Glabraster antarctica ( E. A. Smith, 1876 )

Mah, Christopher L. & Foltz, David W., 2014, New taxa and taxonomic revisions to the Poraniidae (Valvatacea; Asteroidea) with Comments on Feeding Biology, Zootaxa 3795 (3), pp. 327-372 : 339-343

Glabraster antarctica ( E. A. Smith, 1876)

Figure 5 A–F

Astrogonium fonki Philippi 1858: 267 (suppressed as per Madsen 1956, Clark & Downey 1992: 208)

Porania antarctica Smith 1876: 108 ; 1879: 275 pl. xvii., fig. 1; Studer 1885: 160; Sladen 1889: 360, pl. lix, fig. 3; Perrier 1891: 107; Ludwig 1903: 22, pl. ii. Figs. 18–20; 1905: 51–53, pl. vi., fig. 1; Koehler 1906: 10; 1911: 27–28; 1912: 66; 1917: 42–43; 1920: 178, pl. xxxiii, figs. 6, 7; 1923: 74; Fisher 1940: 154; Madsen 1956: 27; A.M. Clark 1962: 34; Branch et al. 1993: 46, 60; A.M. Clark 1993: 22; Stampanato & Jangoux 1993: 178, 180; O’Hara 1999: 180; H.E.S. Clark & McKnight 2001: 165; Manjon-Cabeza et al, 2001: 266, 267; Stampanato & Jangoux 2004: 4; Mutschke & Mah 2010: 815.

Porania antarctica antarctica Smith 1876 : McKnight 1984: 142;

Porania magellanica Studer 1876: 459 ; Sladen 1889: 363, pl. 59, fig 5; Barattini 1938: 20 –21, pl.2 (pt)

Porania magelhaenica Studer 1884: 42

Porania glaber Sladen 1889: 360 , pl. 59, figs 1, 2

Porania spiculata Sladen 1889: 362 , pl. 59, fig. 4

Porania antarctica Perrier 1891 : K107–110; Leipoldt 1895: 588; Ludwig 1905: 51, pl. 6, fig. 1; Koehler 1923: 74 –75 (subantarctic); Fisher 1931: 3; 1940: 154–155; Madsen 1956: 27 –28; Bernasconi 1964: 264; 1973: 314–315; Tommasi and Olivera 1976: 89 (key).

Glabraster magellanica A.H. Clark 1916: 122

Porania armata Koehler 1917:43 , pl. 7, figs 3,4,7, 12; Döderlein 1928: 297

Porania antarctica glabra Fisher 1940: 155 ; Madsen, 1955: 14; H.E.S. Clark 1963: 45, pl. 5(5,6); McKnight 1976: 25.

Porania antarctica magellanica Madsen 1956: 28

? Marginaster pectinatus Carrera-Rodriguez & Tommasi 1977: 102 –103

Porania magellanica magellanica Tablado 1982: 96 –100, pl.1, figs 1–3

Porania (Porania) antarctica magellanica A.M. Clark 1984 : fig. 1B; Clark & Downey 1992: 208 –209, fig 34h, pl. 48F–H

Comments on synonymy. Traditional morphology-based criteria have identified the morphological variation (as subspecies) within this taxon throughout its range but none has found widespread acceptance or support. It is argued herein that the available subspecies of Porania (now Glabraster ) antarctica shows no clear morphological delineation across its range and that available subspecies should be entered into synonymy.

Porania antarctica glabra , which was originally described from the Kerguelen and Ross Sea populations, and Porania antarctica magellanica , which was described from the Magellanic region, have been the most enduring of the Antarctic “ Porania ” antarctica subspecies concepts. Scrutiny of original taxonomic concepts and examination of collections from NMNH, CAS and MNHN specimens throughout P. antarctica’s range (Ross Sea, Chile, Antarctic Peninsular region, Indian Ocean, etc.) suggests no clear taxonomic hypothesis or unambiguous morphological boundary for any of the known subspecies.

