Porania pulvillus O.F. Muller 1776

Porania pulvillus (O.F. Müller 1776)

Figure 6 A–F

Asterias pulvillus O.F. Müller 1776: 234; 1788: 19, pl. 19

? Asterias equestris Templeton 1836: 237 (non A. equestris Linnaeus 1758).

? Asterina pygmaea Verrill 1878: 372; 1879: 14

Goniaster templetoni Thomson in Forbes 1839: 118, pl. 4, figs. 1, 2; Forbes 1841: 122

Porania gibbosa Gray 1840: 288; 1866: 16

Porania grandis (pt) Verrill 1885: 542, figs 45, 45a

Asteropsis pulvillus Müller & Troschel, 1842: 64, 128; Lütken, 1857: 71; M. Sars, 1861: 44; Perrier, 1869: 94.

Asteropsis ctenacantha Müller & Troschel 1842: 63; Perrier 1869: 94

Porania insignis Verrill 1895: 138 –139; 1915: 70 (footnote); Gray et al 1968: 152 –153, fig. 28; Gosner 1971: 581; Franz et al 1981: 397, 398;

Porania pulvillus Norman 1865: 122; Perrier 1875: 280 (1876: 96); Viguier 1879: pl. 13, figs. 11–15; Sladen 1889: 360; Bell 1891: 3; 1893: 79, pl. 10, figs. 7, 8; Herdman 1895: 69; Perrier 1896: 43; Pearcey 1902: 309; Simpson 1903: 40; Grieg 1907: 34; Koehler 1909: 99; Faran 1913: 16; Grieg 1913: 115; Gemmill 1915: 10, 21, pl.1, fig. 1; Koehler 1921: 41, fig. 30; 1924: 152; Mortensen 1924: 57, figs. 22, 23; 1927: 90, figs. 51, 52; Rivera 1930: 104, fig. 3; Einarsson 1948: 11; Tortonese 1955: 680; Madsen 1959: 169, fig. 6; Jangoux 1982: 149, 151, fig. 4; Gage et al. 1983: 281; A.M. Clark 1984: 42 (pt.); Clark & Downey, 1992: 209; Metaxas & Davis 2005: 1381; Kirby & Lindley 2005: 454 (larval records); Serrano et al. 2011: 429 (checklist).

Porania (Porania) pulvillus pulvillus A.M. Clark 1984: figs. 2B, 5C, 7b, 17A–C, 18A, B; Clark & Downey 1992: 207, 209

Porania (Porania) pulvillus insignis A.M. Clark 1984: 47

? Poranisca pygmaea Verrill 1914b: 19

Type notes. Clark and Downey (1992: 211) indicated a USNM lectotype and three paralectotypes, along with two further paralectotypes at the British Museum for P. insignis. This, however, contradicts Ahearn (1995: 26) who listed the lectotype and 28 paralectotypes (i.e., 26 more than indicated in Clark and Downey 1992). Additionally, at least two of these lots, USNM 7698 and 6349 are correctly identified as Poraniomorpha hispida, having been misidentified as Porania insignis Verrill 1895.

Taxonomic comments. Synonymy of P. pulvillus insignis: Verrill (1895) did little to justify the separation of P. insignis as a separate taxon from P. pulvillus (Müller 1776). Only Clark and Downey (1992: 211) provided clear delineation of P. insignis from P. pulvillus; these authors argued that P. insignis had a more open abactinal skeleton with mesh area exceeding plate area in larger specimens and with scattered spines present on the actinal surface. However, these characters do not consistently serve to separate the different indicated taxa. In at least one lot (USNM E50125), there is an individual specimen with both an open reticulate skeleton and a closed, densely arranged skeleton, while others show a more intermediate state between “densely arranged” and “open reticulate” skeletons. The presence of this intermediate state is observed in several individuals from the same locality.

It is argued that character differences between pulvillus and insignis are based on individual variation and/or preservation artifacts. Observation of multiple specimen lots shows more open mesh present in those specimens preserved with fully tumescent coeloms (e.g., Paralectotype USNM 6385, USNM 10552, USNM E08391) versus those with more densely crowded abactinal skeletons (E50124) with collapsed body coeloms. Furthermore, Hayne and Palmer (2013) showed that subspecies morphological variation in the intertidal Pisaster ochraceus was attributed to phenotypic adaptation to hydrodynamic activity in the environment. Collection stressors, environmental variation and sheer chance may have also contributed to character variation historically used to distinguish subspecies.

