Astroceramus eldredgei

Mah, Christopher L., 2015, New species, corallivory, in situ video observations and overview of the Goniasteridae (Valvatida, Asteroidea) in the Hawaiian Region, Zootaxa 3926 (2), pp. 211-228 : 217-221

Astroceramus eldredgei . nov. sp.

Figures 2 B–E, 3A–G

Etymology. This species honors Dr. Lucius Eldredge (1938–2013), former Executive Secretary of the Pacific Science Association and scientist at the Bernice P. Bishop Museum in honor of his contributions and support of biology and natural history in the tropical Pacific region.

Comments. Astroceramus eldredgei n. sp. is the second species of Astroceramus , which has been recorded from the Hawaiian region. The other species, Astroceramus callimorphus Fisher 1906 is distinguished primarily by the much more strongly stellate body form (R:r=3.35) in A. callimorphus with longer arms versus the more stout form with shorter arms in A. eldredgei (R:r=1.65–2.08). There are also narrower and more numerous superomarginal plates (n=36 armtip to armtip) in A. callimorphus versus 12–16 in A. eldredgei . Astroceramus eldredgei also has extremely enlarged, round, bulbous subambulacral spines relative to its furrow spines versus those in A. callimorphus , whose subambulacrals are smaller and closer in size to the furrow spines.

Astroceramus eldredgei has fewer superomarginal plates per interradius than any of the other Indo-Pacific Astroceramus spp. as outlined by Kogure and Tachikawa (2009). The Atlantic A. brachyactis displays the most comparable number of superomarginals per interradius (n=18 at R=3.0 cm) relative to A. eldredgei and has very similar bulbous subambulacral spines.

Feeding observations. Two images from off Makapuu Point (M-214-002 and possibly M-379-062) show Astroceramus eldredgei climbing on branches of the blue plexaurid octocoral Astromuricea theophilasi ( Figs 2 D, E). There are several discolored and/or barren regions on the colony, suggesting recent predation. Another image (M-361-016) shows A. eldredgei on what appears to be a white and orange colored Paragorgia ( Fig. 2 C). The localities for the specimens below indicate that nearly all individuals were collected from coral beds or places where potential feeding habitats were present.

Occurrence. Off Makapuu Point, Kaiwi Channel; Oahu, Molokia Channel; South Point and Kona, Big Island; West Pac Bank, NWHI; Cross Seamount 266– 429 m.

Description. Body shape stellate R:r=1.65 (holotype)–2.08 (other variation from paratypes) with short arms (larger individuals tend to show more stellate shape). Disk and arms thick, strongly calcified with straight interradial arcs ( Figs. 2 B, 3A).

Abactinal surface flat. Abactinal plates polygonal, ranging from quadrate to hexagonal in shape ( Figs 3 A,B). Smaller individuals with abactinal plates less polygonal, rounder in outline. Plates in ordered series, with a discrete carinal series. Individual plates more homogeneous, larger proximally becoming smaller and more irregular in size and shape distally, adjacent to superomarginal boundary. Individual plate surfaces smooth with no surficial granules in most. In a minority of specimens (e.g., BPBM W2233) one to four granules, similar to those on the marginal plates is present on either a minority of abactinal plates or on small abactinal plates adjacent to contact with superomarginal series. Most plates with glassy bosses, 80–150, widely and evenly spaced embedded on each plate face in a pattern radiating from plate center ( Fig. 3 B). Glassy bosses more abundant proximally than distally. Oval to spherical shaped granules,10–50 (mostly 20–40) spaced widely and evenly around the periphery of each plate. Tiny paddle-shaped pedicellariae (each valve length=~ 0.8 mm) present on a minority (~10%) of plates. Shallow fasciolar grooves present around plates. Madreporite triangular, flanked by three abactinal plates, with many spherical granules around periphery ( Fig. 3 B). Superomarginal boundary with abactinal plate surface is straight to weakly convex.

Superomarginal plates 12–16 (at R= 3.2–5.2 cm, respectively) per interradius (armtip to armtip) ( Fig. 3 A). Loose correspondence of inferomarginals, 14–20 (at R= 3.2–5.2 cm) per interradius (armtip to armtip). Superomarginals show 1:1 correspondence interradially but show more disjunction distally, especially along the arm. Superomarginals, four to six, butting along radius along arm ( Fig. 3 A, C). Some show 1:1 correspondence but others are slightly offset. One arm on BPBM W2233 (R=5.2) shows pre-terminal superomarginal is triangular but others in type series show typical distal most size reduction of superomarginals adjacent to terminal plate. Superomarginals present on disk (counting only those with a full facing on the disk) ranges from four to six (at R= 3.2–5.2 cm). Both marginal plate surfaces covered with spherical granules, 10–60 (mostly 40–50), widely distributed and present on the raised superomarginal surface. These granules leave tiny, round concavities in their absence ( Fig. 3 C). Other than granules, marginal plates are otherwise bare and smooth. Superomarginal plates quadrate in outline but mound-like in cross-section. Superomarginal surface shows discrete texturing and relatively deep welts. Inferomarginals with granules, 10–150, on plate surface sitting relatively flush compared to those on superomarginals. Lateral surface of superomarginal and inferomarginal plates adjacent to contact between plate series is bare with no granules. Terminal plate is large, triangular. Each marginal plate surrounded by 20–140 (approximately 25/side) granules, identical in appearance to those on the superomarginals. Shallow fasciolar groove present between marginal plates. No pedicellariae observed on marginal plate surface.