Sladen (1889) summarized early Antarctic Porania species, including P. glabra and P. magellanica and noted that Studer’s (1876) description for P. magellanica was “short and insufficient” ( Sladen 1889: 363) and was only able to characterize the species as having two “marginal” spinelets per plate. Porania glabra was characterized primarily by the absence of spines from its abactinal surface in addition to the lack of “marginal spines” from the “outer part” of the ray ( Sladen 1889: 361). Koehler (1917) synonymized glabra and magellanica into antarctica , which met with disagreement by Fisher (1940) who supported the retention of glabra . Madsen (1956) supported magellanica as a subspecies encompassing the Chilean population. H.E.S. Clark (1963) also supported usage of glabra , documenting size variation of material from the Ross Sea. Clark and Downey (1992) summarize some of the P. antarctica concepts but ultimately follow Madsen’s (1956) conventions.

P. antarctica magellanica was distinguished primarily on the presence of two spines per marginal plate and the “sparse” spination present on the abactinal surface in conjunction with the notion that a population of this species was associated with the “Magellanic” faunal province ( Sladen 1889, Madsen 1956). Multiple spines on marginal plates occur on specimens from the Ross Sea (e.g., USNM 1081827, 1081947) and a larger sampling of specimens demonstrates a wide variation in abactinal spine density indicating poor morphological support for P. antarctica magellanica as distinct from “proper” P. antarctica , at least based on original concepts outlined by Sladen (1889). The original notion of associating P. antarctica magellanica with the Magellanic region is undermined by the fact that multiple specimens of the P. antarctica magellanica -like morphology have been collected from Bouvet /Marion Island in the South Indian Ocean (MNHN–MD 24, st. 26, prelevement CM 42). O’Hara (1998) also observed P. antarctica from Macquarie Island with prominent abactinal spination, which provides further evidence contrary to a separate “Magellanic” taxon. Moore et al. (2013) provided further insight into connectivity between P. antarctica populations.

P. antarctica glabra was distinguished by the absence of abactinal spination and the absence of spines from distalmost marginal plates by Sladen (1889). P. antarctica glabra was considered a synonym by A.M. Clark (1962). Her treatment is accepted herein.

However, there is potential for undiscovered, possibly cryptic, diversity in this taxon. Bosch (1989) found markedly different modes of reproduction and development in two morphologically similar taxa of Porania (= Glabraster ) antarctica . These kinds of distinctions, in conjunction with COI data, have been the basis for identification of undescribed cryptic species in other cases (e.g., Naughton and O’Hara, 2009) and suggest cryptic species are present within this taxon. Other widely occurring high-latitude asteroid taxa, such as Odontaster validus have also shown previously unrecognized biodiversity (e.g., Janosik & Halanych 2010; Janosik et al. 2011).

Occurrence. Circum-Antarctic and adjacent high-latitude regions. Falkland-Magellan area, north off Chile to about 30°S, Uruguay, and off Argentina to 35°S, South Georgia, the Shag Rocks, South Sandwich, South Shetland and Clarence Islands, the Bellingshausen Sea and Enderby Land, Bouvet, and Prince Edward Islands, Breid Bay, Kerguelen Islands, Terre Adelie to Ross Sea, Macquarie Island, 0–2930 m.

O’Hara (1998: 180) provides a summary of P. antarctica depth occurrence across its distribution. Bathymetric range apparently varies widely within this species.

Description. Body weakly pentagonal ( Fig. 5 F) to strongly stellate ( Fig. 5 E). R/r= 1.51–2.85. Arms, triangular in shape, varying from well-developed and elongate, contiguous with body (e.g., USNM 1081798) to short and emerging abruptly from well-developed disk (e.g., USNM 1081827). Body generally tumescent. Prominent skin overlying abactinal, marginal and actinal surfaces. Plate outlines obscured in wet specimens.

Abactinal plates forming widely-spaced, reticulate pattern ( Fig. 5 A, C, D). Spines present or absent on abactinal plates ( Fig. 5 C,D). When present, spines are prominent and present individually on each plate. Spines, short with thorn-like or blunt tips ( Fig. 5 D), tend to be most prominent on plates where confluences of bands are present but they are also present in several individuals on individual abactinal bands. Some individuals, such as USNM 1081798 fr. McDonald Islands, also possess numerous tiny (1.0 mm) spinelets, widely dispersed, present on all surfaces, including skeletal reticulation and intervening papular regions.

