Circeaster pullus, Mah, 2006

Mah, Christopher L., 2006, Phylogeny and biogeography of the deep-sea goniasterid Circeaster (Echinodermata, Asteroidea, Goniasteridae) including descriptions of six new species, Zoosystema 28 (4), pp. 917-954 : 940-944

Circeaster pullus n. sp.

( Figs 6 D-F; 8)

HOLOTYPE. — Hawaiian Islands . Off Kona, Hawaii, 19°37.9’N, 156°02.1’W, 585 m, 18.VII.1996, 1 dry spec., R = 8.8 cm, r = 3.3 cm ( CASIZ 172875 ).

PARATYPES. — Hawaiian Islands. Off Kona, Hawaii, 19°37.9’N, 156°02.2’W, 535 m, 19.VII.1996, 1 dry spec., R = 8.9 cm, r = 3.3 cm ( CASIZ 172876). — Off Oahu, Hawaii, 21°38’N, 158°47’W, 2305.1 m, 16. V.2001, 1 wet spec., R = 6.5 cm, r = 2.9 cm ( CASIZ 163326). — Pinnacle north of FFS, NW Hawaii, 24°34.0’N, 166°1.80’W, 1360 m, 19.IX.2001, 1 wet spec., R = 2.7 cm, r = 1.3 cm ( BPBM W3510).

New Caledonia. South New Caledonia, 23°02’S, 166°52’E, 620-700 m, 30.III.1994 ( MNHN EcAs 11736).

ETYMOLOGY. — The species epithet is “ pullus ” for “young” in honour of its collector, Dr Craig Young ( OIMB).

DISTRIBUTION. — Hawaiian Islands to New Caledonia. 620-2305.1 m.

DIAGNOSIS. — R /r = 2.0-3.0. Abactinal arm plates bare, enlarged, at base of arm. Round, hemispherical granules on disk, marginal plate surface. Superomarginal plates abutted over midline. Enlarged subambulacral spine abradial to adambulacral pedicellaria, adjacent to actinal intermediate region. Bivalve pedicellariae present on actinal surface, adambulacral plates.

APOMORPHY LIST. — Nodes 19 to 18: 4.3, subambulacral accessories few; 7.1, bivalve pedicellariae present.

Nodes 19 to Circeaster pullus n. sp.: 4.2, spine abradial to pedicellariae.

DESCRIPTION

Disk moderately flattened relative to those of other species. Interradial arcs broad slightly curved to linear. Abactinal plates slightly convex, round to polygonal to quadrate in outline. Carinals polygonal, interradials more rounded. Plates moderate sized on central disk region, becoming smaller, more heterogeneous in shape interradially, adjacent to superomarginal plate contact. Abactinal arm plates, two to three times larger than interradial plates, gradually becoming polygonal to oval, enlarged, before superomarginals abut over arm mid-radii. Arm plates similar in size to carinal disk plates.Plates in central region of disk with 1-18, usually 3-10, coarse, scattered granules. Granules most numerous on largest plates on central disk region, attenuating closer to contact with superomarginal plates. Granules absent on plates nearest superomarginal plate-disk contact and interradial regions on disk. Granules strongly convex, bead-like, resting on plate surface. Abundance of granules less in New Caledonia specimen. Granules limited 1-12 per plate only plates proximal to disk centre, adjacent to madreporite, anus, primary circlet. Other plate surfaces bare. Granules in concave pitting. Jaw-like pedicellariae small, less than 1 mm in width with shanks, well-developed. Two or three teeth present in Hawaiian specimens. Pedicellariae larger, with flatter blades, three to five teeth present in greater abundance in New Caledonia specimen.Oblong pits present where pedicellariae are absent. Madreporite pentagonal with relatively deep-sinusoidal folds flanked by six plates.All abactinal plates, madreporite surrounded with a periphery of smaller bead-like accessory granules, approximately 30-40% smaller than those on the abactinal plate surface. Rounded granules, bead-like, 10-50 depending on plate size.

Approximately 35-50 (usually about 40) marginal plates in each interradius (arm tip to arm tip). Marginal plate surface slightly convex, quadrate rounded to angular in cross-section. Spines absent, rounded granules present on all marginal plate surfaces. Approximately 40-100 spaced, rounded to angular bead-like granules, evenly spaced, forming border around each marginal plate identical to those on abactinal surface. Both series of marginal plates largest at interadii, becoming smaller and narrower closer to arm tip. Pedicellariae, three to six, identical to those on abactinal surface, present on lateral and ventral surface of both marginal plate series. The New Caledonia specimen with flatter, broader, toothed pedicellariae versus the Hawaiian specimens with narrower, sugar-tong like morphology.

