Heligmaster pele, Mah, 2022

Mah, Christopher L., 2022, New Genera, Species and Occurrences of Deep-Sea Asteroidea (Valvatacea, Forcipulatacea, Echinodermata) collected from the North Pacific Ocean by the CAPSTONE Expedition, Zootaxa 5164 (1), pp. 1-75 : 23-25

Heligmaster pele n. sp.

FIGURE 7 A-G

Etymology. This species is named for Pele, the Hawaiian god of volcanos alluding to the basalt substrate on which this species was collected. Noun held in apposition.

Diagnosis. Body strongly stellate (R/r=7.7–8.6), arms elongate and strongly recurved. Abactinal spines, glassine delicate clusters 1–4 per plate, sitting on similarly delicate, glassine plates. Marginal plates with short, round base, displaying 15–20 spines with 1 or more especially elongate. Marginals show 1 to 3 correspondence with subambulacrals. Lateral area between marginal and subambulacral mostly smooth but with small mound-like plates showing 2 to 6 sharp, pointed spines on disk and proximally on arms. Subambulacrals with 6 to 8 spines. Actinal intermediate area present, covered with spine clusters, each with 3 to 5 spines. Furrow spines unwebbed, acicular, 1 to 5, mostly 4 or 5 proximally.

Comments. Heligmaster pele n. sp. differs from Heligmaster kanaloa n. sp. in the possession of larger numbers of marginal and subambulacral plate spines, unwebbed furrow spines and a much greater arm to disk ratio (R/r). These characters were consistently observed in both individuals, a smaller (R=2.6) specimen and a much larger (R=14.7) one. The holotype of Heligmaster kanaloa n. sp. is much smaller (R= approximately 7.0) than the holotype of Heligmaster pele n. sp. but displays fewer marginal and subambulacral plate spines, webbed furrow spines and has much less of an arm to disk ratio. Papulae were absent in the smaller individual but abundant in the larger holotype suggesting a size-related expression of this character. The larger holotype of Heligmaster kanaloa , also displays papulae which appears consistent with the size-related expression of this character.

In situ observations of this species by the R/V Nautilus were made of both the smaller white individual and the larger orange individual ( Fig. 7F ). However, as with Heligmaster kanaloa n. sp. trends in coloration are not evident from available observations.

Occurrence: NW of the Hawaiian Islands, 2407–2776 m.

Description. Body strongly stellate (R/r=7.7–8.6) with elongate, tapering arms with recurved distalmost tips. Disk thick, interradial arcs acute, body strongly concave.

Abactinal surface covered by a thin membrane through which interior details such as the distalmost ambulacrals and stomach/disk structures are visible ( Fig. 7A ). Surface covered with delicate polygonal, flattened, imbricate plates, nearly translucent on disk at R=2.6, each covered by short spines, 1 to 4 per plate, ensacculate, widely spaced on each plate ( Fig. 7B ). Plates with multiple spines present proximally but becoming predominantly single spines distally along arm, these all widely spaced from one another. Papulae single with greatest abundance proximally on each arm, arranged into roughly four series along arm distance, pinching out distally. Papulae absent in smaller specimen (R=2.6). In smaller sized individual (R=2.6), abactinal spines are much finer and much more needle-like, numbering 1 to 4 ( Fig. 7E ). On large sized specimen (R=7.7) spines cover the complete disk surface, including the interradial regions, but the smaller individual displays naked, interradii on the disk. Madreporite large ( Fig. 7B ), approximately 4 mm in diameter at R=7.7, 0.75 mm at R=2.6, circular in shape, raised well off the surface of the abactinal surface. Anus covered by pointed, acicular spinelets, approximately 9 around opening. No pedicellariae observed.

Marginal plates widely spaced ( Fig. 7C ) with 15–20 (mostly 15–18) jagged spinelets with one central sharp spine dominating. Spines pointed, glassine with tiny thornlets. Marginals, 52 per interradius (armtip to armtip) twice the size of the adjacent subambulacral spines. At R=2.2, marginal plates, 26 per interradius (armtip to armtip) with very fine spines, 12–20 delicate, almost hair-like. Spacing between marginal plates widest proximally, shortest adjacent to armtip.

