Odontaster meridionalis

Odontaster meridionalis (Smith, 1876)

FIGURE 13A–E

Astrogonium meridionalis Smith, 1876: 109.

Pentagonaster meridionalis Smith 1879: 276.

Gnathaster meridionalis Sladen 1889: 287.

Odontaster meridionalis Fisher 1940: 99; A.M. Clark 1962: 15; H.E.S. Clark 1963: 34; Guille 1974: 32.

Diagnosis

Body weakly stellate to stellate, R/r=1.6–2.25. Disk broad, arms triangular. Interradial arcs weakly curved to straight (Fig. 13A, C). Fasciolar groove present between abactinal, marginal, actinal plates, well-developed. Abactinal surface covered by paxillate plates (Fig. 13B). Plate bases quadrilobate. Plates arranged in serial rows along arm, extending to arm tip. Each plate with spinelets, 12–25 per plate, spinelets, each with a pointed tip, spinelets largest centrally on paxillar surface. Marginal plates wide 20–28, arm tip to arm tip, quadrate, in shape, covered by 20–30 spinelets, widely spaced (Fig. 13A). Actinal plates in 5–7 chevron-like series, each plate quadrate in shape, covered by spinelets, rough, “thorny” tipped (Fig. 13D). Furrow spines pointed, 3–4 in straight series with median spines tallest, subambulacral spines 7–9 arranged irregularly (Fig. 13E). Oral plates each with a single distinct recurved hyaline tipped spine, furrow spines 6–8, suboral spines 5–6.

Comments

These records show further occurrence of a species known previously from relatively shallow settings (<646 m) extending into the bathyal and abyssal zones (1772–2907 m). Examination of specimens revealed only minimal morphological variation from the Ross Sea region of the Southern Ocean occupying shallower habitats. The abactinal and marginal paxillar spines appeared to have slightly more robust club-shaped tips on deeper-water deep-water individuals from the Ross Sea area (2273 m) than those on shallow-water specimens (64 m) from the Antarctic Peninsular region that also have had less well-developed paxillar spines. However, in other respects, specimens appear similar (e.g., A.M. Clark 1962).

Occurrence

Circumpolar, including South Georgia, Marion Island, 0–646 m (following A.M. Clark 1962). New Depth Occurrence: 1772–2907 m.

USNM 1083015, Ross Sea, Southern Ocean, −75.817, −168.867, 2049–2089 m. Coll, R/V Eltanin, 3 Feb. 1968. 1 dry spec. R=2.1 r=1.1.

USNM 1091164, Victoria Land, Southern Ocean, −72.442, 177.133, 1883–1890 m. Coll. R/V Eltanin, 12 Feb. 1968. 1 dry spec. R=1.6 r=0.9, R=1.5 r=0.8, R=1.1 r=0.6.

USNM 1091165, Victoria Land, Ross Sea, Southern Ocean, −72.958, 174.408, 1772–1775 m. Coll. R/V Eltanin, 11 Jan. 1968. 1 dry spec. R=1.9 r=0.9.

USNM 1091167, Southern Ocean, −73.317, −174.875, 2897–2907 m. Coll. R/V Eltanin, 9 Feb. 1968. 7 dry specs. R=2.2 r=1.1, R=1.8 r=0.9, R=2.0 r=0.9, R=1.6 r=0.7, R=1.4 r=0.7, R=1.0 r=0.6, R=1.2 r=0.6.

USNM 1091180, Southern Ocean, −74.933, −174.233, 2022–2060 m. Coll. R/V Eltanin, 7 Feb. 1968. 2 dry specs. R=2.2 r=1.2, R=2.4 r=1.3.

USNM 1121140, Victoria Land, Ross Sea, Southern Ocean, −70.917, 171.992, 2273 m. Coll. R/V Eltanin, 13 Jan. 1967. 1 dry spec. R=2.0 r=1.1.

USNM 1123078, Ross Sea, Southern Ocean, −74.875, −174.933, 2143–2154 m. Coll. R/V Eltanin, 27 Jan. 1967. 1 dry spec. R=7.4 r=3.7.

NHM-BAS specimen 1, Scotia Sea, −60.0459333, −29.97751667, 2397 m. Coll. British Antarctic Survey. 1 wet spec. R=3.7 r=1.7.

NHM-BAS specimen 2, Kemp Seamount caldera, Scotia Sea, −59.6988, −28.352016, 1451 m. Coll. British Antarctic Survey. 1 wet spec. R=3.3 r=1.5.