Gilbertaster FISHER 1906
Creators: name: Mah, Christopher
name: Nizinski, Martha
name: Lundsten, Lonny
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Asteroidea
Valvatida
Goniasteridae
Gilbertaster

description: GILBERTASTER FISHER, 1906   
Fisher, 1906: 1062; McKnight, 1973: 192; Mah, 1998: 66; H.E.S. Clark & McKnight, 2001: 49  
 Type species: Gilbertaster anacanthus Fisher, 1906.   
 Included species: G. anacanthus Fisher, 1906; G. caribaea (Verrill, 1899).   
 Diagnosis: Arms triangular, broad to tapering, narrow (Fig. 3A, E). Disk weakly swollen (Fig. 3A, E).   
Tissue thick, pulpy covering abactinal, marginal, actinal plates. Abactinal plates low, polygonal covered by one to 12, closely articulated angular granules (Fig. 3A– C, E–G) elongate to round in length, flattened, forming smooth to rough surface texture. Fasciolar grooves shallow. Secondary plates present between abactinal plates (Fig. 3C). Abactinal plates with angular accessories (Fig. 3A–C). Pedicellariae large, bivalved with smooth valves, the length of one to two plates and abundant on abactinal surface (Fig. 3B, C).  
 Marginal plates, 50–70 per inter-radius (armtip to armtip), squarish in outline with rounded edges, completely covered by angular granules similar to those on abactinal surface. Variable surfaces smooth (on G. anacanthus) to roughened (on G. caribaea). Pedicellariae large, bivalve (Fig. 3C) similar to those on abactinal surface on marginal plate surface, often bisecting the width of the plate. Spines absent from superomarginal and inferomarginal plate series (Fig. 3A, C, E). Granules, densely arranged, covering superomarginal and inferomarginal plate series complete (Fig. 3A, B, C, E). Superomarginal and inferomarginal plates quadrate at inter-radius (Fig. 3C, E). Fasciolar grooves on marginal and actinal surfaces absent. Fringe of accessories on marginal plates poorly differentiated. Superomarginal plates forming prominent dorsolateral fringe (Fig. 3A, E).   
Actinal plates covered by one to 15 flattened, polygonal, angular granules. Large bivalve pedicellariae similar to those on abactinal, marginal plate surfaces abundant on actinal plates. Actinal plates with granules, but lacking large spines or spinelets (Fig. 3D, G). Pedicellariae, bivalved, present on plate series at perpendicular angle (Fig. 3A–G), adjacent to ambulacral furrow. Pedicellariae, flat-tong shaped with serrated blades present on actinal plates (Fig. 3D, F). Pedicellariae very abundant, present on raised bases (Fig. 3A–G).  
 Furrow spines two to four (usually three) blunt, thickened spines, horizontally flattened (G. anacanthus) to triangular/quadrate in cross-section (G. caribaea) (Fig. 3D, G). Subambulacral spines, one to four, blunt, flattened (Fig. 3D, G). Round to quadrate (G. anacanthus) to triangular in cross-section (G. caribaea). Pedicellariae, bivalved, enlarged on first adambulacral (similar to others) replacing subambulacral spination (Fig. 3D, G) and sometimes replacing furrow spination. Subambulacral spines smaller in size, more abundant (Fig. 3D, G). Furrow spines round in cross-section, not compressed.   
Oral plates covered by ten to 20 flattened, angular, closely articulated granules (Fig. 3D, G), sometimes with enlarged bivalve pedicellariae. Oral plate furrow spines, typically five, flattened to oval in cross-section. Oral region concave (Fig. 3D, G).  
 GILBERTASTER ANACANTHUS FISHER, 1906   
FIGURE 3E–G  
 Fisher, 1906: 1063; A.M. Clark, 1993: 223; H.E.S. Clark & McKnight, 2001: 49 (as Gilbertaster anacanthus)   
 McKnight, 1973: 192; A.M. Clark, 1993: 223 (as Gilbertaster brodiei)   
 Occurrence: Hawaiian Islands, Palau to New Zealand. 277–868 m.   
 Material examined: HOLOTYPE: USNM 21168, Malae Point, Hawaii, 20°6′N, 155°59′W, 463–699 m, coll. USFC Albatross, 11.vii.1902 [1 wet spec. R = 6.5, r = 2.2]; CASIZ 159079, off Kona, 19°38′N, 156°2′W, 670.0 m, coll. Sandra Brooke & Michelle Wood on R/V Pisces V, 14.xii.2001 (1 wet spec. R = 7.3, r = 2.2); CASIZ 159080, Off Kona, 19°38′N, 156°2′W, 868.0 m, coll. Sandra Brooke & Michelle Wood on R/V Pisces V, 14.xii.2001 (1 wet spec. R = 5.2, r = 2.2); CRECH 129, Mutremdu, Palau, 7°16′N, 134°31′W, 277.3 m (910 ft), coll. P. Colin aboard Deep Worker submersible, 6.iii.2001 (1 wet spec. R = 9.9, r = 3.2).   