Abactinal skeleton composed of a primary circlet with strongly developed, paired bars in each interradius emerging from/ articulated with each primary disk plate, extending to interradially located superomarginal plates (FigsA, F). A large convergence of abactinal/interradial plates present where the abactinal, interradial and superomarginal plates meet. Radial plates composed of a carinal series with adradial plates emerging from either side of the carinal series in seven to ten paired bands per arm. These adradial bands have, in turn, a series of secondary plates emerging from them, often varying from an ordered regular series demonstrating repeated open, paired spaces to an irregular, highly convoluted network. The reticulated network becomes more tightly knit and densely arranged more distally along the arm, forming an almost imbricate arrangement. Abactinal plates forming transverse bands emerging from the carinal series with direct correspondance to and articulation with the superomarginal plate series ( Fig. 5 C). Numerous other secondary and tertiary abactinal plates present throughout the reticulated network with several transverse bands emerging from the paired interradial plates ( Fig. 5 A, C). Individual plate “bands” composed of elongate plates, overlapping one another at their ends. Each plate variably elongate, some short with length=width, others reach 5–10x the width. Intervening skin-filled regions between reticulated abactinal skeleton with either bare skin, patches of papulae, two to 30, and/or irregularly shaped plates, small but round, one to 30 in number. Extent of papulae to plate occurrence in these regions varies with size of individual, with smaller individuals with more clear skin patches and larger individuals with more papular/plate filled regions. Madreporite round with shallow, well-developed sulci, flanked by three to four abactinal plates.

Marginal series ( Fig. 5 C) composed of of superomarginals, approximately 30–58 (armtip to armtip), 30–50 inferomarginals, (armtip to armtip) at R=0.8 to 7.3. Some individual superomarginal and inferomarginal plates are distinctly different in outline from the other plates ( Fig. 5 C, D). Superomarginal plates imbricate, each flattened with rounded edges, varying from shield-like (distally) to polylobate (proximally). Spines absent from superomarginals, although tiny spinelets are present on some individuals. Interradial superomarginals with most strongly expressed lobes, appearing weakly cruciform. Each superomarginal corresponds directly to one of the adradial plates projecting from the carinal series. Superomarginals become more closely articulated and more strongly overlapping closer to the armtip. Inferomarginals smaller than superomarginals, flattened, varying in shape from oval to elongate and rod-like in shape. Inferomarginals offset from superomarginals, with contact often oriented at an oblique angle to the lower end of the superomarginal plate. Large, flattened, paddle-shaped, blunt spines, one or two present on each inferomarginal plate forming the prominent actinolateral fringe. The actinolateral fringe varies in expression across different individuals. Some display the actinolateral fringe as a simple projection around the edge, whereas in others the fringe is a well-developed shelf present interradially between the arms. Inferomarginals extending away from lateral edge of body to spiny actinolateral edge.

Actinal plates similar in shape to inferomarginals, each plate elongate rod-like in shape forming two (at R= 0.8 cm) to six (at R=7.2) laterally arranged series per interradius, extending from furrow to furrow ( Fig. 5 B). Widest furrow with n=~25 plates from furrow to furrow, with proximalmost series adjacent to oral plates with n=2 to four plates. Smaller individuals (R= 0.8 cm) with two to four irregular series between adambulacrals and inferomarginals. Actinal plates, skin covered, otherwise surficial accessories absent in most (i.e., no granules, no spinelets, etc.). Exceptionally, some individuals with tiny spinelets, two to six per plate. Surface bare. Linear channels continuous present between actinal and inferomarginal plate series.

Adambulacrals “J” shaped in outline, with plate separation varying from direct articulation to skin-filled gap between plates. Furrow spine pointed, narrow, variably one or two, set within the furrow ( Fig. 5 B). Subambulacral spines, one or two, paddle shaped, larger than furrow spines (approximately twice as thick) with blunt tips. Subambulacral tips vary from more widely flattened to strongly cuved (u-shaped in cross section). Oral plates with four to five furrow spines with a single spine projecting into mouth (size at R= 0.8 cm). Oral plate surface without accessories but bearing one or two spines, these blunt, cylindrical. Large skin filled gap present between halves of 2-part oral plate present in each interradius.

