Ceramaster palmyra, Mah, 2024

Mah, Christopher L., 2024, New genera and species of deep-sea Goniasteridae (Asteroidea) from the North Pacific, Zootaxa 5543 (4), pp. 451-500 : 462-465

Ceramaster palmyra n. sp.

FIGURE 4A–E , 12B

Etymology

Species epithet is named for the type locality, Palmyra Atoll. Name is held in apposition.

Diagnosis

Body stellate (R/r=2.0), stout, arms triangular with curved interradial arcs. Abactinal plates with large peripheral granules and smaller central granules, the former approximately twice the size of the latter. Superomarginal plate tumid, significantly arched, abactinal surface completely bald, save for clustered granules on lateral side. Furrow spines slender, 4 –7, subambulacrals thick in 2 rows, 3 spines each.

Comments

Ceramaster palmyra n. sp. is based on the strongly tumid superomarginal plate dorsal surface, the absence of granulation from the superomarginal surfaces, slender furrow spines and large, trapezoidal granules on the abactinal plates. Peripheral abactinal granules are approximately twice the size of the central granules.

Although a full overview of Ceramaster spp. is beyond the scope herein, comparison of this species showed general morphological similarity with Ceramaster species that most closely cluster with C. patagonicus , which displays tabulate abactinal plates, a bald area on the superomarginal plates as well as trapezoidal peripheral granules which vary in size relative to the granules on the central region of the abactinal plate. This includes, but is not limited to the recently described Ceramaster vorax Mah 2022 as well as other Pacific species such as Ceramaster australis Clark & McKnight 2001 , Ceramaster arcticus ( Verrill 1909) , Ceramaster japonicus ( Sladen, 1889) , the Atlantic Ceramaster granularis (Retzius 1783) as well as C. patagonicus itself which is widely occurring at high latitudes. Other Ceramaster species, such as the deep-sea North Pacific Ceramaster pointsurae Mah 2016 show strong morphological affinities with the Atlantic Ceramaster grenadensis (Perrier, 1881) and based on character comparisons form a separate cluster from those which share characters with C. patagonicus .

This species is distinguished from C. vorax based primarily on the completely bald superomarginal plate surface, which in C. vorax is limited to a discrete region as well as the presence of pedicellariae, which were present in C. vorax , but not observed on Ceramaster palmyra n. sp. Subambulacral spines in C. palmyra n. sp. are similar in number and orientation to C. vorax but are smaller, more widely spaced and oriented in more regular series. Other shared characters between Ceramaster palmyra n. sp. and C. vorax , including similar abactinal plate granule shapes and identical furrow spine numbers. Among the known tropical Pacific C. patagonicus type species, these two show close morphological affinities.

Also similar, is the South African Ceramaster trispinosus H.L. Clark, 1923 , which differs in showing 3 furrow spines versus 4 to 7 in C. palmyra n. sp. and showing a complete cover of granules on the superomarginal plate surface where C. palmyra n. sp. displays a prominent bald patch.

All of the other “ C. patagonicus ” cluster species, such as C. patagonicus , C. arcticus , C. australis , and C. granularis , displayed substantially thicker, fewer and more elongate furrow and subambulacral spination than C. palmyra n. sp.

Given the widely occurring distribution and relatively slight character differences between species, further molecular tests of Ceramaster spp. are desirable.

Occurrence

Near Palmyra Atoll, 1373 m.

Description

Body stout, outline stellate ( R /r=2.0), arms triangular with blunt tips, armtips upturned. Interradial arcs curved( Fig. 4A, D ).

Abactinal plates mostly hexagonal in shape, variably polygonal to round distally adjacent to superomarginal contact. Individual plates tabulate with broad base. Fasciolar grooves well developed cross all of disk surface ( Fig. 4B ). Each plate with 3 to 30 granules on surface, peripheral granules on radial disk and arm plates two to three times larger than those on central plate surface ( Fig. 4B ). Granules on interradial plates and distally adjacent to superomarginal contact more homogeneous in size. Larger papular radial plates with 35–50 (four to ten, mostly six to eight per side), large trapezoidal peripheral granules different from other coarse round granules. Abactinal plates distributed on disk and approximately midway along arm, the remainder of which occupied by abutted superomarginal plates ( Fig. 4C ). Interradii with closely arranged plates bearing homogeneously sized, closely distributed granules. Papulae present on radial regions, absent interradially. No pedicellariae. Madreporite quadrate in shape, flanked by four abactinal plates.