 Description: Arms five. Disk broad, arms long, narrow (R: r = 2.26–3.0), distinct from disk.   
Abactinal plates tightly abutted, covered by granules, one to six, round to irregularly polygonal to oblong to elongate in outline, forming angular fringe around each (Fig. 3E, F). Carinal series distinct (Fig. 3F). Granules slightly convex to rounded but low and close to disk surface (Fig. 3E, F). Periphery of plate surrounded by four to 12 elongate to roundedpolygonal granules that sit in low concavities on each plate. Plates larger proximally but becoming smaller distally at contact with superomarginal border. Madreporite pentagonal, with well-developed sulci. Secondary plates present but few. Pedicellariae bivalve large (~1.0– 1.5 mm in length) and present in irregular cluster all across the abactinal disk surface. Apparently more common on disk but also present in less abundance on distal arm surface. Papulae present radially, absent inter-radially.  
Marginal plates quadrate in shape, 18–22 in number (superomarginals and inferomarginals identical in number and appearance), largely flat but weakly convex and covered with granules, 20–70, flush, close-set, convex granules, forming a weakly expressed border around the disk periphery. Marginal plate surface more flattened inter-radially becoming more rounded and more convex distally. Granular covering angular, crowded but other major ornamentation (i.e. spines, etc.) absent from marginal plate surface. Granules form weakly differentiated periphery around marginal plate surface. Marginal fascioles absent (Fig. 3E, F). Superomarginal plate surface with dorsol facing (Fig. 3E), especially on distal arm segment. Pedicellariae, bivalved, uncommonly present on marginal plate surface.  
Actinal plates, very tightly articulated, quadrate to rounded in shape, forming three distinct chevrons on actinal intermediate surface (Fig. 3G). Granules present, four to 16 in number, closely abutted and polygonal-oblong to irregular, rounded with low convex appearance in shape (Fig. 3G). Granular cover on actinals flush with those on adjacent inferomarginal plate series. Actinal plate series adjacent to adambulacral plate series each with one enlarged bivalved pedicellariae, decreasing in size proximally to distally, each one flanked by a granular ring, four to 12, enlarged, quadrate (Fig. 3G). Pedicellariae, bivalve, enlarged (~1.0 mm in length), present on several actinal plates, each surrounded by ring of enlarged quadrate granules.  
Adambulacral plates quadrate. First adambulacral with giant pedicellariae, bivalved, smooth on each inter-radius, flush with furrow margin, extending the whole length of the plate (Fig. 3G). Furrow spines, two or three, horizontally flattened, oval in cross-section, becoming reduced to a granule distally. Some adambulacral plates with spines, subequal and very small. These latter spines are observed in conjunction with subambulacral pedicellariae. Subambulacral armature varies. Plates covered by granules, four to six, prismatic to quadrate in crosssection in irregular rows (Fig. 3G). Small granular row present between adambulacrals and proximal actinal plate series. Other plates with large bivalve pedicellariae.  
Oral plates slightly convex with furrow spines, five to six triangular in cross-section, largest proximally. Oral plate surface covered by granules similar to others, large, polygonal, flattened, five pairs on each plate.  
Colour in life is dark orange to yellow. Fisher (1906) notes one specimen as ‘Dull yellow on dorsal surface, brightest on marginal plates, central part of dorsal area with a brownish cast. Actinal surface a pale Naples yellow with a brownish suggestion’.  
 Habitat description: This species has been observed in situ by the Hawaiian Undersea Research Laboratory (HURL) as solitary individuals on soft substratum among round basaltic rocks (C. Kelley, HURL pers. comm., 2009).   
 GILBERTASTER CARIBAEA (VERRILL, 1899) COMB. NOV.   
FIGURE 3A–D  
 Verrill, 1899: 174, pl. 28; Halpern, 1970a: 190; Clark & Downey, 1992: 246 (as Hippasteria caribaea)   
 Occurrence: Known from Cumberland Island, Georgia, Savannah Banks, Stetson Banks, off Jacksonville, FL, and off the coast of West End, Grand Bahama. 500–805 m.   
 Material examined: HOLOTYPE: USNM 18425, Cumberland Island, Georgia, North Atlantic Ocean, 30°58′N, 79°38′W, 538 m, coll. USFC Albatross, st. 4041, 5.v.1886 (1 dry spec. R = 1.8, r = 1.0); USNM 1126236 Jacksonville Lithoherms, 30°31′N, 79°39′W, 553 m, coll. K.J. Sulak, JSL 4683, 10.vi.2004 (1 dry spec. R = 7.7, r = 3.2); USNM 1124498, Savannah Banks, 31°44′N, 79°05′W, 500 m, coll. S.W. Ross, JSL 4687 12.vi.2004 (1 wet spec. R = 5.9, r = 2.8); USNM 1126239 Savannah Banks, 31°46′N, 79°12′W, 509 m, coll. C. Morrison, JSL 4905, 30.x.2005 (1 wet spec. R = 13.3, r = 5.1); USNM 1126238 Stetson Banks, 31°50′N, 77°36′W, 694 m, coll. T. Casazza, JSL 4699, 18.vi.2004 (1 wet spec. R = 4.3, r = 2.6); MCZ 3806, Florida, off Jacksonville, 796–805 m (435– 440 fathoms), coll. Atlantis St. 3782 (1 dry spec. R = 10.2, r = 3.4). NSU no #. Off coast of West End, Grand Bahama. 27°04′N, 79°19′W, 604 m. JSL II 3698, coll. C. Messing. (1 wet spec. R = 5.0, r = 2.3).   