Approximately 50% of arm, approximately 10-15 distalmost superomarginal plates abutted at midline on arm. Superomarginal plate surface with 3-60 hemispherical scattered granules at plate centre. Granules absent from lateral surface of superomarginal plate adjacent to abactinal disk.Superomarginal plates with linear to low-curved contact with disk. Abundance of granules decreases distally, from c. 50 to absent, adjacent to terminal plate.

Inferomarginals slightly offset from superomarginals. Inferomarginals with 3-60 hemispherical scattered granules. Granular abundance highest interradially, attenuating distally. Granules more abundant on ventral surface adjacent to actinal plates. Granules absent from inferomarginal lateral side and plate surface adjacent to superomarginals. Highly convex to straight contact between inferomarginals and actinal plates.

Actinal regions large, extending to base of arms, corresponding to area of abactinal arm plate enlargement. Plates form three to five irregular chevrons. Actinal plates quadrate to polygonal in shape with more rounded, smaller plates adjacent to inferomarginals. Plate surface with 1-15 (typically 3-10), coarse, scattered, hemispherical granules, an enlarged pedicellaria on bare plate surface.Twelve to 20 larger, peripheral bead-like, granules similar to those on other plates. Surficial and peripheral granules in New Caledonia specimen with roughened tips. Incipient grooves present between peripheral granule borders. Pedicellariae with wide flap-like valves, six to eight teeth on each valve. Single pedicellaria or combination of pedicellariae and granules present on actinal plates.

Adambulacral plates similar in size to actinal plates. Furrow spines four to eight, flattened, oval to angular/triangular in cross-section. Furrow spine abundance highest (seven or eight) near mouth lowest at arm tip (three to six). Adambulacral pedicellariae separated from furrow spines by discrete space. Subambulacral granules large, thick, angular to rounded in cross-section. Adambulacral plates surrounded by 12-15 coarse, angular peripheral granules identical to those on actinal plates. Peripheral granules adjacent to tube foot furrow, angular to triangular in cross-section. Subambulacral surface, peripheral granules in New Caledonia specimen with roughened tips. More discrete spaces separate enlarged subambulacral granules from peripheral granules on adambulacral plates.

Mouth plates flanked by 10-12 furrow spines. First two to three spines on oral plate directed into mouth enlarged, approximatley four times thicker, twice as long than typical furrow spine size. Subsequent mouth plate furrow spines attenuated distally. Mouth plate covered by 20-35 coarse, angular granules. Granules six or seven, enlarged, form border on either side of mouth plate depression, some closely abutting. Other granules are lower, and angular, polygonal in cross-section, evenly spaced. Single pedicellaria identical to those on adambulacral plate present or absent on mouth plate adjacent to furrow spine.

The smallest specimen shows several differences. Abactinal plates limited to the disk, absent from arms, similar in size and shape. Granules, pedicellariae largely absent from abactinal plate surfaces. Individual granules present near disk center.Ten to 30 coarse peripheral granules around each abactinal plate border.

Marginal plates c. 20 per interradii from arm tip to arm tip. C. 70-80 coarse granules form periphery around marginal plates. Seven to eight superomarginals abutted at midline, with slightly jagged contact.Two to six coarse, scattered granules present on superomarginal surface near dorsolateral edge. Inferomarginals with 2-20 coarse scattered granules, one or two paddle-shaped pedicellariae, teethed. Terminal plate approximately three times the size of adjacent superomarginal plates. Actinal surface with two or three chevrons, actinal plates periphery bordered by 6-20 large, angular granules, tips blunt to pointed. Actinal plates with single to few granules resembling peripheral granules and/or paddle-shaped pedicellaria with 8-11 sharp teeth along lateral side of each valve. Pedicellaria uncommon on actinal plates. Remainder of actinal plate surface bare. Six to eight (mostly seven or eight) compressed furrow spines. Adambulacral plate with paddle-like pedicellariae, single enlarged subambulacral spine.

