Ophioderma peruana Pineda-Enriquez , Solis-Marin , Hooker & Laguarda-Figueras

Pineda-Enriquez, Tania, Solis-Marin, Francisco A., Hooker, Yuri & Alfredo Laguarda-Figueras,, 2013, Ophioderma peruana, a new species of brittlestar (Echinodermata, Ophiuroidea, Ophiodermatidae) from the Peruvian coast, ZooKeys 357, pp. 53-65 : 55-58

Ophioderma peruana Pineda-Enriquez, Solis-Marin, Hooker & Laguarda-Figueras sp. n.

Type specimen.

Holotype, CZA-363, Lobos de Afuera Island, Peru, 6°56'16.8"S, 80°43'22.7"W, intertidal, under rocks, October 9th, 2007.

Type locality.

Peru: Lobos de Afuera Island, 6°56'16.8"S, 80°43'22.7"W, intertidal, under rocks, October 9th, 2007.

Other type material.

Paratype, CZA-364, Lobos de Afuera Island, Peru, 6°56'16.8"S, 80°43'22.7"W, intertidal, October 9th, 2007; paratype, CZA-365, Lobos de Afuera Island, Peru, 6°56'16.8"S, 80°43'22.7"W, intertidal, October 9th, 2007; paratype, UNAM-ICML 3.234.0, Lobos de Afuera Island, Peru, 6°56'16.8"S, 80°43'22.7"W, intertidal, under rocks, October 9th, 2007 (Fig. 2).

Diagnosis.

Disc pentagonal, elevated and covered with dense granules that are somewhat rounded or polygonal, but more or less dispersed. The radial shields can be completely covered by the granules or scarcely covered. The dorsal arm plates are fragmented; in addition there are some smaller and tiny fragments that resembles granules of the dorsal disc, only visible on the proximal plates (not evident in all the arm segments). Nine or ten flattened and elongated oral papillae. Granules also cover the adoral shields. Ten arm spines, the ventral is the largest, reaching the next tentacle scale.

Description of holotype.

CZA-363: disc diameter 36.3 mm, arm length 120.6 mm, arm width 7.6 mm (Fig. 2).

Disc. Disc pentagonal, broad and flat, covered by granules; the dorsal granules are closely packed and have the same size on the middle and periphery of the disc, these granules are rounded and polygonal. The radial shields are almost fully covered by granules with only a small section exposed; the size is 3.81 mm and fit 9.5 times the disc diameter; the disc scales are small and imbricated, oval shape with polygonal borders, the interradial scales are smaller than the radial ones. Jaws with seven to nine oral papillae; the two distal ones are stout and longer than broad. The oral papillae have rounded edges and are almost of the same size and shape. The oral shields are broader than long, triangular in shape with convex proximal sides and are surrounded by granules that are slightly larger than those on the interradial disc surface. The adoral shields are rectangular and covered by larger and taller granules than those on the dorsal disc, which are contiguous. Four genital slits on each interradii; the two proximal ones are touching the oral shield and are located between the distal part of the oral shields and the first lateral arm plate; the two distal genital slits are placed between the fifth and and the sixth arm segment and close to the periphery of the disc.

Arms. The basal portion of the arm is 7.6 mm broad and the arm length is 120.6 mm. The dorsal arm plates occupy less than 1/4 of the arm, are 4.6 times wider than long and rectangular, fragmented in six pieces that differ in shape; there are some granules on the proximal portion and sparcely distributed on the distal portion. The lateral arm plates have a half-circle shape, and occupy a sub-ventral position; with ten arm spines conical, large and slightly flattened with a rounded tip, half segment length decreasing slightly in size dorsally. The ventral-most arm spine is the longest and widest, almost the size of the segment. The ventral arm plates are contiguous, broader than long, the proximal plates are elongated in comparison to the distal plates. Two tentacle scales on each side of the ventral plate; the adradial tentacle scale is oval in shape, twice as long as wide and the abradial tentacle scale triangular in shape, with the straight side touching the ventral arm plate (Fig. 3).

Color. Specimen preserved in alcohol. The dorsal side of the disc is light brown and the arms are darker brown, the dorsal arm plates of each segment are ornamented with a double row of tiny, whitish, rounded spots; the spines are brown except the two ventral ones that are cream color, like the ventral side of the arms; the jaws are white; the ventral side of the disc in the proximal part is white and the distal part is slightly darker; the oral shields are mottled. Dry specimens, have the dorsal side of the disc pale brown, the arms are brown with black and white spots; the tentacle feet are yellowish. Live specimens in the field could be identified by this color pattern: the dorsal side of the disc is brown with the disc granules lighter cream and brown; the arms are mottled with whitish spots; the ventral disc interradii are brown and arms under the disc are bright yellow.

