Hippasteria, LEPIDONOTUS (FISHER, 1905)

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 : 434-435

HIPPASTERIA LEPIDONOTUS ( FISHER, 1905)

Ludwig, 1905: 138 (as Hippasteria pacifica ).

Fisher, 1905: 311; 1911: 237; Lambert, 1978a: 9; Maluf, 1988: 34, 118; A.M. Clark, 1993: 251; Mah et al., 2010; Hendrickx et al., 2011: 800 (as C. lepidonotus ).

Codoceo & Andrade, 1981: 379 (as Ciyptopeltaster philippii).

Pawson & Ahearn, 2001: 42 (as Cryptopeltaster cf. lepidonotus ).

Type species

Cryptopeltaster lepidonotus Fisher, 1905 . Holotype USNM 22340, lost as per Mah et al. (2010). Replaced by neotype E33356 (see Mah et al., 2010).

Comments

Our CO1 data supported C. lepidonotus amongst other species in the genus Hippasteria with 93% bootstrap support, strongly supporting the synonymy of Cryptopeltaster Fisher, 1905 within Hippasteria Gray, 1840 . In addition to the COI evidence, morphological evidence is also consistent with this hypothesis, especially when considered within a phylogenetic context.

Fisher (1905, 1911) differentiated Cryptopeltaster based on three characters, granulation morphology, arrangement of the abactinal secondary plates, and the substitution of a large bivalve pedicellaria for the furrow spines on some of the adambulacrals. Mah et al. (2010) analysed characters amongst hippasterines and outlined character autapomorphies for Cryptopeltaster . The position of Cryptopeltaster in Figure 1 differs substantially from its place in the tree of Mah et al. (2010), which placed it as the sister taxon to Gilbertaster on a sister branch to Hippasteria , Evoplosoma , and Sthenaster .

Within the context of our data ( Fig. 1 ), diagnostic characters for Cryptopeltaster from Fisher (1911) and Mah et al. (2010) are re-interpreted as autapomorphies within Hippasteria rather than synapomorphies. This is consistent with an interpretation of characters such as abactinal plate morphology, spines, pedicellariae, and granules as evolutionarily labile and subject to environmentally induced homeomorphy and selective ecological pressures (e.g. Blake & Kues, 2002). The distinctive granules, secondary plates, and pedicellariae could all be interpreted as defensive structures and could be significant in protection against predators. Mah et al. (2010) also indicated predation by Cryptopeltaster on the sea whip, Halipteris . Characters such as spination and heavy armour may defend against antipredatory cnidoblasts produced by prey species. Several characters, such as low furrow spine number, spines present on marginal plates, and prominent abactinal and actinal spines, used to distinguish Cryptopeltaster by Mah et al. (2010) would be interpreted as plesiomorphic within our tree. Several characters outlined in Mah et al. (2010), such as overall body thickness, arm shape, low furrow spine number, and pedicellariae morphology, to diagnose Hippasteria are shared with Cryptopeltaster , further supporting synonymy of the genus.

Occurrence

Chile, Galapagos Islands, to Aleutian Islands (Alaska), including records from Rodriguez Seamount, Santa Cruz, California, and British Columbia 188–1244 m.

Description (as per Mah et al., 2010)

R: r = 2.3–2.6, arms triangular, disk broad.

Abactinal surface covered by large, coarse, flat, angular granules, densely abutting around spines and pedicellariae. Abactinal plates largest proximally, becoming smaller distally adjacent to contact with superomarginal plate series. Spines conical, present, large, numerous on abactinal surface with granules forming flattened, angular skirt around each spine base. Spines or pointed granules present on nearly every abactinal plate, especially those on radial regions, but nearly absent distally on regions adjacent to superomarginal series. Pedicellariae large (length equivalent to about seven to nine granules), bivalved. Secondary plates, when present covered by one or two granules.

Marginal plates, 40–55 per inter-radius (from terminal to terminal), each covered with granules, densely arranged, polygonal, quadrate to angular in shape. Number of marginal plates increases as adult size increases. Granules number 20–30 around each marginal plate periphery, forming convex contact with abactinal and actinal surfaces. Granules on central marginal plate surfaces number 20–40. Granules, smooth, angular in outline, flattened to convex, and often with a pointed tip, distributed evenly throughout surface. Spines, one to three (typically one), short, conical to tubercular, present at lower end of each superomarginal plate adjacent to contact with inferomarginal plates. Spines present on inferomarginals inter-radially, becoming lower and more tubercular distally along arms. Granules becoming more level with other granules distally on arms.

Actinal intermediate areas covered with similar flattened, closely abutting, angular granules, almost all with spines or tubercles. Spines, conical, single and prominent, on each actinal intermediate plate are most abundant proximally, adjacent to the mouth. Spines, smaller and disappearing distally (adjacent to inferomarginal plate contact). Large bivalve pedicellariae (length about 3.0 mm each) in a distinct linear series adjacent to adambulacral plate series, each surround- ed by 11–15 angular granules. Approximately five to seven chevrons of actinal plates per inter-radius.

Adambulacral plates primarily occupied by two to three (primarily three) furrow spines per plate, but a large bivalve or trivalve pedicellariae will replace these spines on the first postoral adambulacral plate and irregularly if infrequently on the furrow spines. Furrow spines thick, club-shaped, and round in cross-section. Each paired oral plate with six to eight angular granules along median axis but with four to six granules covering remaining oral plate surface. Furrow spines, three to four on each oral plate. Spine, thickened, oblong in cross-section on the surface of each oral plate facing into the mouth.

Material examined

CASIZ 108628 , Monterey , CA, off Point Sur, 914.0 m (500 fms), coll. M. Eric Anderson, 7.vi.1977 (one wet spec. R = 4.4; r = 1.7) ; CASIZ 11828 , Oregon, off the coast, 47°15.68′N, 124°53.4′W, 188–216 m, coll. Roger N. Clark aboard R V Miller Freeman, 22.x.1996 (one dry spec. R = 13.1 r = 5.2) ; USNM 1129943 , Rodriguez Seamount , 34°2′49.2″N, 121°4′4.8″W, 667.3 m, coll. D. Clague, on board R V Tiburon, 29.iv.2004 (one wet spec. R = 9.6, r = 6.1) ; USNM E47396 , Washington, north-west of Grays Harbor , 47°10.37′N, 124°57.58′W, 195–242 m, coll . R. N. Clark on board R V Miller Freeman, 22.x.1996 (two dry specs R = 9.8, r = 3.8; R = 10.8, r = 4.8) ; USNM E51296 , north of Seymour Island, Galapagos Islands , 00°21′42″S, 90°15′00″W, 599 m (1964 ft), coll. C. Baldwin & J. McCosker, Johnson Sea Link II, 26.vii.1998 (one wet spec. R = 8.1, r = 3.5) .

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%.