The Hawaiian specimens were recorded in situ as orange. Living colour of the New Caledonia specimen is unknown. In situ observations of C. pullus n. sp. (C. Kelley, HURL, unpubl. data) show the abactinal disk surface substantially inflated.

Circeaster americanus (A. H. Clark, 1916) ( Fig. 7 )

Lydiaster americanus A. H. Clark, 1916: 141 ; 1954: 376.

Circeaster occidentalis H. L. Clark, 1941: 46 , pl. 4, fig. 2. — A. H. Clark 1954: 376.

Circeaster americanus – Halpern 1970a: 265, figs 26- 28; 1970b: 174. — Downey 1973: 47, 55, pl. 21A, B. — Walenkamp 1979: 52, figs 14, 18, pl. 12, figs 1, 2. — Clark & Downey 1992: 237. — Clark 1993: 250.

MATERIAL EXAMINED. — SM joined-variant 1 ( Fig. 7 A-C): Caribbean Sea. Saint Christopher and Nevis, SE of Nevis, 17°06’N, 62°17’W, 322 m. 8.X.1969, 1 dry spec., R = 8.2 cm, r = 3.3 cm ( NMNH E12712). — Netherlands Antilles, North of Saint Eustatius, 17°46’N, 62°59’W, 355-365 m, 18. V.1967, 1 dry spec., R = 7.8 cm, r = 2.8 cm ( NMNH E12798). — Leeward Islands, Dominica, Dominica Passage, 15°38’N, 61°7’W, 808 m, 5.III.1966, 1 dry spec., R = 5.4 cm, r = 2.2 cm ( NMNH E12801). — Off SE coast of Martinique, 14°18’N, 60°45’W, 1235 m, 7.VII.1969, 1 dry spec., R = 3.9 cm, r = 1.9 cm ( NMNH E19072 ). — Caribbean Sea, no other data, 1 dry spec., R = 9.9 cm, r = 4.2 cm ( NMNH E19076 ). — Off East central coast Nicaragua, 13°31’N, 81°54’W, 549 m (300 fms), 12.IX.1957, 1 dry spec., R ≈ 6.5 cm (arm broken), r = 3.2 cm ( NMNH E19077 ). — 24°15’N, 80°02’W, 545 m, 1 dry spec., R = 7.8 cm, r = 3.3 cm ( RSMAS UMML 40.216). — Off Columbia, 10°13’N, 76°6’W, 814-1050 m, 15.VII.1966, 1 dry spec., R = 7.1 cm, r = 2.4 cm ( RSMAS UMML 40.231). — 16°35’N, 80°10’W, 577 m, 18. V.1962, 1 dry spec., R = 9.7 cm, r = 4.3 cm ( RSMAS UMML 40.573). — Off Venezuela, 11°50’N, 66°10’W, 1059 m, 23.VII.1968, 2 dry specs, R = 6.0 cm, r = 2.0 cm, R = 2.5 cm, r = 1.3 cm ( RSMAS UMML 40.574). — Off Suriname, 8°14’N, 57°38’W, 1408 m, 15.VII.1968, 3 dry specs, R = 6.3 cm, r = 2.4 cm, R = 5.1 cm, r = 2.1 cm, R = 4.3 cm, r = 1.6 cm ( RSMAS UMML 40.575).

Florida. SW of Apalachicola Bay, 28°17’N, 86°21’W, 671 m (367 fms), 20. VI.1969, 2 dry specs, R = 8.9 cm, r = 3.6 cm, R = 8.2 cm, r = 3.2 cm ( RSMAS UMML no number).

SM free-variant 2 ( Fig. 7 D-F): Guyana. NE of Georgetown, 8°33’N, 54°18’W, 675-1253 m, 12.VII.1968, 1 dry spec., R = 8.7 cm, r = 3.1 cm ( NMNH E19046 ).

Caribbean. Saint Vincent, off Georgetown 13°21’N, 61°02’W, 708 m, 6.VII.1969, 1 dry spec., R = 8.5 cm, r = 3.5 cm ( NMNH E21156 ). — Quintana Roo, off Espiritu Santo Bay, 18°57’N, 87°9’W, 1143 m (625 fms), 7.VII.1970, 1 dry spec., R = 6.2 cm, r = 1.5 cm ( NMNH E19048 ).

Florida. Straits of Florida, 23°42’N, 80°43’W, 1083 m, 30.IV.1969, 1 dry spec., R = 5.9 cm, r = 1.3 cm (NMNH E19073 ).

