Amphiura arcystata 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 : 47-48

Amphiura arcystata H.L. Clark, 1911

Fig. 14A‒F

Amphiura acrystata H.L. Clark, 1911: 145‒148 , fig. 58 (lapsus calamus for arcystata )

Amphiura arcystata . H.L. Clark 1915: 224; 1940: 336; 1970: 10‒11.— Nielsen 1932: 264.— Ziesenhenne 1937: 223.— Boolotian & Leighton 1966: 4, 8, fig. 7.— Hendler 1996: 145‒147.

Hemilepis arcystata . Fell 1962: 10, 19.

See Hendler (1996) for other synonymous records.

Material examined. One individual at one station. TALUD XV, Sta. 23, 1 ind. (ICML-EMU-12995).

Comparative material. Holotype: USNM 25623 . Paratypes, 53 ind.: MCZ OPH-3135 , MCZ OPH-3136 , MCZ OPH-3137 , MCZ OPH-3138 , MCZ OPH-3368 , MCZ OPH-3369 , USNM 25834 , USNM 25837 , USNM 26078 , USNM 26130 , USNM 26188 , USNM 26197 , USNM 26609 , USNM 27094 , USNM 27124 , USNM 33638 (Supplementary file 2) .

Description (ICML-EMU-12995). DD = 5.3 mm. Disc strongly shrinked due to preservation. Dorsal disc covered mostly by integument, imbricated scales around RS. Primary plates not evident. RS very conspicuous, thicker distally, in contact only distally, the rest separated by scales ( Fig. 14A ). Ventral interradii covered by scaleless integument ( Fig. 14B ). OSh broader than long, oval, with distal lobe. Madreporite larger than OSh. AdSh triangular, separated interradially and radially. Jaws bearing three oral papillae at each side; AdShSp elongated when present; BSc elongated, pointed; IPa rounded. vT quadrangular ( Fig. 14C ). Arms slender, elongated. DAP broader than long, oval, meeting ( Fig. 14D ). VAP a little broader than long, almost quadrangular, meeting. LAP with five ArSp, small (approximately one arm segment in length), pointed, ventralmost the longest and dorsalmost the shortest. Tentacle pores with two oval TSc ( Fig. 14E ). Color pattern in dorsal and ventral disc and arms beigewhitish (ethanol preservation) ( Fig. 14A‒F ).

Habitat and distribution. Japan, California, USA, Mexico, Costa Rica, Colombia, and the Galapagos Islands (H.L. Clark 1911; Maluf & Brusca 2005); 60‒848 m depth, muddy and sandy substrates (H.L. Clark 1911; Ziesenhenne 1937; Hendler 1996). The material examined was collected off western Baja California Sur; 625 m depth.

Remarks. During the TALUD cruises, only one specimen of Amphiura arcystata was collected and it is smaller than the holotype (USNM 25623, DD = 10 mm). The specimen differs in the number of arm spines (5 vs. 6‒7 in the holotype) and the thickness of the radial shields (thicker in the smaller specimen). Juvenile or small individuals of A. arcystata are known to significantly differ morphologically from adults, and it has been recorded that this species shows a great morphological variability regardless of size (H.L. Clark 1911; Hendler 1996). In this respect, the revision of the type material evidenced two morphologies (one from Japan ‒USNM 26130, MCZ OPH-3137 and the other from California‒USNM 25623, MCZ OPH-3135, MCZ OPH-3369) featuring differences in the presenceabsence of scales and integument in dorsal disc, the shape of the radial shields, oral shields, dorsal arm plates, ventral arm plates, and arm spines. The unique specimen collected during this survey agrees with the holotype from California. Japan and California morphologies probably correspond to different species, but more morphological and molecular evidence is needed. Due to the significant morphological variability observed here, we recommend reviewing the material of A. arcystata from Central and South America ( Costa Rica, Colombia, and the Galapagos Islands). In Mexico, it has previously been collected off western Baja California, in the Gulf of California, and off Guerrero ( Granja-Fernández et al. 2015). The current record is a first for the west coast of Baja California Sur.

Figures

FIGURE 14. Amphiura arcystata H.L. Clark, 1911 (ICML-EMU-12995, DD = 5.3 mm). A, Dorsal disc; B, Ventral disc; C, Mouth; D, Dorsal arm; E, Ventral arm; F, Dorsal view. Amphiura carchara H.L. Clark, 1911 (ICML-EMU-11667, DD = 7 mm). G, Dorsal disc; H, Ventral disc; I, Mouth; J, Dorsal arm; K, Ventral arm; L, Dorsal view.