Bathyceramaster teres, 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 : 36-39

Bathyceramaster teres n. sp.

FIGURE 12A–F

Etymology. The species epithet teres is Latin for “rounded or smooth” alluding to the weakly convex, bald plates on the distalmost marginal plates.

Diagnosis. Body thick, weakly stellate (R/r=1.77), interradial arcs weakly curved. Lateral edge is thick and rounded. Abactinal plates tabulate, fasciolar grooves well-developed. Abactinals and marginal plates with coarse granules, abactinal plates each with four to fifty granules, most with 8 to 35. Ten distalmost superomarginal plates with quadrate, bald region, otherwise marginals covered by coarse granules. Pedicellariae tong-like with two or three valves, when present on actinal surface. Furrow spines, 4 to 7 with 2 to 4 subambulacrals (mostly 3). Actinal plates with dense covering of coarse granules similar to those on the abactinals.

When alive, specimen was orange with lavender to purple colored marginal plates.

Comments. A species which is identified as a species in Bathyceramaster based on the dense abactinal granulation on abactinal, marginal and actinal plates, tabulate abactinal plates and well-developed fasciolar grooves as described by Mah (2016b). Bathyceramaster teres n. sp. is distinguished from Bathyceramaster inornata n. sp. on the basis of its less stellate body shape with shorter arms (R/r=1.77–2.66 versus 4.18), fewer furrow spines (5–7 versus 9–12 in B. inornata ) and the presence of discrete bald patches on the distalmost marginal plate surfaces ( B. inornata with fully covered marginals). This bald region on the marginal plate surfaces also distinguishes Bathyceramaster teres from the North Pacific Bathyceramaster careyi Mah 2016b . The body shape of B. teres n. sp. is less stellate with shorter arms (R/r=1.77–2.66) than that of the North Pacific B. careyi (R/r=1.89–3.83). The paratype (USNM 1467554) is further distinguished from B. careyi based on the possession of tong-shaped bivalve or trivalve pedicellariae on the actinal surface.

Bathyceramaster teres n. sp. has several characters, suggesting affinities, which are similar to the North Pacific Bathyceramaster careyi . The abactinal plates and granules on the plates surfaces are similar and both furrow spination and subambulacral spination also resemble those in B. careyi .

In Situ Observations : When collected, USNM 1453747 was hunched over a glass sponge in the genus Waltheria ( Fig. 12D ). Following collection, the specimen had sponge spicules and tissue in the oral region suggesting it had been feeding on the sponge. This would be consistent with prior feeding observations of this species on deep-sea sponges ( Mah 2016a).

The Sibelius specimen (USNM 1467554) was observed on a basalt bottom with a light epizoic cover. One arm on that specimen was extended upwards away from the bottom.

Occurrence: Howland Island and Sibelius Seamount, North Pacific Ocean. 2175–2439 m.

Description: Body thick, weakly stellate (R/r=1.77–2.66) in outline, interradial arcs straight to weakly curved. Arms triangular. Armtips blunt ( Fig. 10A ).

Abactinal plates tabulate, fasciolar grooves well-developed. Abactinal plates round to polygonal ( Fig. 10 Ainset). Plates extend along arm, with single carinal plate series adjacent to armtip. Each abactinal plate with coarse granules, four to fifty, mostly with 8 to 35. Fewest granules present distalmost on abactinals, adjacent to superomarginal contact with highest number of granules on disk. Central disk granules vary in size relative to peripheral granules with some granules identical in size to peripherals, 25–45 centrally, 30–40 peripherally ( Fig. 12A ). Most other plates, especially along radial regions with central granules at least 1.5 to three times as large as the peripherals, ranging from a large single to two central granules surrounded by 7–10 to 10–15 central large granules. Granules most widely spaced radially, becoming more densely arranged interradially, especially adjacent to superomarginal contact. Papulae six per plate, resulting from openings around each plate. Madreporite weakly convex with welldeveloped sulci, flanked by six abactinal plates. Pedicellariae variably absent (USNM 1453747) to weakly present (USNM 1467554) with the latter specimen displaying only two to four tong-like pedicellariae per interradius.