 Description: Arms five. Disk broad, arms short (R: r = 2.1–2.4) distinct from disk (Fig. 3A).   
 Abactinal surface covered by coarse granules, densely packed with no plate surface visible. Granules forming continuous cover, nearly contiguous with superomarginal plate series (Fig. 3A, B). Plates, each with one (exceptionally two or more) large round, tubercular granule(s), surrounded by three to six smaller rounded coarse granules (Fig. 3C). Abactinal plates closely abutting (Fig. 3B) in adult specimens, somewhat less so in smaller individuals (when R = 4– 5 cm). Papulae single, distributed over most of abactinal surface but absent from narrow triangular area adjacent to contact with superomarginal plate series. Madreporite round with well-developed sulcae, surrounded by 12–15 plates. Pedicellariae large (0.8– 2.0 mm in length), bivalve equivalent to three to six granules in relative length evenly distributed over abactinal surface (Fig. 3B, C).   
 Marginal plates elongate [length (L)> width (W)], largest inter-radially, becoming more equal in size and smaller distally. Marginal plates 40–50 per interradius (counted from armtip to armtip) covered by densely packed coarse granules (20–60 per plate) similar to those on abactinal surface. Granules more evenly spaced, less dense in smaller individuals (R = 4–5 cm). Plate surface not visible on inter-radial plates with smooth, bare patches present near arm terminus. Granule shape varies from round, hemispherical to polygonal to more oblong (Fig. 3C). Superomarginal granules prominent, strongly convex, not forming even surface with other granules (Fig. 3C). Granules on inferomarginal plates more polygonal, forming close pavement. Pedicellariae absent from marginals on paratype (smaller specimen) but present on holotype (larger specimen) where they bisect the entire width of superomarginal and inferomarginal plates. Distinct groove present around inferomarginal plate contact with actinal intermediate plate surface.   
Actinal plates forming irregular chevron-like pattern. Actinal plates adjacent to adambulacral plates all with enlarged bivalved pedicellariae equal to length of plate on which it sits. Approximately six to seven granules flank each valve of these pedicellariae. Largest centrally becoming smallest near the ends of each pedicellariae. Other actinal intermediate plate chevron series more irregular with approximately 60% of plates bearing a large bivalve pedicellariae (Fig. 3D). Holotype with nearly all plates bearing a large bivalve pedicellariae. Remaining plates covered by four to 14 (mean of nine) granules. One enlarged, convex granule, flanked by four to seven smaller polygonal granules, varying in size. Pedicellariae present closest to mouth and tube foot furrows becoming almost completely absent on plates adjacent to inferomarginal plate series.  
Furrow spines, thick, triangular to round-oblong rectangle in cross-section, two to three per adambulacral plate with fewer spines on distal plates (Fig. 3D). One large thick (3–4 ¥ thickness of furrow spines), angular, subambulacral spine, present immediately behind furrow spines. This large subambulacral spine flanked by one to two smaller spines, triangular in cross-section, roughly half the height of the large subambulacral (Fig. 3D). Several thickened, blunt granules, polygonal-triagonal in crosssection, five to nine adjacent to the subambulacral spine, similar in size to those on actinal surface. Typically, one enlarged, round granule present adjacent to subambulacrals with other granules irregularly trailing off in size. Distinct groove between adambulacral plates and first adjacent actinal intermediate plate (which bears the large bivalve pedicellariae).  
Enlarged triangular spines two, present on oral plate surface projecting into mouth, adjacent to four thick, polygonal spines on the side of each oral plate (Fig. 3D). Oral plate covered by two enlarged subambulacral spines, round to triangular in cross-section, three to four times as thick as the adjacent furrow spines. Smaller, lower polygonal granules, five to seven present on oral plate surface adjacent to enlarged pedicellariae adjacent to the mouth.  
Colour in life is yellow-orange.  
 Biology: Hippasteria (= Gilbertaster) caribaea was measured for reflectance in a bioluminescence study presented by Johnson (2005).   
 Habitat description: Specimens provided by M. Nizinski were observed as solitary individuals collected on soft substrata. No other organisms were observed at the collection site.
description: Published as part of Mah, Christopher, Nizinski, Martha & Lundsten, Lonny, 2010, Phylogenetic revision of the Hippasterinae (Goniasteridae; Asteroidea): systematics of deep sea corallivores, including one new genus and three new species, pp. 266-301 in Zoological Journal of the Linnean Society 160 (2) on pages 270-274, DOI: 10.1111/j.1096-3642.2010.00638.x, http://zenodo.org/record/10114738