Histampica duplicata

Histampica cf. duplicata (Lyman, 1875)

Fig. 18A‒F

Material examined. 31 individuals at five stations. TALUD XII, Sta. 8, 6 ind. (ICML-EMU-11705); Sta. 25, 1 ind. (ICML-EMU-11671); Sta. 27, 1 ind. (ICML-EMU-11715). TALUD XIV, Sta. 10, 8 ind. (ICML-EMU-12996). TALUD XV, Sta. 1, 15 ind. (ICML-EMU-11672).

Comparative material. Amphiura duplicata Lyman, 1875 (original name of Histampica duplicata (Lyman, 1875)), syntypes, 3 ind.: MCZ OPH- 1262, MCZ OPH- 1264, MCZ OPH- 4092 (Supplementary file 2).

Description (ICML-EMU-12996). DD = 5.4 mm. Disc slightly incised interradially. Dorsal disc covered by imbricated, depressed scales, no disc spines. Central primary plate round, surrounded by oval primary plates. RS scalene triangular, separated by three large scales (Fig. 18A). Ventral interradii covered by imbricated scales smaller than dorsal scales (Fig. 18B). OSh broader than long, spearhead-shaped with pronounced distal lobe. Madreporite slightly larger than OSh. AdSh trapezoidal, meeting in front of OSh. Jaws bearing four oral papillae at each side; AdShSp rounded; 2AdShSp quadrangular; BSc pointed; IPa pointed. vT quadrangular-rounded (Fig. 18C). Arms slender. DAP broader than long, triangular, twice as wide as long, distal edge convex, separated (Fig. 18D). VAP broader than long, pentagonal, separated. LAP with up to three ArSp, small (approximately one arm segment in length), blunt tip, dorsalmost the longest, ventralmost the shortest. Tentacle pores with two oval TSc (Fig. 18E). Color pattern dorsally and ventrally beige-whitish (ethanol preservation) (Fig. 18A‒F).

Habitat and distribution. The material examined is from western Baja California Sur, the Gulf of California, and off Colima and Guerrero; 325‒ 1,940 m depth, mostly on muddy bottom.

Remarks. Histampica duplicata is known from the Gulf of Vizcaya to South Africa, the North Atlantic, the Gulf of Mexico, the Caribbean, Barbados, and Brazil, and also in the eastern Pacific (Lyman 1875; Lütken & Mortensen 1899; H.L. Clark 1917; Paterson 1985; Granja-Fernández et al. 2015; Stöhr et al. 2022). The first record in the eastern Pacific was by Lütken & Mortensen (1899), who observed morphological differences between their specimens from Malpelo and Galapagos Islands and the type material from Barbados. We also observed differences in the Mexican Pacific morphology comparatively with the type material, including 1) very well-formed and conspicuous rosette of primary plates in H. duplicata, 2) smaller radial shields in H. duplicata, and 3) spearheadshaped oral shields without a distal lobe in H. duplicata. The above differences may be due to the specimens’ size or to a variation due to regional environmental conditions. The Mexican-eastern Pacific morphology may represent another species, but detailed morphological and molecular analyses are needed to confirm this.