Implicit in the morphological separation between P. pulvillus insignis and P. pulvillus has also been an arbitrary distinction between east Atlantic (North American) and west Atlantic (European) populations as two distinct subspecies (e.g. Clark & Downey 1992). As indicated above, morphological distinctions between subspecies were not well-defined and the morphological basis for separation is weak. Specimens that fall within the definition of P. pulvillus are readily identified from the west Atlantic (North America, e.g., USNM E50124, 10552), whereas those individuals that fall within the range of P. pulvillus insignis are recorded from the east Atlantic (e.g., USNM E08391 from Scotland).

In addition to these comparisons, at least two paralectotype specimens examined by Verrill are actually specimens of Poraniomorpha suggesting that the “open skeleton” used to distinguish pulvillus from insignis by Clark and Downey (1992) may have been, at least in part, inferred from misidentified material. It is unclear if Downey, Ahearn or A.M. Clark designated these paralectotypes.

Occurrence. North Atlantic Ocean. Eastern Atlantic from Trondheim fjord, Norway to the Skagerrak, North Sea, Shetland Islands and NE Scotland west to Lousy Bank (SW of the Faeroes) and south in the Bay of Biscay to N. Spain. On the Western Atlantic from Nova Scotia to Gulf of Maine south to Cape Hatteras, also Lydonia and Baltimore Canyon. 5– 970 m.

Description. Body weakly stellate R/r=1.5–2.4. Clark and Downey (1992) report a mean R/r of 1.81 in 24 specimens with R>3.0 cm. R up to 7.5 cm. Disk tumescent, rays triangular in outline. Interradial arcs rounded (Figs 6 A, C). Abactinal, marginal and actinal surface overlain by a thick layer of skin obscuring plate boundaries in wet or certain dried specimens. Skin appears to be more well-developed in deeper-water specimens (e.g., USNM E30689, E30687, E30690). Pedicellariae not observed.

Abactinal skeleton with round, cylindrical and irregularly lobate or polygonal shaped plates. Some (e.g. USNM paralectotype USNM 6385) show a widely spaced reticulate skeleton (e.g fig. 6D), whereas others showing a densely packed, imbricate skeleton (Fig. 6 A, F) (e.g., USNM E46649) and/or intermediate character states between these two extremes (e.g., E08391, E50125) with both imbricate and open reticulate skeletons present on a single individual. Although distribution of arrangement varies, plate patterns are consistent in most specimens. Reticulations composed of a central round or polygonal plate with three to five radiating bands, composed of overlapping plates (Fig. 5 C,D). Papular pores with one to ten pores per region, which are confluent in many of the specimens observed. Open spaces between mesh often include quadrate to irregularly shaped plates present within the patch framed by the reticulate skeleton. Papulae occur throughout these regions flanking the plates. Papulae absent interradially. The more imbricate or close-knit the skeleton is the fewer papulae are observed. Tight knit skeletons with an imbricate, shingle-like appearance (Fig. 6 F). A series of paired abactinal plates bisects each interradius on the disk extending from the primary circlet to the superomarginal contact (Fig. 6 A). The surface of this interradial bisector is covered by skin but papulae are absent. Abactinal surface in adults devoid of accessories or other structures, but smaller specimens (R=0.5) show single spines present on plate surface [as indicated by Clark and Downey (1992)]. Anus is encircled by spines, 7–15. Madreporite polygonal to round, flanked by two to five irregularly shaped plates always sitting on the interradial bisector.

Marginal plates wide, each plate oblong to crescent shaped (Fig. 6 E). Individual plates interrupted by overlying skin. Superomarginals number 16–36 per interradius (at R=0.5 to 4.7). Inferomarginals similar in shape but more strongly oblong, staggered from superomarginals, forming prominent actinolateral fringe. Individual plates largest interradially, becoming smaller and simpler in shape distally. Each inferomarginal with one to five short, blunt, cylindrical, skin-covered spines on the actinolateral edge. Highest number of spines interradially, but decreasing distally and sometimes lost on distalmost inferomarginals. Individuals from deeper water in the east Atlantic show only one spine per inferomarginal (USNM E30689, E30687, E30690). Skin obscures boundaries between marginal plates and spine articulation with plates. One to three intermarginal papulae present between marginal plates. On individuals with more imbricate or closed skeletons or smaller specimens (R=~1.0), only a single papulae occurs between plates.

