Evoplosoma voratus, Mah & Nizinski & Lundsten, 2010

Mah, Christopher, Nizinski, Martha & Lundsten, Lonny, 2010, Phylogenetic revision of the Hippasterinae (Goniasteridae; Asteroidea): systematics of deep sea corallivores, including one new genus and three new species, Zoological Journal of the Linnean Society 160 (2), pp. 266-301 : 279-280

EVOPLOSOMA VORATUS SP. NOV.

FIGURE 8A–E

Occurrence: Known from Davidson Seamount, 2669.9 m.

Material examined: HOLOTYPE: USNM 1124506 , Davidson Seamount, 35°37′N, 122°49′W, 2669.9 m, coll. J. Barry, L. Lundsten, Sta. T-947-A10, 2.ii.2006 (1 wet spec. R = 8.4, r = 2.7).

Etymology: The epithet for this species refers to the Latin voratus which means to ‘greedily devour’ in reference to its observed feeding habits on deep-sea coral.

Description: Arms tapering, slender but gradually extending from disk. Disk, swollen more pentagonal with relatively lateral to curved inter-radial arcs.

Abactinal surface with weakly developed pulpy surface with abactinal surface on arms appearing more pulpy. Abactinal plates round to polygonal becoming smaller and less round distally near contact with superomarginal plate series but larger distally, especially on arms. One to four plates across distance of arm between superomarginal plate series. Abactinal plate surfaces mostly bare with short, stubby conical tubercles. Plates with tubercles not very abundant, only about four to six per arm base on disk. Each plate with ten to 30 peripheral rounded granules that are small and rounded to quadrate in crosssection. Region adjacent to madreporite (about 0.75 ¥ 1.0 cm area) covered with densely packed, large, round granules about twice the size of granules on the abactinal surface and embedded in the pulpy tissue present on the body wall. Madreporite is ovalshaped with deeply etched sulci. Peripheral granules surround madreporite with some granules two to three times as large as others. One plate with two to four large granules on one end of madreporite. Paddle-shaped pedicellariae uncommonly scattered over surface, approximately one or two for every five to seven plates.

Marginal plates, bare with a single large, conical spine on most plates, arranged in linear series becoming smaller to absent on distalmost six or nine superomarginal plates. Several spines, especially along the arms, with four to six short, spiny granules at the base of each spine that are absent distally. Spines continue along all inferomarginal plates up to practically the terminal plate. Both marginal plate series covered by skin, which is difficult to observe in dry specimens. Pedicellariae small, tong-like present irregularly on superomarginals and inferomarginals, especially inter-radially. Peripheral granules rounded, 40–60 per plate, including ~ten per side adjacent to other marginal plate and ~25 per side adjacent to abactinal and actinal surface. Superomarginal and inferomarginal offset from one another and each series with different overall dimensions. Superomarginals number 44–45 from armtip to armtip, more elongate (L> W), becoming almost ovalate. Inferomarginals number 54–55 from armtip to armtip, more quadrate (L = W) overall. Superomarginal plate contact with abactinal surface, strongly convex, ovallike especially along the base and along the arm. Inferomarginal with more gently curved contact with actinal intermediate plates.

Actinal intermediate plates in approximately three to four chevron-like patterns but in very jumbled, irregular, unclear series present only on disk, ending at arm base. Plates quadrate to irregular in shape and bare with no spination or surface accessories with eight to 25 peripheral granules save for irregularly occurring paddle-like pedicellariae. Pedicellariae, one to six, present in actinal intermediate region.

Adambulacral plates elongate, with typically one (exceptionally two) large paddle-like to rectangular pedicellariae sitting on plate always closest to mouth adjacent to enlarged, thickened subambulacral spine that sits distal to mouth. Approximately six to eight large granules on periphery of adambulacral plates in contact with actinal intermediate plates. Subambulacral spines up to two to three times the thickness of furrow spines with blunt to conical tips. Pedicellariae begin to occur on first adambulacral, becoming less regular on distal adambulacral plates. Furrow spines, compressed, quadrate to oval in cross-section, four to six in number, five on average, with middle spines tallest, shortest spines on the ends. Furrow spine tips darkened brown sometimes roughened and jagged. First adambulacral with six to seven furrow spines, significantly thicker with more jagged tips than other furrow spines.

Oral region concave with approximately 13–15 compressed furrow spines on each oral plate. Furrow spines, flattened and blade-like, one to two present at plate apex, the largest of which pairs off with its twin on the other oral plate and forms a closely articulated array of spines over the mouth. Oral plate surfaces appear bare save for soft, pulpy tissue covering approximately eight to 12 plates through which two to four short granules emerge.

Colour in life of the holotype was deep-brick red, which remained almost two weeks following preservation in 75% ethanol.

Observed in situ apparently feeding on Trissopathes pseudotristicha ( Cladopathidae , Antipatharia ).

Figures

Figure 8. Evoplosoma voratus sp. nov. USNM 1124506. A, abactinal surface; B, close-up of abactinal plates and madreporite; C, lateral view of marginal plates; D, oral surface; E, close-up of furrow spines an adambulacral armature; F, in situ video of E. voratus feeding on Trissopathes pseudotristicha on Davidson Seamount. Two circular dots (lights) are 29 cm. Scale bars: A, B, D, E = 3 mm; C = 6 mm.