DISTRIBUTION. — Tropical Atlantic-Florida, Louisiana, and North Carolina and the Caribbean, including Columbia, the Grenadines, Leeward Islands, Nicaragua, Netherlands Antilles, St. Vincent, Suriname, and Venezuela. Additional specimen records (not examined, NMNH E19052 , E19074 , E19075 ) extend the depth range of this species to 500-1450 m.

DIAGNOSIS. — R/r ≈ 2.4-4.0. Granules round, scattered over abactinal disk, arm surfaces. Arm plates enlarged, bare relative to disk plates; arm plates similar to disk plates in overall size and shape. Superomarginal plates abutted at midline. Row of enlarged subambulacral spines present adjacent to furrow spines. Bivalve pedicellariae present on actinal and adambulacral plates.

APOMORPHY LIST. — Nodes 18 to 17: 6.3, interradial arcs curved; 7.2, paddle-like pedicellariae, absent.

Node 17 to Circeaster americanus -variant 1: 2.3, SM abutted over midline.

Node 17 to Circeaster americanus- variant 2: 4.1, row of enlarged subambulacral spines.

DESCRIPTION

Note on descriptions

As indicated above, full descriptions of adult C. americanus are summarized in Halpern (1970a, b) and Clark & Downey (1992). Several smaller specimens (RSMAS UMML 40.574, R = 2.5 cm, RSMAS UMML 40.575, R = 4.3 cm and NMNH E19072 , R = 3.9 cm) were not included in these earlier studies but display significant information on growth and illustrate size range within the species and are described below.

Smaller specimens

Smaller specimen from RSMAS UMML 40.574 with 21 superomarginal inferomarginals per interradius from arm tip to arm tip, increasing to c. 30 in NMNH E19072 and c. 31-32 marginal plates in RSMAS UMML 40.575. The RSMAS UMML 40.574 specimen shows a continuous or nearly

continuous series of carinal plates from disk to terminal. Plate series on arm, slightly enlarged, convex; becoming smaller, elongate distally. Where carinal series is discontinuous, distalmost superomarginals adjacent to terminal abut at midline. Continuous, discontinuous carinal series varies from arm to arm on a single individual and across different specimens but pattern appears consistent between smaller and larger specimens. In larger individuals where arm carinals absent distally, additional superomarginals abut over midline adjacent to terminal. Marginal plate granules with identical distribution pattern in smaller specimens, with higher granule density interradially decreasing distally, present on all plates, including those adjacent to the terminal. Terminal plates enlarged, with two short spines present. Spines absent in larger specimens with terminal plate comparable in size to adjacent superomarginal plates.Marginal plate patterns suggest an ontogenetic change as carinal plate series along the arm are discontinued proximally followed by subsequent addition of abutted superomarginals distally, in larger individuals (R ≥ 3.5).

Furrow spines in RSMAS UMML 40.574, three or four with a single enlarged subambulacral spine and pedicellariae, immediately adjacent on the adambulacral plate. The slighly larger, RSMAS UMML 40.575 with four or five furrow spines, a variable full row of subambulacral spines or single subambulacral spine and a single enlarged bivalve pedicellaria. Specimen NMNH E19072 shows five or six furrow spines with variable rows or single subambulacral spine.

In situ observations of C. americanus show it as light tan above but off white below with brownred tube feet (D. Pawson, NMNH, pers. comm. 29.VIII.2004).

Figures

FIG. 6. — A-C, Circeaster sandrae n. sp. (MNHN EcAs 11730); A, actinal surface; B, abactinal surface; C, abactinal arm-disk surface; D-F, Circeaster pullus n. sp.(CASIZ 172875); D, abactinal surface; E, abactinal arm-disk surface; F, oral surface. Abbreviations: Ped, pedicellariae; Sub, subambulacral spine. Scale bars: A, F, 0.5 cm; B-E, 1.0 cm.

FIG. 7. — Circeaster americanus (A.H.Clark,1916):A-C, variant 1 (NMNH E19076);A, abactinal surface;B, actinal surface;C, abactinaldisk showing arm tip with superomarginals abutted over midline; D-F, variant 2 (NMNH E19073); D, abactinal surface; E, arm tip showing plates to terminal plate;F, actinal surface. Scale bars: A-C, 1.0 cm; D-F, 0.5 cm.