Atheraster luma, Mah, 2023

Mah, Christopher L., 2023, New Goniasteridae and in situ observations significant to deep-sea coral predation, Memoirs of Museum Victoria 83, pp. 1-35 : 6

Atheraster luma n. sp.

urn:lsid:zoobank.org:act:904FBE9F-371B-48B5-9165-

1358E6B574F4

Figure 2a–g

Etymology. A Latin word for thorn, alluding to the many conical spines present on the marginal plates.

Diagnosis. Body shape weakly stellate to stellate (R/r=2.0– 3.3), arms triangular, relatively short. Abactinal plates bare, flat. No spines. All marginal plates with a single, conical spine in series; plate surface otherwise bare. Pedicellariae paddle-like in shape. Actinal plates with pedicellariae, angular granules. Furrow spines, 4 to 9. A single large, thick subambulacral spine present behind furrow spines with large, distinct, bivalve paddle-shaped pedicellariae proximal to the spine on each adambulacral plate.

Comments. Atheraster luma n. sp. shares a full series of single, conical spines present on all marginal plates with A. symphonia but differs from the other two Atheraster species, which have multiple spines present in each interradius. The functional significance of different, larger spination in each interradius is unclear, perhaps representing phenotypic variation relative to predation by differing prey species.

Occurrence . Tasmanian seamounts. 900–1450 m.

Description. Body strongly stellate (R/r=3.06–3.2), arms elongate to triangular, interradial arcs weakly curved to straight. Disk surface formerly inflated with deflated texture. Arms upturned.

Abactinal surface flat, individual plates polygonal and triagonal to round, directly abutted. Plates extending to arm tips, size variable, relatively homogeneous on disk acutely heterogeneous on arms with smaller plates (~25% of the size of larger plates) adjacent to larger ones. Disk plates flatter on disk, becoming more convex along arms. Individual plates each surrounded by 10–40, mostly 15–30, quadrate to polygonal granules forming a single series around the periphery of every plate. Most plates bare with no granules or other accessories but central disk region plates covered with 5–10 small granules, especially adjacent to the madreporite, with one plate showing especially large granules. Madreporite convex, sulci well developed. Plates on arm in approximately three irregular series, decreasing to one distally. Carinal disk plates appear widest and largest along arm. Papulae present along radial regions, 4–6 per plate, each papula at disk edge. Pedicellariae paddle-shaped, present on a minority of plates, especially on radial and interradial regions.

Superomarginal plates 32–56 per interradius (arm tip to arm tip), inferomarginals 32–58 (larger plate count in larger individuals, R=7.3). Individual plates wide (W>L) throughout but with more lateral facing interradially. Marginal plates associated 1:1. Each superomarginal plate with a single prominent tubercle or short conical spine, especially interradially, becoming flattened out distally near arm terminus. Superomarginal plate surface bare save for small 2.0 mm pedicellariae present on lower lateral facing adjacent to peripheral granules and contact with inferomarginal plate. Spines/tubercles on marginal series arranged in distinct linear series in parallel to one another. Inferomarginal plates with single spines/tubercle absent interradially but present in three of the five arms from arm base to tip, one paratype (F240317) with one or two spines present on interradial inferomarginals. Distal-most superomarginals and inferomarginals strongly convex with swollen distinct region, but lacking spines. Interradial inferomarginal plates with 5–30 angular, irregularly shaped granules, especially on the actinal plate facing. Lateral inferomarginal plate facing is mostly bare except for one small 2.0 mm paddle-shaped pedicellaria present on the inferomarginal adjacent to the contact with the peripheral granules and the superomarginal plate. Each marginal plate with approximately 50–80 quadrate-shaped granules forming periphery around the edge. Smaller individuals (R=3.9) with fewer pedicellariae present on inferomarginal plates. Terminal plates large, triangular, surface smooth with two short spines.

Actinal surface composed of three or four rows of plates in chevron-like pattern. Each plate covered by 2–12 irregularshaped angular to polygonal granules, densely arranged. Centrally present on most of these plates is a large bivalve paddle-shaped pedicellariae (1.0 mm across for each valve), especially proximally adjacent to oral plates. Granules adjacent to pedicellariae are approximately twice as large as other granules. Actinal plates with large, blunt spines distally.

Furrow spines 4–9, with some individuals showing 5–8 and others (e.g. at R=3.6) with nine, quadrate in cross-section but variably thin or thick. Furrow spines straight to weakly palmate in arrangement. A single large, thick subambulacral spine present behind furrow spines with large, distinct, bivalve paddle-shaped pedicellariae proximal to the spine on each adambulacral plate. Subambulacral spine becomes larger and more pronounced distally, especially as other ambulacral spination accessories become smaller.

Oral furrow spines 9–12 per plate, each with a single blunt spine directed into mouth. Oral plate surface with two series of nine angular granules paired across the contact between oral plates. Remainder of oral plate with irregularly arranged granules present on surface.

Material examined. Holotype. NMV F122778 , 82.6 km SSE of South East Cape, “J1” seamount. 44.24° S, 147.36° E, 1200–1450 m, 27 Jan 1997, coll. Museums Victoria and T. N. Stranks, CSIRO, R / V Southern Surveyor “Seamount” cruise ( SSO)197). 1 wet spec, R =7.3, r=2.2.