Superomarginals 22–24 per interradius (armtip to armtip) both superomarginals and inferomarginals very wide (W>L). Superomarginals primarily situated on the abactinal side with inferomarginals forming lateral ledge out away from superomarginals. Contact between superomarginals and inferomarginals offset forming zig-zag contact between them. Marginal plate surfaces flat to weakly convex. Marginal plates covered by coarse granules, 40–80, mostly 30–70 covering plate surface, approximately five to seven along a 1.0 mm line ( Fig. 12B ). Peripheral granules, 70 in total with 10 on each long side, 25 on each wide side interradially. In situ observations suggest that granules cover marginal plates along the entire distance. Granules largest on plate surface where superomarginal and inferomarginal are in contact with one another becoming more in line with size on actinal plate surface. Distalmost plates, numbering 2 to 4 with distinct, weakly convex bare region on the plate surface ( Fig. 12D ). Bare region smooth, with no pitting or convexities. Peripheral region of these plates with one to four series of granules present, numbering 20, 40 total. Terminal plate circular, convex relatively large, about three times the size of the carinal plates adjacent to it. No pedicellariae observed on marginal plates.

Actinal surface composed of 5–7 plate series in chevron arrangement ( Fig. 12C, E ). Three or four series complete with one or two series adjacent to the inferomarginals incomplete in irregular series. Individual plates quadrate to polygonal in outline. Weakly developed fasciolar grooves present. Actinal plates with coarse granules three to 20 per plate, granules widely to densely spaced. Granules round to quadrate in shape. Pedicellariae, when present, are tong-like with two or three valves. When present, one pedicellariae present every three plates on the actinal plate series adjacent to the adambulacral plates ( Fig. 12 E ). Pedicellariae occurrence variable even on a single individual (USNM 1467554) with only two interradii displaying abundant pedicellariae, the other three largely lacking all but one or two pedicellariae. One specimen (USNM 1453747) displayed no pedicellariae on its actinal surface.

Furrow spines 5–7, short, blunt in weakly palmate convex formation ( Fig. 10F ), rounded in cross-section. Furrow spines set apart from other adambulacral spination by discrete rounded space. Adambulacral plates rounded in shape. Subambulacral spines, 2–4, twice as thick as each furrow spine ( Fig. 10F ). Pedicellariae, present in place of subambulacrals on proximalmost three adambulacral plates. Pedicellariae tong-like, similar in size to two to three times thickness of the subambulacral spines. Adambulacral plate surface covered by six blunt granules/spines on remainder of each plate decreasing in size becoming continuous with granules on actinal plate surface. Oral plates with nine to ten furrow spines. Oral plate surface with 4–6 thick spines, each approximately two to three times as thick as oral plate furrow spines, plate otherwise bare. Oral plate and adambulacral plate details damaged during collection and so, some details are obscured.

In situ observations show this species as white or orange ( Fig. 10G ). The Howland Island specimen (USNM 1453747) displayed lavender coloration along its superomarginal plate series. The other specimen (USNM 1467554) showed the more uniformly orange to yellow color with darker purple to lavender marginal plates. This suggests some variation in color within the species, possibly associated with the differently sizes of each specimen.

Material Examined: Holotype. USNM 1467554 Sibelius Seamount , North Pacific, Papahuanaumokuakea Marine National Monument, 27.25/-160.63 (27º15’N 160º38’W) 2439 m, Coll. M. Putts, NOAA Ship Okeanos Explorer EX1708 , dive 04 (20170911/004747). 1 wet spec. R =3.2 r=1.2 EX1708 _IMG_20170911 T003849 Z_ ROVHD.jpg

Paratype. USNM 1453747 Howland Island, Central Pacific Basin. 0º48’N, 176º 40’W, 2175 m, coll . NOAA Ship Okeanos Explorer using the D2 ROV, 18 March 2017 EX1703 . 1 wet spec. R =2.3 r=1.3. EX1703 _IMG_ 20170318 T225549 Z_ ROVHD.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 12. Bathyceramaster teres n. sp., USNM 1453747 Holotype. A. Abactinal view. Scale bar=5.0 mm. Inset showing granulation on abactinal plates. Diameter of individual plate=0.75 to 1.0 mm. B. Abactinal-lateral view showing granulation on superomarginal plates. Scale bar=3.0 mm. C. Actinal view. Scale bar= 5.0 mm. D. Close-up showing bald spots on distal superomarginal plates. Scale bar=2.0 mm. E. Actinal view closeup showing pedicellariae on actinal and adambulacral plates. Scale bar=1.0 mm. F. Adambulacral spination, showing furrow and subambulacral spines. Scale bar=1.0 mm. G. In situ observation of the paratype of B. teres feeding on the glass sponge, Waltheria. R of specimen is 2.3 cm.