Actinal surface with three to four chevron plate series. Individual plates quadrate to irregularly polygonal in shape ( Fig. 3 D, E). Plate surface with coarse, spherical granules, two to 20, widely but evenly distributed ( Fig. 3 E). Peripheral granules, 10–40 (approximately 10 per side), quadrate to round in outline. Paddle-shaped pedicellariae similar to those on abactinal surface variably present on actinal plates ( Fig. 3 F). Some individuals (e.g. BPBM W2192) show a single pedicellariae present on early 40% of actinal plates (11/28) in each interradius whereas on most others, only one or two pedicellariae are present per interradius. Individual plates with peripheral granules, 10–50 (~30 on most) polygonal to quadrate in shape, widely spaced around the periphery of each plate. Four inferomarginals with full facing in each interradius, each with convex contact onto actinal plate region.

Furrow spines, four to six (mostly four or five), blunt, thick, round to quadrate in cross section with central two to three spines thickest and peripheral spines shortest and more slender ( Fig. 3 E,G). Relative to the central spines, the distal most furrow spine is the shortest and smallest. Subambulacral spines, bulbous, large, round and blunt, one to three (mostly one or two), longer, larger, thicker than furrow spine with each subambulacral spine equivalent to two or three furrow spines in thickness. Subambulacral spines flanked by two smaller ones, each <50% in length and comparable to furrow spines in thickness. Remaining adambulacral plate granules, four to 15, round, angular in cross-section with poor distinction from peripheral granules. Adambulacral granules heterogeneous in morphology, with some larger and round in shape, others smaller and more angular. Oral plate with eight furrow spines and one prominent spine, triangular to quadrate in cross-section, projecting into mouth ( Fig. 3 E). Oral plate furrow spines descending in size from largest proximally to smallest distally. Smallest of these oral furrow spines is most similar to furrow spines on adambulacral plates. As with other adambulacral plates, one or two enlarged subambulacral spines is present on the oral plate adjacent to the furrow spines. Oral plate surface with six to 15 granules, widely spaced, angular to quadrate in cross-section. Corresponding angular granules, approximately 10, present along contact with paired oral plate in each interradius. Pedicellariae were not observed on adambulacral plates.

Color in life is a deep orange.

Material examined. HOLOTYPE. BPBM W2334, Off Makapuu Pt., Oahu, Kaiwi Channell, near coral beds. 366 m (1200 feet). (1 dry spec. R=4.3, r=2.6); PARATYPES W1772. Molokia Channel, Hawaiian Islands 266–457 m (200–250 fms), Coll. W.D. Madden, 10 Oct. 1966 (1 wet spec. R=4.4, r=2.4); W2233 Off Makapuu Point, Kaiwi Channel, Oahu, in vicinity of precious coral beds 366 m (1200 ft) Coll. W.D. Madden, Nov 1973 (1 dry spec. R=5.2, r=2.5); W2344 Off Makapuu Point, Kaiwi Channel, Oahu, on precious coral beds, 266 m (200 fms), Coll. W.D. Madden 20 Sept 1973, (1 dry spec. R=4.2, r=2.2) W3523 Makapuu, Oahu, 21º20.289, 157º35.014, 429 m. Coll. Pisces IV, 1 Nov. 2002,P4-071, spec. 3. (1 dry spec. R=4.2, r=2.2); W2192 Off Makapuu Point, Oahu, associated with pink coral. Coll. W.D. Madden, 4 May 1972. (1 dry spec. R=3.3, r=1.9); W2859 Off Makapuu Point, Kaiwai Channel, Oahu, in precious coral beds 266 m (200 fms), Coll. W.D. Madden 28 Feb 1974. (1 dry spec. R=3.6 r=2.1)

Video observations. Makapuu, Oahu: M-068-035 and 0 38. 21.3, -157.55, 367 m; M-152-033. 21.2966, - 157.5433, 384 m; M-214-002. 21.2766, -157.5383, 367 m; M-361-016. 21.21916, -157.545, 373 m; M-379-062. 21.2966, -157.545, 367 m; P4-071-d13-01523, 21.3372, -157.5832 to 21.338, -157.5840, 429 m; P5-435-s2-01313. 21.3419, -157.59086 to 21.3413, -157.59, 350 m; P5-435-s2-11619, 21.33581667, -157.5866, 327m; R-210-d1- 0 5318 and 0 5321. 21.2889333, -157.538666, 376 m. Off Kona, Big Island: R-135-d1-02409. 19.53133, - 155.9966 to 19.5318, -155.9963, 337 m; R-141-d1-02047. 19.359, -155.5389, 387 m. Keahole Pt, Big Island: P5- 707-d4-00812. 19.804416, -156.12578, 382 m. South Point, Big Island: R-211-d1-02630, 18.84705, - 155.6919333. 349 m. Cross Seamount: R-119-d2-00606. 18.7115, -158.25, 389 m. West Pac Bank, NWHI: 23.253, -162.60846, 377 m.

Figures

FIGURE 2. In situ video observations of Goniasteridae. A. Astroceramus callimorphus hunched over prey. B. Astroceramus eldredgei n. sp. on substrate. C. A. eldredgei n. sp. feeding on Paragorgia? D. A. eldredgei n. sp. feeding on the blue plexaurid octocoral Astromuricea theophilasi E. A. eldredgei n. sp. the blue plexaurid octocoral Astromuricea theophilasi F. Calliaster pedicellaris feeding observation.

FIGURE 3. Holotype of Astroceramus eldredgei n. sp. A. Abactinal surface. B. Abactinal plates. C. Closeup of armtip showing abutted superomarginals. D. Actinal surface. E. Closeup of actinal surface showing actinal intermediate region and tube foot groove. F. Close up of adambulacral region, showing furrow spines and etc.