Heligmaster kanaloa, 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 : 21-23

Heligmaster kanaloa n. gen. n. sp.

FIGURES 6A–F , 8A–B

Etymology: The species name honors Kanaloa, the Hawaiian god of the Ocean, whose association with squids and octopi is especially relevant to the cephalopod like arms on this species. Noun held in apposition.

Diagnosis. Stellate (R/r=4.3 at R=7.0) body form with strongly curved arms.

Disk with delicate, glassine, imbricate plates embedded in abactinal surface, each with one or two short spinelets. Marginal plates in single series with pointed, glassine spines, 3–6 bearing thornlets, spines on a short, rounded base. Subambulacral plates correspond 3 for every 1 marginal plate with a smooth, accessory-free dermis-covered region between them on lateral arm surface. Subambulacral plates with spines, 1–3 set on a round base. Spines similar to those on marginal plates, pointed and elongate, glassine with thornlets. Furrow spines, 3–5, webbed, dermis covered, arranged in straight to weakly curved fans, forming a near continuous series along tube foot groove.

Color in life: different individuals are white or orange. Orange individuals had dark orange tube feet. White individuals had dark tan tube feet.

Comments. Several images of Heligmaster n. gen. were made without a specimen collection. Identification of these images was based on the fewer spine counts of the superomarginal paxillae as H. kanaloa n. sp.

Observations of differing color variations suggest two distinct color variations, one orange and one white. It was unclear, if color had any significance relative to size or if it was regional variation.

Occurrence: Hawaiian Islands, Johnston Atoll, McCall Seamount, Midway and American Samoa 2091–3916 m

Description. Body strongly stellate (R/r=~4.3) with elongate, with tapering, curved arms, extending below the disk ( Fig. 6B ).

Abactinal surface composed of thin, delicate translucent dermis, plates weakly developed minute. Underlying features, such as ambulacrals and sediment infused stomach visible through the abactinal surface. Surface with short glassine spinelets, mostly with single pointed tip but a minority of spines with bifid tips and covered by weakly developed dermis ( Fig. 6A ). Spinelets evenly distributed over surface, approximately 2 to 3 counted along a 1.0 mm line on disk and arms becoming more widely distributed and more weakly developed distally along arms but absent along a narrow strip interradially on disk. Papulae single, present most abundantly on proximal arm region. Absent from central disk and distal arm. Anus located centrally on disk, formed by relatively large, opening, approximately 1.5 mm in length. Madreporite large, raised above surface of body, approximately 3 mm in width with well-developed sulci. No pedicellariae observed.

Single row of widely spaced marginal plates forming single series along upper edge of lateral side. Lateral surface and plates covered by thick dermis. Lower edge composed of adambulacral plates along lower edge of lateral surface. Approximately one marginal plate for every three adambulacral plates. Marginal plates, 44 per interradius (armtip to armtip), each with 3 to 6 sharp spines, sitting on a mound-like, pedunculate base, 1 spine demonstrably longer than the others on each plate. Spines glassine with surface bearing tiny thornlets. Spacing between marginal plates widest proximally, shortest adjacent to armtip. Lateral region between marginal plate boundary to adambulacral series, covered by distinct dermis, smooth mostly devoid of spines or other features save for one or two small spinelets proximally. Terminal plate toe-shaped, tipped with four pointed spines. Note that subambulacrals positioned adjacent to marginals on lateral surface in approximately “inferomarginal plate” position.

Subambulacral spines correspond roughly three plates to every one marginal plate. Large subambulacral spines emerge from adambulacral plate number 92 per interradius (armtip to armtip) corresponding roughly every 3 to every 1 marginal plate. Each with a round pedunculate base similar to marginal plates, with 1 to 3 pointed spines per plate. Furrow spines 3 to 5, forming straight to weakly curved fans, each spine short, webbed, sheathed in tissue forming a nearly continuous series adjacent to the tube foot furrow. Furrow spine arrays sit a distinct distance away from subambulacral plates. Intervening distance covered by thick dermis. Proximal-most furrow spine short, distinct, with spatulate, tissue covered tip and at an oblique angle to the other furrow spines. Adambulacral plates broadly mound-shaped, convex surface facing into furrow, each plate distinctly separated from one another by tissue. Surface covered by thick dermis. Oral plate with webbed furrow spines, 7 per plate, totaling 14 per interradius. Oral plate surface with 3 to 4 pointed spines separate from furrow spines. Fissure between oral plates well developed. No pedicellariae observed.

Tube feet muscular with ring-shaped tip. Podial pores remain biserial throughout, but drawing together very closely on distalmost armtip (approximately 10 plates from terminal) giving the appearance of switching from biserial to monoserial near terminus. Pyloric stomach well developed, partially extended ( Fig. 6E ).

Ambulacral ossicles viewed laterally with head projecting proximally broadly angular in outline, neck with flat surface, base quadrate n shape ( Fig. 6C ). Color of living specimens was orange and white ( Fig. 8A, B ). Material Examined. Holotype. USNM 1457376 , Johnston Atoll, North Pacific Ocean. 15.17, -171.25, 2568 m, Coll. NOAA ship Okeanos Explorer (NOAA) , Chris Mah and C. Kelley. EX 1706 . 1 wet spec. R =~7.0, r=1.6.

Images Examined orange forms. McCall Seamount , Hawaiian Islands 18.979054, -157.1102457, 2655 m. EX1504 L3_IMG_20150831 T231915 Z_ ROVHD _ ASR _ AUD.jpg

Wetmore Seamount , Johnston Atoll region, 15.16622471, -171.254609, 2569 m EX1706 _IMG_20170723 T202554 Z_ ROVHD.jpg

white forms. South Midway Atoll 25.35988374, -178.4292349, 3916 m to 25.35988775, -178.4292251, 3916.6 m (for both images below)

EX1603_IMG_20160311T233015Z_ROVHD_ASR_COR_BAR_CRI.jpg EX1603_IMG_20160311T233044Z_ROVHD_ASR_COR_BAR_CRI.jpg

Moki Seamount , American Samoa region -11.16848593, -169.8921686, 2091 m EX1702 _IMG_20170222 T222707 Z_ ROVHD.jpg

Figures

FIGURE 6. Heligmaster kanaloa n. gen., n. sp. USNM 1457376 A. Abactinal disk surface. Scale bar=2.0 mm. B. Lateral view, whole body. Scale bar=5.0 mm. C. Cutaway of ambulacral and adambulacral ossicles. Disk is on right side. H=ambulacral head, N=ambulacral neck, B=ambulacral base, Ad= adambulacral plate. Scale bar=1.0 mm. D. Lateral view of abactinal surface, superomarginal, inferomarginal paxillae. Scale bar=2.0 mm. E. Actinal surface showing furrow spines. Scale bar= 5.0 mm. F. Close-up of furrow spination, tube foot furrow. Scale bar=1.0 mm.

FIGURE 8. In situ images. Heligmaster kanaloae n. gen. n. sp. A. Orange color morph. McCall Seamount, Hawaiian Islands. 2655 m. Imaged on vertical rock face. B. White color morph. South Midway Atoll region, 3917 m. Atheraster arandae C. Short armed morph. Salmon Bank, Hawaiian Islands. 2007 m. D. Long-armed morph. Salmon Bank, Hawaiian Islands, 1949 m. E. Rose Atoll, American Samoa, 2439 m. Atheraster sp. F. Bank Nine, Hawaiian Islands, 1635 m. G. Hawaiian Islands,