Subambulacral plates mound-like bearing sharp-spines, 6 to 8, numbering 150 to 162 per interradius (armtip to armtip)at R=7.7. Subambulacrals number approximately three times as many marginals with 1 marginal spaced for every 3 adambulacral and distinctly separated by dermal covered surface. Furrow spines 1 to 6, mostly 5 or 6 with distalmost arm bearing single acicular spine. Each spine covered with weakly developed dermis but otherwise unwebbed ( Fig. 7F ). Smaller individual (R=2.2) with 1 to 5 acicular, completely free spines, delicate almost hairlike in texture. Oral plates with 12–15 furrow spines forming serial perimeter around oral plates ( Fig. 7D ). Each oral plate with 3 enlarged spines projecting into mouth, (6 per interradius). Oral plate surface with 3 to 4 spines, total 6 to 8 per interradius.

Actinal surface covered by thick dermis forming discrete transverse segments forming contiguous associations between adambulacral and marginal plates. These segments are contiguous with the lateral areas along the arms between the marginal plates and the adambulacral plates. These lateral areas are smooth and bare along the arm, but adjacent to the disk, covered by 1 to 3 mound shaped plates (obscured by dermis) each bearing 2 to 6 sharp spines ( Fig. 7D ). Fewer spines distally, plates on actinal intermediate “segment” with greatest number of plates (three) with each bearing 3 to 6 spines.

Ambulacral head viewed laterally, head rounded directed proximally, neck flat, base quadrate to spoon shaped.

Pyloric stomach well-developed, extended on holotype, surface covered with black coloring ( Fig. 7D ).

Tube feet, muscular with a well-developed ring shaped tip. Podial pores biserial but becoming more crowded distally giving the appearance of a single row of tube feet adjacent to armtip.

Color in life orange and white.

Material Examined. Holotype. MCZ 151023 , Hawaiian Islands . 25.4033117059, -163.9256143, 2407 m, Coll. ROV grab, Hercules / Argus aboard E/ V Nautilus , 29 Sept. 2018. 1 wet spec. R =~14.7, r=1.9.

Paratype. MCZ 151015 , Hawaiian Islands . 25.319824225, -163.741351845, 2776 m, Coll. ROV slurp gun, Hercules/Argus aboard E / V Nautilus , 30 Sept. 2018, 1 wet spec . R =2.6, r=0.3.

GONIASTERIDAE

Comments. The Goniasteridae is the largest and most diverse family of Asteroidea, including over 270 species in over 70 genera ( Mah & Blake 2012); representatives have been reported from all oceans and all depths, including the abyss (> 3000 m). Although the most heavily sampled Goniasteridae during the CAPSTONE expedition were the corallivorous Hippasterinae , a broad morphological diversity of taxa were sampled. Okeanosaster hohonui n. gen. n. sp. is a species that displays unusual morphological characters not previously seen from lower bathyal and abyssal settings. CAPSTONE collections also suggest that diversity for some groups, such as the subfamily Hippasterinae , remains poorly understood. A report on other in situ video observations and occurrence of goniasterids from the CAPSTONE campaign is currently in preparation.

Figures

FIGURE 7. Heligmaster pele n. gen., n. sp. Holotype MCZ 151023, Scale bar=5.0 mm unless otherwise noted. A. Abactinal body view. B. Close up disk surface showing madreporite, spines and papulae. C. Close up on marginal paxillae, furrow spines. D. Actinal surface showing mouth and tube foot grooves. E. MCZ 151015 paratype, (R=2.2) Smaller specimen showing disk characters, especially spination. Scale bar=0.5 mm. F. Close-up on holotype showing unwebbed furrow spines. Scale bar=2.0 mm. G. In situ observation. no scale.