Aquilonastra korora, O’Loughlin & Bribiesca-Contreras, 2017

O’Loughlin, P. Mark & Bribiesca-Contreras, Guadalupe, 2017, New asterinid seastars from the western Pacific Ocean (Echinodermata: Asteroidea), Memoirs of Museum Victoria (Mem. Mus. Vic.) 76, pp. 121-132 : 122-125

Aquilonastra korora sp. nov.

Zoobank LSID. http://zoobank.org/ urn:lsid:zoobank.org:act:

765787CA-CF22-4FF5-8637-497D9E9FA85D

Figures 4 , 5 , 6a–d .

Material examined. Holotype. Palau, Koror, Mutremdiu reef,rock, 30 m, coll. J. Starmer, 19 Aug 1995, code BEL–276, UF 2437 (fixed in formalin, dry; many spinelets and pedicellariae lost with handling over time).

Description. Asterinid seastar, five sub-equal rays nearly digitiform, rays wide basally, narrowly rounded to pointed distally, R = 25 mm, r = 10 mm, rays merge at bases, inter-radial junction of rays deeply in-curved, central rays elevated and rounded abactinally, weakly evident low sloping distal abactinal margin, no distinct apron; rays flat actinally, margin acute. Abactinal gonopores detected. Single madreporite. Not fissiparous. Fairly irregular series of superomarginal plates, subequal with adjacent abactinal and inferomarginal plates, inferomarginal plates project narrowly outwards. Narrow sloping margin up to about 5 plates across longitudinally, supported by some internal superactinal plates, distal marginal abactinal and actinal plates contiguous internally; superambulacral plates absent with tissue strengthening only of junction internally between ambulacral and actinal plates. Glassy convexities on cleared abactinal and actinal plates.

Abactinal: disc discrete, small, demarcated irregularly by 5 bean-shaped non-papulate radial plates and 5 slightly smaller inter-radial plates, disc plates papulate, distal abactinal plates on rays not papulate; single conspicuous madreporite, above junction of bases of two rays; pedicellariae present inter-radially, proximally, low, not conspicuous, each comprising two short thick blunt teeth, present on proximal edges of inter-radial plates over concave indentations for papulae; abactinal plates imbricate, indented proximally for predominantly 1 rarely 2 papulae; no regular carinal series of plates, rare doubly papulate carinal plates present; rare small secondary plates on disc and proximal upper rays; abactinal plates in about 3 longitudinal series down each side of each ray, plates with elevated rounded proximal edge, up to about 20 papular plates in uppermost series, about 10 in mid-series, about 4–7 in lowest series; distal inter-radial plates in longitudinal and irregularly distributed oblique series. Abactinal spinelets readily lost: abactinal spinelets finely sacciform with needle-like long taper, up to at about 16 spinelets across proximal raised edge of proximal plates, not in tufts, distal spinelets slender conical to subsacciform; up to about 2–3 small fine sacciform acicular spinelets on crowns of superomarginal plates.

Actinal: inter-radial plates in longitudinal series parallel to the ambulacral furrow, some oblique transverse series from the ambulacrum, distal inter-radials irregular in distribution. Actinal spines per plate: oral up to 9, long conical proximally, to short distally; suboral up to 6, 3 long conical proximally, 2–3 shorter on each side of plate distally; furrow 5–6 conical subsacciform, 2 long apically, 1–2 short laterally on each side of plate; subambulacral up to 8, 2 long subsacciform conical apically, 3 short conical on each side of plate; actinal predominantly 2, subsacciform conical; inferomarginal predominantly about 5 sacciform.

Distribution. Palau, rocky reef, 30 m.

Etymology. Named korora for Koror, the state in Palau where the type was collected.

Remarks. A diagnostic character of genus Aquilonastra is the presence of superambulacral plates. Aquilonastra korora sp. nov. is thus unique among Aquilonastra species in lacking such plates, but the species conforms well in most ways with the diagnosis of the genus and is assigned to this genus, with reservations, as the most appropriate existing genus. The presence of low pedicellariae with two short thick blunt teeth and predominantly 2 actinal inter-radial spines per plate are distinguishing characters. There are additional characters that distinguish Aquilonastra korora sp. nov. from other Aquilonastra species that have distinctive pedicellariae: Aquilonastra anomala ( Clark, 1921) and Aquilonastra corallicola ( Marsh, 1977) have up to 8 rays and are fissiparous with multiple madreporites; Aquilonastra batheri ( Goto, 1914) has tufts of splayed abactinal spinelets and up to 12 actinal inter-radial spines; Aquilonastra coronata ( Martens, 1866) has irregularly distributed high paxilliform abactinal plates with two different forms of spinelets; Aquilonastra iranica ( Mortensen, 1940) has up to 5 doubly papulate proximal carinal plates and the spinelets on proximal abactinal plates are in clusters; Aquilonastra rowleyi O’Loughlin and Rowe, 2006 has a disc that is delineated by a dense band of spinelets on wide radial plates, each plate with about 100 long thin pencil-like glassy spinelets; Aquilonastra shirleyae O’Loughlin, 2009 has spinelets in splayed clusters and up to 10 actinal inter-radial spines per plate; Aquilonastra watersi O’Loughlin and Rowe, 2006 has pedicellariae with differentiated valves but has doubly papulate proximal carinal plates and abactinal spinelets in clusters. All of these species have superambulacral plates. We note that Aquilonastra corallicola was described for Palau.

Figures

Figure 4. Montage photograph of the holotype of Aquilonastra korora sp. nov. (UF 2437). Abactinal view showing residual colouration, five sub-equal digitiform rays, absence of carinal series of plates, single large madreporite (lower arrow) and at least one conspicuous abactinal gonopore (upper arrow). The abactinal plates have become denuded of most spinelets over time.

Figure 5. Montage photograph of the holotype of Aquilonastra korora sp. nov. (UF 2437). Actinal view showing residual actinal colouration, five sub-equal rays, spination, longitudinal and oblique-transverse series of actinal plates with irregular distal inter-radials.

Figure 6. Montage photographs of the holotype of Aquilonastra korora sp. nov. (UF 2437): a, abactinal view of disc, showing disc plate arrangement, single large madreporite (top right), sacciform spinelets; b, abactinal details of distal interradius showing short blunt pedicellariae (highlighted) and residual slender conical, sub-sacciform and sacciform spinelets; c, actinal view showing oral, suboral, furrow and actinal interradial spines; d, transverse section of a ray with a superactinal plate highlighted.