Color in life varies from red, pink to orange to “bluish” or “purplish” white, yellow or grey. Actinal surface has been recorded as white, yellow to orange ( H.L. Clark 1963; Mutschke & Mah 2009).

Material examined. Ross Quadrant: USNM 1081811 west of Ross Island, Victoria Land, 77°51’S, 177°33’E to 77°53’S, 177°53’S, 769–770 m, Coll. R/V Eltanin, USARP (2 dry specs. R=5.5, r=3.8; R=4.8, r=3.2); USNM 1081824, Victoria Land, Ross Sea. 73º59’S 170º51’E to 73º58’S, 170º 58’E, 589– 608 m. Coll. R/V Eltanin (1 dry spec. R=4.7, r=3.1). USNM 1081825, Ross Sea. 74º 53’S 175º10’W to 74º52’S, 174º42’W, 2143–2154 m. Coll. R/ V Eltanin (3 dry specs. R=5.5, r=3.5; R=2.3, r=1.5; R=1.8, r=1.0); USNM 1081827 Ross Sea 77º32’S, 172º 32’E 77º31’S, 172º 23’E, 468–482 m, Coll. R/V Eltanin, USARP (1 dry spec. R=4.1, r=3.1); USNM 1081950 Victoria Land, Ross Sea, 75°1’S, 168°23’E, to 75°02’S to 168°32”E, 334–335 m, Coll. R/V Eltanin, USARP (1 dry spec. R=1.5, r=0.6); USNM 1081965 North of Roosevelt Island, 78°29’S, 165°39’W to 78°28”S 165°22”W, 491–493 m, Coll. R/V Eltanin, USARP (1 dry spec. R=3.1, r=1.8); USNM 1081969 Center of Ross Sea, 76°25’S, 170°24’W to 76°25’S 170°32’W, 568 m, Coll. R/V Eltanin, USARP (2 dry specs. R=4.0, r=2.4; R=0.8, r=0.4); USNM 1081944 Victoria Land, Ross Sea, 347–358 m, Coll. R/V Eltanin, USARP (1 dry spec. R=0.9, r=0.4); USNM 1081965 North of Roosevelt Island 78°29’S, 165°39’W, to 78°28’S, 165°22’W, 491–493. Coll. R/V Eltnanin, USARP (1 dry spec. R=3.0, r=1.8). Indian Ocean: USNM 1081798 McDonald Islands, Indian Ocean. 53º04’S, 72º58’E to 53º06’S, 72º57’E. 210– 234 m. Coll. R/V Eltanin (4 dry specs. R=4.2, r=1.8; R=5.6, r=2.0; R=5.7, r=2.0; R=4.7, r=1.7). Magellanic/Peninsular Regions. USNM E3770 Port Churruca, Strait of Magellan, Chile. (1 dry spec. R=2.6, r=1.9). USNM E11507 Strait of Magellan, Brunswick Peninsula, Chile 53º31’S 70º33’W, 270 m, Coll. R/V Hero , USARP (2 dry specs. R=2.2, r=1.0; R=4.6, r=3.0); USNM E38720 SE of Montevideo, Urugay, South Atlantic. 110 m. Coll. R/V Undine. (1 dry spec. R=4.6, r=3.6); USNM E38411 Shag Rocks, Scotia Sea. 53°32’S, 41°47’W to 53°41’S, 42°07’W, 133– 165 m. Coll. USARP (3 dry specs R=6.5, r=3.0; R=6.7, r=2.3; R=7.2, r=3.3); USNM E47652 South Georgia Island, Scotia Sea 53°47, 48”S 37°26’ 2”W, 165–234 m, Coll. J. Dearborn, R/V Islas Orcadas (8 dry specs. R=4.6, r=2.8; R=3.9, r=2.0; R=3.5, r=2.2; R=2.2, r=1.9; R=4.0, r=2.2; R=3.2, r=2.0; R=4.7, r=3.1; R=3.2, r=2.2; R=2.4, r=1.3; R=1.4, r=0.8; R=1.3, r=0.6); USNM E53238 Larrouy Island, Grandidier Channel, Biscoe Islands 65°56’12”S 65° 16’ 42”W, 35–70 m, coll. J. Dearborn, R/V Hero , USARP. (8 dry specs. R=4.2,r=2.4; R=3.9, r=2.2; R=3.6,r=1.9; R=3.5, r=1.4:R=4.6, r=2.1:R=3.3, r=2.4: R=2.5, r=1.7; R=1.8, r=0.9); USNM 1018494 Deception Island, South Shetland Islands 62º58’24”S 60º50’06”W, 110– 137 m. Coll. R/V Hero . (2 dry specs. R=1.3, r=0.7; R=1.5, r=0.7); USNM 1081968 Puerto Basil Hall, Staten Island, Tierra del Fuego, South Atlantic. 