Ophiosphalma variabile (Lütken & Mortensen, 1899 )

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 : 18-21

Ophiosphalma variabile (Lütken & Mortensen, 1899)

Fig. 3G‒L

Ophiomusium variabile Lütken & Mortensen, 1899: 135‒137 , pl. 4, figs. 4‒6.

Ophiosphalma variabile . Hendler 1996: 166, fig. 7.20c‒d.— Baker 2016: 37 , fig. 61a‒b.

Material examined. 10,938 individuals at eight stations. TALUD III, Sta. 6, 166 ind. (ICML-EMU-9016-A), 2 ind. (ICML-EMU-9016-B), and 3 ind. (ICML-EMU-11067-A). TALUD IV, Sta. 3, 2 ind. (ICML-EMU-11116). TALUD V, Sta. 3, 8 ind. (ICML-EMU-11067-B). TALUD IX, Sta. 10, 1 ind. (ICML-EMU-11068-B); Sta. 17, 1 ind. (ICML-EMU-11068-A). TALUD XV, Sta. 5D, 161 ind. (ICML-EMU-11070); Sta. 20, 20 ind. (ICML-EMU-11071), 4 ind. (ICML-EMU-11685), and 1 ind. (ICML-EMU-11948); Sta. 23, 1 ind. (ICML-EMU-11069-A), 43 ind. (ICML-EMU-11069-B), 5,862 ind. (ICML-EMU-11220), and 4,663 ind. (ICML-EMU-11221).

Comparative material. Ophiomusium variabile Lütken & Mortensen, 1899 , syntypes, 6 ind.: MCZ OPH-507 , USNM 19502 (Supplementary file 2).

Description (ICML-EMU-11220). DD = 12 mm. Whole-body with weakly tuberculous appearance. Disc pentagonal, flat. Dorsal disc covered with imbricated, irregular size scales. Primary plates not evident. RS longer than broad, oval, separated by several elongated scales; several elongated oval scales between each pair of RS, covering ½ of disc radius ( Fig. 3G ). Ventral interradii covered by oval imbricated scales, larger than dorsal scales. Genital slits with numerous minute quadrangular papillae ( Fig. 3H ). OSh longer than broad, rhombic with a distal lobe, right angles. Madreporite slightly larger than OSh. AdSh longer than broad, elongated, quadrangular, almost meeting or meeting in front of OSh. Jaws bearing 6‒7 oral papillae at each side, quadrangular, merging, two distalmost the largest; one pointed papilla at jaw tips ( Fig. 3I ). Arms thin, gradually narrowing distally. Dorsal arm base with 3‒4 overlapping DAP, several granules at edges of arm base, projecting ventrally. DAP slightly longer than broad, rhombic, separating and decreasing in size distally ( Fig. 3J ). First VAP smaller than rest; subsequent three VAP the largest (almost covering all arm segment length), separated from each other, the only ones with tentacle pores; posterior VAP triangular, reduced in size (approximately 1/3 LAP in length), separated from each other. First LAP with two ArSp, separated; subsequent LAP with three ArSp. Three tentacle pores with one rounded TSc covering pore almost completely ( Fig. 3K ). Color pattern beige-whitish (ethanol preservation) ( Fig. 3G‒L ).

Habitat and distribution. Mexican Pacific, from western Baja California Sur to Guerrero; 267‒ 1,148 m depth, muddy, sandy and rocky substrates (Lütken & Mortensen 1899; Maluf 1988; Granja-Fernández et al. 2015; see Remarks). The material examined was collected off western Baja California Sur, in the southern Gulf of California, and near Marias Islands; 530‒ 1,148 m depth.

Remarks. Ophiosphalma variabile is similar to O. jolliense in overall appearance. However, differences in their morphology (e.g., radial shields size and lateral arm plates shape) are provided by Hendler (1996). Moreover, they can be distinguished by: 1) the primary plates are clearly visible in O. jolliense vs. not so in O. variabile , and 2) spearhead-shaped with rounded edges oral shields in O. jolliense vs. rhombic-shaped with right angle oral shields in O. variabile . The previous northernmost distribution limit of O. variabile was in the Gulf of California (GranjaFernández et al. 2015). Its presence off western Baja California Sur, as reported herein, represents a new distribution record in the Mexican Pacific as well as a general distribution range extension to the north (to 27ºN). The deepest known record (i.e., 902 m; Maluf 1988) is extended to 1,148 m.

Figures

FIGURE 3. Ophiosphalma jolliense (McClendon, 1909) (ICML-EMU-11059-B, DD = 11 mm).A, Dorsal disc; B, Ventral disc; C, Mouth; D, Dorsal arm; E, Ventral arm; F, Dorsal view. Ophiosphalma variabile (Lütken & Mortensen, 1899) (ICML-EMU- 11220, DD = 12 mm). G, Dorsal disc; H, Ventral disc; I, Mouth; J, Dorsal arm; K, Ventral arm; L, Dorsal view.