Crossaster taitai, Mah, 2023

Mah, Christopher L., 2023, New Genera, Species, and observations on the biology of Antarctic Valvatida (Asteroidea), Zootaxa 5310 (1), pp. 1-88 : 48-51

Crossaster taitai n. sp.

FIGURE 15A–E

Crossaster multispinus McKnight 2006: 13 .

Etymology

The species name taitai is Maori for “brush” alluding to the highly spinose paxillae on the abactinal, marginal and actinal surface of this species. Noun held in apposition.

Diagnosis

Species with 11 arms (exceptionally 10) with relatively wide reticulate mesh. More closely arranged on the disk than on the arms ( Fig. 15A ). Abactinal paxillae displaying mostly 20–40 spinelets ( Fig. 15B ), approximately the length of the paxillar shaft. Paxillae most abundant and densely present on disk. Marginal plates 22–28. Superomarginals plates with 10–20 similar hyaline tipped spinelets. Inferomarginals forming distinct periphery, 3 to 5 times the size of the superomarginals with which they alternate. Inferomarginal plates with 15–40, mostly 20–30 hyaline-tipped spinelets ( Fig. 15D ). Actinal plates with 5–15 elongate spines. Furrow spines 6 to 9 with smaller individuals (R=1.7) bearing fewer (6 to 7) and larger individuals (R=7.2) bearing greater (8 to 9) spines, in palmate formation with weakly developed web around base of furrow spines ( Fig. 15E ). Subambulacral spines in single transverse series, 6–9, also with overall count increasing in larger individuals, ranging from 6 or 7 in R= 1.7 to 9 in R=7.2.

Comments

Crossaster multispinus sensu McKnight (2006) are described as having abactinal and actinal paxillae with 30–50, sharp, relatively short and delicate spinelets versus those on the type which number 15, long, sharp spinelets but shares an identical number of furrow (7 to 8, decreasing to 5 to 6 distally) and subambulacral spines (7 to 9). Review of his account plus examination of USNM specimens which correspond to the description in McKnight (2006) leads me to conclude that this species is different from Crossaster multispinus H.L. Clark, 1916 and is herein described as new. This species, including the description outlined for “ Crossaster multispinus ” in McKnight (2006) differs from that of O’Hara (1998: 182) on the basis of the paxillar spine number, greater than 30 with short spinelets in this species versus the 15 elongate spinelets as well as the more numerous furrow and subambulacral spines (only 5−6 furrow and 7 subambulacral spines) in the Macquarie specimen.

This species is characterized by the high number of spinelets on the abactinal, marginal and actinal paxillae presenting a very spinose appearance, drawing a parallel to Paralophaster antarcticus in displaying a hirsute appearance on its abactinal surface.

Description of this species based on the material listed in McKnight (2006) removes the occurrence of Crossaster multispinus in New Zealand but adds Crossaster taitai n. sp.

Occurrence

Off Tasmania and New Zealand, South Pacific from the Kermadec Islands to the Campbell Plateau. 39–1427 m.

Description

Arms 11, exceptionally 10. Body stellate, R/r=1.8–2.3 with gradually tapering arms, thick, triangular in outline. Interradial arcs acute ( Fig. 15A, B ).

Abactinal surface with reticulate skeleton, widely open spaces between narrow lobate plates. Reticulate mesh most open on arms, more closely spaced on central disk ( Fig. 15A ). Skin filled spaces between reticulate plates with papulae, 2 to 4. Abactinal plates with paxillae, each covered with a tuft of spinelets, 5 to 50, but mostly 20–40 ( Fig. 15B ) at R=3.3 to 7.2 with greatest numbers of spinelets on paxillae present on the disk with most central spineless elongate surrounded by shorter spineless around paxillae tip edge. Spinelets comparable or equivalent to length of paxillar shaft, with pointed tip and rough surface. Paxillar abundance and density appears highest on disk. Individual small spine covered plates also present on skin-filled regions within reticulate mesh. Madreporite triangular to irregularly shaped with well-developed sulci.

