 90, figs. 6‒8.— Baker 2016: 31. Ophiosphalma glabrum. Baker 2016: 31, figs. 51a‒d. Material examined. 367 individuals at six stations. TALUD XII, Sta. 8, 20 ind. (ICML-EMU-11060); Sta. 15, 3 ind. (ICML-EMU-11072); Sta. 25, 288 ind. (ICML-EMU-11061), 14 ind. (ICML-EMU-11062), 7 ind. (ICML-EMU-11066), and 3 ind. (ICML-EMU-11683). TALUD XVIB, Sta. 1, 1 ind. (ICML-EMU-11092); Sta. 9, 1 ind. (ICML-EMU-11064-A), 14 ind. (ICML-EMU-11064-B), and 2 ind. (ICML-EMU-11065); Sta. 15, 14 ind. (ICML-EMU-11063). Comparative material. Ophiomusium glabrum Lütken & Mortensen, 1899, syntypes, 86 ind.: MCZ OPH-452, MCZ OPH-453, MCZ OPH-454, MCZ OPH-455, MCZ OPH-780, MCZ OPH-880, MCZ OPH-1021, MNHN-IE-2013-10254, USNM 19494, USNM 19496, USNM 19498, USNM 19499, USNM 19500 (Supplementary file 2). Description (ICML-EMU-11061). DD = 31 mm. Disc pentagonal, flat. Dorsal disc covered with imbricated, irregular scales. RS longer than broad, prominent, separated by numerous elongated scales of different sizes; one triangular plate with rounded edges between each pair of RS (Fig. 2H). Ventral interradii covered by oval imbricated scales, larger than dorsal scales. Genital slits with numerous quadrangular papillae (Fig. 2I). OSh almost as broad as long, triangular. One irregular madreporite, slightly larger than OSh. AdSh longer than broad, elongated, broader distally, meeting in front of OSh. Jaws bearing 6‒7 papillae at each side, quadrangular, merging, two distalmost the largest; one pointed papilla at jaw tips. Teeth four, similar to papilla at jaw tips (Fig. 2J). Arms gradually narrowing distally. Dorsal arm base with 3‒4 imbricated DAP, with a granular appearance, projecting laterally. DAP as long as broad, rhombic, proximally meeting and gradually separating and decreasing in size distally (Fig. 2K). First VAP smaller than rest; subsequent three VAP the largest (almost covering all arm segment length), almost meeting, the only ones with tentacle pores; posterior VAP triangular, reduced in size (1/3 arm segment in length), separated from each other. LAP with 6‒9 ArSp, short (approximately 1/5 LAP in length), pointed, separated; ventralmost ArSp slightly longest than rest. Three tentacle pores with one abradial pointed TSc (approximately 3.5 arm segments in length) and 1‒2 smaller adradial TSc (Fig. 2L). Color pattern beige (Fig. 2H‒M), center of dorsal disc light brown (ethanol preservation) (Fig. 2H). Habitat and distribution. Widely distributed in the eastern Pacific: British Columbia, Canada, Washington, USA, Mexico, Costa Rica, Panama, Colombia, Ecuador, and Peru; 878‒ 5,203 m depth, muddy substrates (Lütken & Mortensen 1899; Luke 1982; Maluf 1988; Lambert & Boutillier 2011). The material examined was collected off western Baja California, Colima, and Guerrero; 1,858 ‒2,125 m depth. Remarks. The specimens of the ICML-EMU-11061 lot presented some morphological differences compared to specimens of the type series, including: 1) three and rarely five tentacle pores, 2) the largest specimens can have up to 12 arm spines, and 3) some specimens have conspicuous primary plates. In Mexico, O. glabrum has been documented in western Baja California and Baja California Sur, the Gulf of California, and Oaxaca (GranjaFernández et al. 2015). The material examined herein was collected off Colima and Guerrero, representing new records for these areas, thus filling the previously known distribution gap in western Mexico.

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