Superomarginals and inferomarginals, 24 (armtip to armtip), both series offset along complete series forming zigzag contact between them on lateral surface. Superomarginal plates with convex surface and strongly rounded dorsolateral edge, making plate rounded in cross-section. Superomarginal plates wide, almost completely with dorsal-facing with series forming distinct boundary around abactinal surface, occupying approximately 16% of the disk radius “r” (=0.4/2.4). Distalmost five superomarginal plates completely abutted over mid radius with sixth superomarginal plate partially abutted on all arms ( Fig. 4C ). Round abactinal surface of each superomarginal plate bald, smooth, with nearly all granules absent. Lateral side of superomarginal plates with cluster of densely packed, round granules, approximately 15–50, mostly 20–25, with largest number interradially decreasing to approximately 10–15 distally becoming nearly absent near armtip. Superomarginal plates each with 15–30 closely packed quadrate granules forming periphery around each plate. Inferomarginal plates covered by a dense pavement of closely packed round, easily abraded granules, 100–800 completely covering plate surface. Distalmost three to five inferomarginal plates with irregular polygonal to triangular raised, smooth, bald surface. No pedicellariae on either marginal series observed. Terminal plate triangular, half the size of adjacent superomarginal plate.

Actinal plate surface with three to four rows arranged in chevron-like series ( Fig. 4D ). Individual plates quadrate to rectangular in shape with those distalmost interradially adjacent to the inferomarginal plate contact smallest and most irregular in shape. Plates covered by relatively coarse granules, approximately three count along a 1.0 mm line. Individual plates covered by granules, 8– 60 per plate, with granules differing in shape for peripheral and central plate regions with peripheral granules more quadrate versus those on central areas which are more round. All granules evenly but closely spaced. Actinal plates adjacent to the adambulacral plate series rectangular and relatively elongate compared to those occurring on the remainder of the actinal intermediate region. Granular cover becomes more homogeneous distally adjacent to the inferomarginal plate contact. Actinal granules approximately 1.5–2.0 the size of those on the inferomarginal plate surface. No pedicellariae.

Adambulacral plates with furrow spines, 4 to 7, with fewest furrow spines distally, two series of subambulacral thick spines, each with three spines per series and a series of granules, 2 to 4 which are similar in appearance to those on actinal intermediate plate surface ( Fig. 4E ). Furrow spines with blunt, rounded tips, quadrate in cross-section, palmate arrangement with distinct space setting them apart from subambulacral spines. Subambulacral spines, three, each spine quadrate to polygonal in cross-section, approximately twice as thick as an individual furrow spine, approximately 70% of the height of the furrow spines. Third subambulacral series, three to four, short, approximately 50% of height of adjacent subambulacral spine with blunt to pointed tip. similar in height to actinal granules. Oral plates with 9 to 10 furrow spines, with two projecting into mouth per interradius. Oral spines triangular to quadrate in cross-section, with blunt or pointed tips. Oral plate surface with two or three short thick spines, triangular to polygonal in cross-section, similar in appearance to subambulacral spines on adambulacral plates. Fossae between two halves of the oral plate with short, thick spines, similar to the second and third series of subambulacral spines, polygonal to triangular in cross-section. Spines on oral plates all widely spaced.

Color of living individuals was yellow with white highlights along the disk inter radii and around the superomarginal plates ( Fig. 12B ).

Material Examined

Holotype. MCZ 153216 Near Palmyra Atoll, South Pacific Ocean , 5.620168 ° -161.74697 ° 1373 m. Coll. E/V Nautilus 30 June 2019, 1 wet spec. R=4.8 r= 2.4 cm .

Figures

FIGURE 4. Ceramaster palmyra n. sp. MCZ 153216. Holotype. A. Abactinal. B. Closeup abactinal plates. C. Armtip and superomarginal plates. D. Actinal. E. Adambulacral plates with furrow and subambulacral spines. Scale bar=5.0 mm: A, B; Scale bar=1.0 mm: B, E; Scale bar=3.0 mm: C.

FIGURE 12. Ahuastra and Ceramaster palmyra observed in situ. A. Ahuastra kupanaha nov. gen. nov. sp. in situ, showing apparent feeding. B. Ceramaster palmyra n. sp. in situ.