Actinal surface flat. Actinal plates quadrate to rectangular arranged in three to six regular series, which are aligned in a pattern consistent with the inferomarginals (Fig. 6 B). Actinal surface in adults is devoid of accessories or other structures, covered by thick skin in most although some individuals possess a single spine on distal plates adjacent to the inferomarginals. As indicated in Clark and Downey (1992) single spines occur on the surface of actinal plates on tiny specimens (R= 0.5 cm). Fasciolar channels present from marginals and along actinals extending to adambulacrals, apparently more well developed in individuals with those with thicker skin layers (e.g., USNM E30689).

Adambulacrals covered by thick skin, interrupting direct contact between plates. Furrow spines, one or two, typically two. Single subambulacral spine. More distal plates with second adambulacral spine forming transverse series with the first and the furrow spines (Fig. 6 B). All furrow spines ensheathed by thick skin. Apical spines on oral plates webbed together. Furrow spines, two to three on oral plates unwebbed, free-standing.

Color in life is deep red, purple to orange. Oral surface is white.

Material examined. West Atlantic (North America). USNM E46642 Off southwestern part of Browns Bank, Nova Scotia 42º32’N 66º25’W, 229 m. Coll. R/V Albatross IV (1 dry spec. R=6.1, r=3.2); USNM E46644 Off southern part of Browns Bank, Nova Scotia. 42º12’N, 65º28’W, 113 m, Coll. R/V Albatross IV (2 dry specs. R= 2.2, r=1.0; R=2.4, r=1.0); USNM E46649 South of Browns Bank, Nova Scotia. 42º13’N 65º42’W, 229 m. Coll. R/V Albatross IV (5 dry specs. R=4.0, r=1.8; R=2.5, r=1.4; R=2.1, r=1.1; R=1.9, r=1.0; R=1.9, r=0.9); USNM E46650 South of Browns Bank 42º16’N 65º44’W, 216 m. Coll. R/V Albatross IV (2 dry specs. R=2.2, r=1.2: R=4.9, r=2.4); USNM E46701 South of Browns Bank, Nova Scotia 42º02’N 65º47’W, 256 m. Coll. R/V Albatross IV (2 dry specs. R=4.3, r=2.5; R=2.8, r=1.6); USNM E30687 Lydonia Canyon 40º21’40”N 67º39’51”W, 818 m, Coll. R/V Alvin (1 dry spec. R=5.6, r=2.8); USNM E30689 Lydonia Canyon 40º21’52”N 67º39’31”W, 607 m, Coll. R/V Alvin (1 dry spec. R=5.0, r=2.9); USNM E30704 Baltimore Canyon 38°9’39”N 73°48’13”W, 307 m. coll. DSRV Alvin (1 dry spec. R=6.9, r=3.0); USNM E30690 Baltimore Canyon 38°9’56”N 73°51’46”W, 500 m. coll. DSRV Johnson Sea Link (1 dry spec. R=5.7, r=3.1); USNM E50124, North of Cape Hatteras, North Carolina. (5 dry specs. R=3.7, r=1.5; R=3.9, r=2.1; R=4.5, r=2.5; R=3.7, r=2.7; R=3.0, r=1.0); USNM E50125 East of Virginia Beach, North Atlantic. 36°40’N 74°40’, 335 m. Coll. RV Columbus Iselin. (3 dry specs. R=4.5, r=2.6; R=4.0, r=2.2; R=4.1, r=2.2). USNM 18496 Paralectotype- Porania insignis, Norfolk Virginia. 37º03’20”N, 74º31’40”W, 190 m. (1 dry spec. R=0.9, r=0.5 and fragments). East Atlantic (Europe). USNM 0 8391 Millport, Firth of Clyde, Scotland. Coll. J.L. Parkhurst. (1 dry spec. R=4.1, r=3.3); USNM E15952 Bay of Biscay, 47°40’N, 5° W, 119 m. Coll. J. Allen, WHOI. (1 dry spec. R=3.0, r=2.5); MNHN no #. Celtic Sea 51º22’N, 11º 42’W, 738– 803 m. Coll. Cosel aboard N. O. Thalassa, PROCELT 1, st. K 196 (1 dry spec. R=4.9, r=3.7) MNHN no #. Celtic Sea 51º48’N, 11º 37’W, 304– 307m. Coll. Cosel aboard N. O. Thalassa, PROCELT 1, st. K 19 (1 dry spec. R=4.1, r=2.5). MNHN no #. Gofe de Gascogne 44º07’N, 4º04’W, 590– 970 m. coll C. Cabioch aboard N. O. Thalassa st. W393 (1 dry spec. R=3.1, r=1.8) (arms upturned)