Bathyceramaster inornata, 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 : 31-32

Bathyceramaster inornata n. sp.

FIGURE 10A–F

Etymology: The species epithet is derived from the Latin word, “ inornatus ” for “unadorned” referencing the lack of marginal spines.

Diagnosis. Body stellate. R/r=4.18, arms elongate. A species distinguished by the coarse granules present on the abactinal plates as well as the spine-free granule covered marginal plate surface. Pedicellariae not observed on surface of holotype. Marginal plates with a strong abactinal facing, approximately 2.0/11 (out of disk diameter r= 11 mm)=18–27% of disk diameter. Marginal plate surface of both superomarginal and inferomarginals with approximately 40–200 (mostly 150–170) polygonal, widely spaced granules which are consistent with those on the abactinal plate surface. Furrow spines 9–12, blunt, thin and finger like in weakly curved to straight series. Subambulacrals four to six with central one to three enlarged.

Comments. Very similar to the northern form of Bathyceramaster elegans observed on the west coast of North America. Major distinctions of Bathyceramaster inornata n. sp. include, the absence of pedicellariae from the proximal adambulacral plates as well as the absence of nubbin-like spine from the inferomarginal plates. No actinal pedicellariae observed, actinal granules are short spinelets versus those in the North Pacific B. elegans which has pointed granules (i.e. triangular, quadrate in cross-section). Oral spinelets not identical in height, but decreasing in height from distal to proximal. Abactinal plates narrower along arm with only three rows versus six in the North Pacific specimens ( Fig. 10A, E ).

Bathyceramaster n. sp. shares several characters with Bathyceramaster elegans including a similar number of furrow spines (9–12 vs. 9–15 in B. elegans ) and identical types of granules present on the abactinal tabulae.

Occurrence: Johnston Atoll, 1165 m.

Description. Body strongly stellate (R/r=4.18). Arms elongate, triangular in shape, interradial arcs curved ( Figs. 10A, C, E ).

Abactinal surface composed of low columnar tabulae ( Fig. 10 A-inset), which appear lower distally along arm. Stellate radiating bases absent. Larger primary tabular plates present interradially ( Fig. 10B ). Central apical plate approximately two to three times as large as adjacent abactinal plates. Abactinal plates decrease to a single series approximately halfway along arm, forming single series to armtip. Plate surface covered with three to 40 widely spaced, angular quadrate to polygonal granules ( Fig. 10A inset). Disk and radial regions with five to 26 widely spaced peripheral angular granules. Plates also with two to 20 central, widely spaced round to polygonal granules. Abactinal plates along distal arm region and disk interradii more homogeneous, showing less differentiation between peripheral and central granules ( Fig. 10B ). Central granules with highly variable arrangement ranging from single line of 6–10 in a triangular shape. Papulae present on disk and approximately half of arm distance. Abactinal plates with discrete but well-developed fasciolar grooves along radial regions overlapping with papular areas, becoming shallower interradially and distally along arm. Madreporite with well-developed sulci, eyedrop-shaped, flanked by four adjacent plates. Pedicellariae not observed. Abactinal plates in discrete transverse series present interradially ( Fig. 10B ).

Marginal plates with a strong abactinal facing, approximately 2.0/11 (out of disk diameter r= 11 mm)=18–27% of disk diameter ( Fig. 10A ). Approximately 52–58 superomarginals/inferomarginals from armtip to armtip (26–29 per arm) but slightly offset along arms, resulting in zig-zag contact. Superomarginals wide, forming distinct dorsolateral-border ( Fig. 10A ). Inferomarginals are more strongly convex, especially interradially, with more elongate plates distally. Superomarginals and inferomarginals trapezoidal in outline proximally becoming more quadrate distally ( Fig. 10D ). Marginal plate surface of both superomarginal and inferomarginals with approximately 40–200 (mostly 150–170) polygonal, widely spaced granules which are consistent with those on the abactinal plate surface ( Fig. 10D ). Although peripheral granules can be distinguished from those on the central plate surface they are poorly differentiated and are nearly indistinguishable. No pedicellariae observed on marginal plates. Terminal plate triangular, covered by granules with three short spines.

Actinal intermediate areas with three full series of plates with two to five plates in irregular series adjacent to inferomarginal plates ( Fig. 10C, F ). Actinal plates present on disk and only the basal arms. Plates are quadrate to variably polygonal in shape with 11–45 spiny, widely-spaced, angular granules present on each plate surface ( Fig. 10F ). Peripheral granules, 7–12 on each plate, variably 3–4 per side. Granules largest on each plate corner pointing distally but smaller on plate surfaces proximally but overall granules becoming more homogeneous on plates distally adjacent to inferomarginals. Discrete shallow fasciolar grooves present between actinal plates.

Furrow spines 9–12, blunt, thin and finger like in weakly curved to straight series ( Fig. 10F ). Furrow spines set apart by a space from two rows of subambulacral spines ( Fig. 10F ). Row of subambulacrals behind furrow spines, four to six with central one to three enlarged, ranging from equivalent in length to furrow spines to approximately 70% of furrow spine height. Third row of short, 25% of furrow spines, widely spaced subambulacral spines present, nearly identical to those granules on actinal intermediate surface becoming continuous with granules on the actinal intermediate surface. Oral furrow spines ten with four present on the oral plate apex bearing two most elongate, blunt spines projecting into the mouth. Oral plate surface with ten paired spinelets present along midline along contact with other oral plate, A further ten irregularly arranged widely spaced spinelets present on oral plate surface. Oral plate surface is otherwise bare.

Color in life white ( Fig. 11E ).

Material Examined. Holotype. USNM 1457371, Johnston Atoll, North Pacific Ocean, 15º41’N 170º22’W, 1165 m, Coll. C. Mah & C. Kelley aboard NOAA Ship Okeanos Explorer -using ROV Deep Discoverer. 22 July 2017, EX 1706. 1 wet spec. R =4.6 r=1.1 R /r=4.18

Images Examined

Northern Wake Island, Wake Island region, 19.44510356, 165.7980054, 2110 m EX1606 _IMG_20160806 T030429 Z_ ROVHD _ ASR.jpg

Northern Wake Island, Wake Island region, 19.44364478, 165.7999808, 2047 m EX1606 _IMG_20160806 T044938 Z_ ROVHD _ ASR.jpg

Figures

FIGURE 10. Bathyceramaster inornata n. sp. USNM 1457371 (Holotype) A. Abactinal view. Scale bar=5.0 mm. Inset: Granules on abactinal plates. Diameter of individual plates=1.0 mm. Specimen partially damaged during collection, but also dissected for identification. B. Close-up showing disk plates and patterns. Scale bar=2.0 mm. C. Actinal surface. Scale bar=5.0 mm. D. Abactinal-lateral view showing superomarginal and inferomarginal plates. Scale bar=2.0 mm. E. In situ observation of holotype specimen, Johnston Atoll, 1165 m. F. Adambulacral armament, including furrow spines and subambulacral spines. Scale bar=1.0 mm.

FIGURE 11. Bathyceramaster smithi (Fisher, 1913) USNM 1424227. A. Abactinal view. Scale bar=3.0 mm. B. Close-up of abactinal plates. Scale bar=1.0 mm. C. Actinal view. Scale bar=3.0 mm. D. Lateral view showing inferomarginals. Scale bar=2.0 mm. E. Close-up of oral and adambulacral spination. Scale bar=1.0 mm.