Marginal plates, 22–28 (R=3.3 to 7.2), most prominent are enlarged inferomarginals. Superomarginals smaller, similar to identical with abactinal paxillae, at oblique angles, alternating with the enlarged inferomarginals which are easily 3 to 5 times as large. Inferomarginals with curved head, covered by 15–40, mostly 20–30 hyaline-tipped spinelets similar to those on the abactinal surface at R= 7.2 cm. Superomarginals with 10–20 spinelets, similar to those on abactinal surface. Terminal plates, small double-trapezoid in shape.

Actinal intermediate region with 2 to 3 series of actinal paxillae present amidst skin filled surface, each plate with 5–15 slender spines ( Fig. 15C, D ). Some unspined plates present in actinal intermediate region, nearly obscured by skin. Note that inferomarginals and some abactinal paxillae to encroach onto the actinal surface on dried specimens ( Fig. 15D ).

Furrow spines, 6 to 9 with smaller individuals (R=1.7) bearing fewer (6 to 7) and larger individuals (R=7.2) bearing greater (8 to 9) spines, in palmate formation with weakly developed web around base of furrow spines ( Fig. 15E ). Subambulacral spines in single transverse series, 6–9, also with overall count increasing in larger individuals, ranging from 6 or 7 in R= 1.7 to 9 in R=7.2. Oral plates with 14–15 furrow spines with elongate, paired middle spines directed into the mouth. Furrow spines form close, curved array around periphery of oral plate. Oral plate surface ridged with raised central region and deep, enlarged central fossae. Each oral plate half with 7 to 8 spines on plate surface.

Material Examined

Holotype. USNM 1122444 , New Zealand, South Pacific Ocean. −40.267, 168.283, 913–915 m. Coll. R /V Eltanin, 2 Dec. 1966. 1 dry spec. R=3.3 r=1.7, 11 arms.

Paratypes. USNM 1123099 , Off Tasmania, Australia. −47.325, 147.858, 910–915 m. Coll. R/V Eltanin, 24 Feb. 1967. 1 dry spec. R=3.1 r= 1.3, 10 arms.

USNM 1122945 , NW of Chatham Islands, New Zealand, South Pacific Ocean. −44.0250, −178.15, 436–439 m. Coll. R/V Eltanin, 29 Nov. 1964. 1 dry spec. R=7.2 r=3.2, 11 arms.

USNM 1122442 , Cook Strait, New Zealand, South Pacific Ocean. −41.7, 175.425, 946–951m. Coll. R/V Eltanin, 31 Jan. 1965. 1 dry spec. R=1.7 r=0.9, 11 arms.

USNM 1676567 , Cook Strait, New Zealand, South Pacific Ocean. −41.7, 175.425, 946–951m. Coll. R/V Eltanin, 31 Jan. 1965. 1 dry spec. (fragments but overall diameter approximately 3.0 cm).

NIWA 2025 , Off east coast of New Zealand, South Pacific Ocean, −43.583333, −179.25, 413 m. Coll. NIWA, 24 Jan. 1968. 1 dry spec. R=6.2 r=2.7, 11 arms.

NIWA 45143 , Off east coast of New Zealand, South Pacific Ocean, −43.583333, −179.25, 413 m. Coll. NIWA, 24 Jan. 1968. 1 dry spec. R=6.0 r=2.8, 11 arms.

NIWA 45145 , Off east coast of New Zealand, South Pacific Ocean, −43.583333, −179.25, 413 m. Coll. NIWA, 24 Jan. 1968. 4 dry specs. R=8.2 r=3.5, R=6.9 r=2.6, R=6.1 r=2.6, R=2.9 r=1.2, all with 11 arms.

Figures

FIGURE 15. Crossaster taitai n. sp. Holotype USNM 1122444, A. Abactinal surface. B. Actinal surface. C. Closeup of abactinal paxillae showing spination. D. Actinal intermediate area showing inferomarginal plates. Actin=Actinal intermediate region, M=Inferomarginal plates. E. Adambulacral spines, showing furrow and subambulacral spination.