Paratype variations. Onthe smallest specimen (14 mm DD; 35 mm AL; 4 mm AW) the radial shields are completely naked with white spots (same color pattern as the dorsal arm plates), oval and surrounded by the disc granules by the disc granules, scarcely covered (in specimens with 40-42 mm DD) or completely naked (in specimens with14-35 mm DD). On certain segments of the arm, the dorsal arm plates are not as fragmented, with only two or three pieces. The presence of granules along the arm is not evident as in the holotype. In some specimens (22-31 mm DD) the radial shields are also completely naked. The oral shields are twice as wide as long, proximally elongated but the shape may vary in specimens. In two specimens (30 mm; 42 mm DD) the radial shields are naked and/or covered by granules. The radial shields are completely covered by granules and dorsal arm plates are fragmented in only a single specimen (35 mm DD) (Fig. 4). Therefore, as the animal grows, the radial shields become more covered in granules and the dorsal arm plates are fragment further.

Distribution.

Only known from the coast of Peru. Lobos de Afuera Island, Lambayeque, Peru; intertidal (type locality); Quebrada Verde, El Ñuro, Peru, 9 m; 4°13'39.3"S, 81°12'30.0"W and Hooker Reef, Punta Sal, Peru; 14 m; 3°57'14.20"S, 80°57'48.50"W (Fig. 1).

Etymology.

Named after the type locality.

Remarks.

The new species is distinguishable by its thick and rounded granules on the disc, the number of fragments of the dorsal arm plates, which can be more than six with other smaller fragments. The distal border of the dorsal arm plates, from the base to the middle part of the arm, supports some granules similar to those on the dorsal part of the disc.

In Peruvian waters, Ophioderma panamensis and Ophioderma teres are found on the same localities, in addition tothe new species; it differs from other Peruvian species in shape and size of the tentacle scales and in the shape of the arm spines. It differs from Ophioderma teres by the smaller size and density of the granules on the disc. These granules are similar to those present on Ophioderma sodipallaresi , the main difference is that on the latter species they are somewhat more scattered than in Ophioderma teres , while in Ophioderma peruana sp. n. the dorsal granules are closely packed and have the same size on the middle and periphery of the disc, being rounded and polygonal. Ophioderma sodipallaresi differs in havingonly two to three fragments, whereas Ophioderma teres have a similar number to Ophioderma peruana sp. n. The shape and size of the tentacle scales in Ophioderma teres are similar to Ophioderma peruana sp. n., oval and elongated, whereas in Ophioderma sodipallaresi the abradial tentacle scale is longer than wide and the adradial scale is smaller, almost triangular or oval. The ventralmost arm spines are largest in all three species, and the others increase in size from dorsal to ventral. In Ophioderma peruana sp. n. the arm spines are thick and conical, similar to Ophioderma sodipallaresi , which are pointed, thick and short, but differing in size. Meanwhile, in Ophioderma teres the arm spines are almost flat with pointed tips. In comparison with the other West Pacific ophiodermatids species, Ophioderma panamensis and Ophioderma vansyoci differs from Ophioderma peruana sp. n. by presenting the radial shields naked, just bordered by the granulation of the disc; in contrast with Ophioderma variegata and Ophioderma pentacantha that has the radial shields covered by the disc granules, while in Ophioderma peruana sp. n. the radial shields could be naked or covered by the granules. Ophioderma vansyoci presents the dorsal arm plates fragmented in three pieces. The number of arm spines are variable, Ophioderma pentacantha has five, Ophioderma vansyoci has seven, Ophioderma panamensis and Ophioderma variegata has eight, while Ophioderma peruana sp. n. presents ten, Ophioderma sodipallaresi seven arm spines and Ophioderma teres nine arm spines. Ophioderma variegata and Ophioderma pentacantha presents the adoral shields slightly naked, in comparison with Ophioderma panamensis , Ophioderma vansyoci , Ophioderma sodipallaresi , Ophioderma teres and Ophioderma peruana sp. n. that presents the adoral shields covered by the disc granules. Among its congeners in the Caribbean Sea, Ophioderma peruana sp. n. is more similar to Ophioderma squamosissima and Ophioderma guttata sharing fragmented dorsal arm plates (more than six pieces) but differs from the later ones in the absence of the smaller scales on the dorsal arm plates, by having different shape of disc granules (rounded and polygonal in Ophioderma peruana sp. n., flattened, elongated and polygonal shape in Ophioderma squamosissima and flattened, shorter and polygonal in Ophioderma guttata ), in addition to its geographic distribution. The rest of the Ophioderma species distributed in the Caribbean Sea either lacks fragmented arm plates ( Ophioderma appressa , Ophioderma brevicauda , Ophioderma brevispina , Ophioderma phoenium and Ophioderma rubicunda ) or some segments of the dorsal arm plates could be fragmented ( Ophioderma cinerea ).