Hippasteria undetermined

Mah, Christopher, Neill, Kate, Eléaume, Marc & Foltz, David, 2014, New species and global revision of Hippasteria (Hippasterinae: Goniasteridae; Asteroidea; Echinodermata), Zoological Journal of the Linnean Society 171 (2), pp. 422-456 : 436-438

HIPPASTERIA MCKNIGHTI SP. NOV.

( FIG. 5A–F )

Etymology

This species is named after the late Don McKnight (1936–2012), former echinoderm researcher at the New Zealand Institute of Water and Atmospheric Research who greatly contributed to our understanding of asteroid biodiversity in New Zealand waters.

Type species

Hippasteria mcknighti sp. nov., holotype NIWA 66853 .

Comments

Hippasteria mcknighti sp. nov. is shown as the sister taxon to H. heathi clade in Figure 1 but this relationship is poorly supported and requires further investigation. However, the morphology of H. mcknighti does closely resemble that of H. heathi , differing primarily in abactinal, marginal, and actinal spine shape and in having a more stellate body form.

Occurrence

New Zealand region. 720–1015 m.

Description

Body stellate (R: r = 1.85–2.27), disk tumescent, confluent with triangular arms.

Abactinal surface ornamentation is primarily composed of widely spaced tubercles and pedicellariae, large and homogenously sized, cover abactinal surface ( Fig. 5A, B ). Pedicellariae and tubercles flanked by four to six papular pores, present on fasciolar surface (between spine and pedicellariae bases). Tubercles, smooth, thickened, short, and tubercular; sit on bases surrounded by distinct, wide fasciolar grooves. Each tubercular base distinct with two to 15 small round to polygonal accessory granules forming irregular fringe around each spine. Other secondary underdeveloped tubercles or irregular spines also present on smaller bases present irregularly over surface. Large bivalve pedicellariae (most approximately 1.0–2.0 mm in length) cover most of abactinal surface between tubercles (spines). One to two pedicellariae present between tubercles. Pedicellariae valves smooth with no teeth. Similar to the tubercles, pedicellariae sit on elevated bases covered by small, irregularly shaped granules ( Fig. 5B ). Fasciolar surfaces (lower regions between spines and pedicellariae bases) covered by a thickened epidermis. Some smaller accessory granules and/or underdeveloped smaller tubercles present amongst fasciolar surface. Madreporite pentagonal, recessed, flanked by approximately five to seven abactinal plates ( Fig. 5B ). Sulci well defined, arranged in a maze-like pattern.

Marginal plates 40 per inter-radius (at R = 6.1 to 7.5), quadrate in shape. Each plate has one to five large, but squat, cone-shaped tubercles and one to two (most have one) large bivalve pedicellariae on plate surface. Number of tubercles, pedicellariae, and other accessories is highest inter-radially, decreasing distally. Pedicellariae largest and most numerous interradially, becoming smaller and eventually absent on distal-most marginal plates. Pedicellariae with smooth valves, no teeth, similar to those on abactinal and actinal surfaces. Marginal plate periphery covered by 18–35 differently sized and irregularly shaped granules. Accessory granules are most strongly heterogeneous interradially with most disparity in size and shape, interradially becoming more homogeneous and evenly sized around marginal plates distally. Large inter-radial granules on both marginal plate series are in some cases approximately five to ten times the size of adjacent granules and quadrate to polygonal in outline. Superomarginals with only one to two tubercles and with some bare surface present. Inferomarginals with one to five tubercles. Inferomarginal plate surface covered with five to 15 coarse, polygonal but unevenly sized granules covering plate surface. Inferomarginal plate covering is more contiguous with actinal plate granular covering with polygonal granules and tubercles spilling over onto marginal plate series from actinal intermediate region. A distinct fasciolar groove is present amongst marginal plate series. Terminal plate triangular in shape, similar in size to adjacent distalmost superomarginal plate.