54º45’27’S, 64º10’06’W. Coll. R/V Hero . (1 dry spec. R=4.3, r=2.9); USNM 1081800 South Georgia Island, Scotia Sea. 53°51’N 37°38’W to 53°52’S, 37°36”W, 91–101 m, Coll. R/V Eltanin, USARP (5 dry specs. R=4.6, r=2.4: R=3.3, r=1.8, R=3.6, r=1.8; R=2.4, r=1.3 approx. arms curved; R=2.1, r=1.0; USNM 1081802 Cape Froward, Strait of Magellan Chile 53º56’S, 71º15’W to 53º55’S, 71º12’W, 256–320 m, Coll. R/V Eltanin (8 dry specs. R=3.6, r=1.8; R=3.3, r=1.6; R=3.3, r=2.2; R=2.9, r=1.8; R=3.7, r=1.6; R=2.0, r=1.0; R=2.3, r=1.3; R=3.1, r=1.4-note arms/body contorted in many); USNM 1081805 Cape Froward, Strait of Magellan, Chile, 53º39’24”S, 70º55’00”W, 82 m, coll. R/V Hero , USARP (10 dry specs. R=3.3, r=2.0; R=2.5, r=1.4; R=2.2, r=1.3; R=2.5, r=1.3; R=2.6, r=1.6; R=2.0, r=1.0; R=3.8, r=2.0; R=2.3, r=1.4; R=2.6, r=1.5; R=2.6, r=1.5; R=1.7, r=0.9). USNM 1081818 Inutil Bay, Strait of Magellan, Chile, 53º25’18”S, 69º46’00”W, 27–37 m, Coll. R/V Hero , USARP (3 dry specs. R=4.3, r=2.5; R=4.4, r=2.6; R=3.3, r=1.7). USNM 1081822 Strait of Magellan, Chile, 53º30’S 69º48’W, 22–26 m, Coll. R/V Hero , USARP (6 dry specs. R=4.1, r=2.7; R=2.7, r=1.7; R=3.9, r=2.0; R=2.9, r=1.8; R=2.6, r=1.3; R=1.2, r=0.6). USNM 1082737 Inutil Bay, Strait of Magellan, 53º24’30’S, 69º38’30”W, 7–9 m, Coll. R/V Hero . (6 dry specs. R=5.1, r=3.0; R=5.0, r=3.0; R=4.3, r=2.3; R=4.4, r=2.5; R=4.0, r=2.8; R=3.7, r=2.5). USNM 1082910 Clarence Island, Strait of Magellan, 53º51’S, 71º36’W to 53º50’S, 71º41’W, 256–269 m, Coll. R/ V Eltanin, USARP (6 dry specs. R=2.9, r=1.6; R=3.3, r=1.4; R=3.2, r=1.8; R=2.8, r=1.3; R=3.1, r=1.6; R=2.9, r=1.5). USNM 1119614. South Atlantic, 61º12’S 54º 43’W, 240 m. Coll. Moss Landing Marine Labs (1 dry spec. R=2.3, r=1.2); USNM 1136790 N. Lemaire Channel, 200–240 m, Coll. University of Maine. (2 dry specs. R=1.2, r=0.5; R=0.7, r=0.3).

Figures

FIGURE 5. Glabraster antarctica USNM 1081800 South Georgia Island, Scotia Sea (R = 4.6). A. Abactinal surface. B. Actinal surface. C. Dorsolateral showing transverse abactinal plates and marginal plate series. D. USNM 1081968 Dorsolateral showing abactinal spines and marginal plate series (R = 4.3). E. USNM 1081798 McDonald Islands. Abactinal surface (R = 5.6). F. USNM 1081827 Ross Sea (R = 4.1).