Actinal region composed of plates arranged in six to seven crowded chevron-like series ( Fig. 5B ). Ornamentation and accessories similar to those on abactinal and marginal surfaces − with plates covered by large, squat tubercles and large-sized bivalve pedicellariae (1–2 mm in length; Fig. 5B, E ). Pedicellariae identical to those on other surfaces with smooth valves, no teeth and are most abundant proximally becoming less numerous adjacent to contact with inferomarginals. Tubercles, large, ranging from round to polygonal in cross-section, are more abundant and are more densely distributed on distal-most regions adjacent to inferomarginal plates and along arms approaching arm-tips. Pedicellariae are present on nearly every actinal intermediate plate but are largest in size and observed most clearly on the actinal plate series adjacent to the adambulacral plates. Pedicellariae become smaller more distally. As with the abactinal surface, both tubercles and pedicellariae sit on basal plate with five to 12 peripheral granules (mostly seven to nine). Similar to others, granules are heterogeneous in size and shape with small accessory gran- ules sitting adjacent to larger granules five to ten times in size and differing in shape (quadrate to round and nearly tubercle-like). Larger, more heterogeneous granules appear to be more common on plates with pedicellariae, whereas smaller, more homogenous ones appear to be present more commonly on those with tubercles. A prominent fasciolar groove is present between all actinal and marginal plates. Papulae absent from actinal surface.

Furrow spines, blunt, two to three (mostly two) per plate, each spine flattened and oval-shaped in crosssection ( Fig. 5E, F ). Subambulacral spines, blunt, one to three, in transverse series, often thick and triangular to quadrate in cross-section thicker than furrow spines but about 80–90% of furrow-spine length. Adambulacral plate elongate with short (25% of furrow spine height), laterally flattened, blade-like spinelets, three to five in number on side adjacent to actinal plates. Oral plates with five to seven flattened, blade-shaped furrow spines. Oral plate surface each with three to seven short spinelets, triangular to polygonal in crosssection ( Fig. 5F ). Some inter-radii with more welldeveloped epidermis.

Colour in life is orange.

Material examined

Holotype. NIWA 66853 , off New Zealand, 48.371°S, 175.285°E to 48.33°S, 175.292°E, 907–1015 m. 12.x.2006. Coll. Scientific Observer Program. TRIP 2324 /152 (one dry spec. R = ∼7.5, r = 3.3, arms upturned) . Paratype. NIWA 44152 , off New Zealand, 47.47°S, 177.02°E, 47.47°S, 177.027°E, 720–741 m. 28.iv.2007. Coll. Scientific Observer Program. TRIP 2416 /54. (one dry spec. R = 6.1, r = 3.3, arms upturned) .

Figures

Figure 1. Evolutionary relationships of sampled Hippasterinae (Goniasteridae) based on 654 aligned nucleotide positions of the cytochrome c oxidase subunit I gene. The phylogenetic tree was inferred using the neighbour-joining method (Saitou & Nei, 1987) in MEGA v. 5.2.1 (Tamura et al., 2011). The bootstrap consensus tree inferred from 500 replicates was drawn to scale, with distances computed using the maximum composite likelihood method (Tamura et al., 2004), in units of numbers of base substitutions per site. Ambiguous positions were removed for each pair of sequences prior to calculating the distance matrix. Terminals were labelled with GenBank accession numbers and (where available) with museum voucher numbers. Bootstrap support values are shown above or below branches when greater than 70%.

Figure 5. Hippasteria mcknighti sp. nov. NIWA 66853. Scale bar = 1.0 cm for all unless otherwise specified. Paratype. A, abactinal surface. B, actinal surface. C, close-up of abactinal surface showing spines, pedicellariae, and madreporite. D, marginal plate series. E, actinal surface showing furrow spines, actinal spines, and pedicellariae. F, actinal surface over mouth region, showing oral spines, actinal surface with pedicellariae, and spination.