Hippasteria, GRAY, 1840

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, Zoological Journal of the Linnean Society 160 (2), pp. 266-301 : 284-285

HIPPASTERIA GRAY, 1840

Gray, 1840: 279; 1866: 9; Perrier, 1875: 271; (1876: 86); Sladen, 1889: 341; Fisher, 1911: 223; Verrill, 1914: 300; Koehler, 1924: 178; Mortensen, 1927: 88; Dons, 1937: 17; Mortensen, 1940: 125; Djakonov, 1950: 51 ( 1968: 42); Bernasconi, 1963: 15; Bernasconi, 1964: 253; Halpern, 1970a: 183; A.M. Clark & Courtman-Stock, 1976: 63; Clark & Downey, 1992: 246; Clark & McKnight, 2001: 54.

Type species: Asterias phrygiana Parelius, 1768 (with synonym Hippasteria europaea Gray, 1840 as well as all four nominal species included by Gray as synonyms with H. phrygiana ).

Diagnosis: Disk strongly swollen, Arms relatively broad and short. Body often pentagonal to weakly stellate.

Tissue with pulpy texture covers abactinal plates. Shallow fasciolar grooves present. Secondary plates present. Abactinal plates, tightly articulated, polygonal to irregular in outline, flat and platform-like in shape. Carinal series are poorly distinguished. Abactinal spinelets (sometimes granular) forming fringe around abactinal plates. Spines, large, conical, granules often present on abactinal plates.

Large spines present on superomarginal and inferomarginal plates of most taxa. Superomarginal and inferomarginal plates bare, quadrate to rounded in outline at inter-radii with no other accessories other than large spines. Spinelets present on marginal plates. Shallow fasciolar grooves present between marginal plates. Marginal accessories (granules, spinelets, etc.) differentiated into a fringe on superomarginal and inferomarginal plates. Superomarginal plates dorsal-facing in most taxa,

Actinal fasciolar grooves shallow. Large actinal spines and spinelets present. Subambulacral spines large (and thus few in number). Furrow spines large, blunt, and round in cross-section, usually few in number. Enlarged bivalve pedicellariae on raised bases present on body surface.

Included species: *(asterisk denotes fossil taxon) Hippasteria antiqua Fell, 1956 ; H. californica Fisher, 1905 ; Hippasteria colossa Djakonov, 1950 ; Hippasteria derjungini Djakonov, 1950 ; H. falklandica Fisher, 1940 ; H. heathi Fisher, 1905 ; Hippasteria imperialis Goto, 1914 ; Hippasteria kurilensis Fisher, 1911 ; Hippasteria leiopelta Fisher, 1910 ; Hippasteria mammifera Djakonov, 1950 ; Hippasteria nozawai Goto, 1914 ; Hippasteria pedicellaris Djakonov, 1950 ; H. phrygiana phrygiana (Parelius, 1768) , H. phrygiana argentinensis Bernasconi, 1961 ; H. phrygiana capensis Mortensen, 1933 ; H. spinosa Verrill, 1909 ; H. strongylactis Clark, 1926 ; H. tasmanica McKnight, 2006 .

Comments: Hippasteria , the best known genus of the hippasterines, is encountered on shallow, near-shore to deep-sea settings worldwide and includes approximately 19 nominal taxa, many of which are similar in appearance and have overlapping characteristics. Some taxa occur in a continuous distribution over a wide geographical range but show relatively conservative overall morphology. Hippasteria phrygiana , for example, occurs in the North Atlantic off Europe and North America, as well as off South America, South Africa, New Zealand, and in the Southern Ocean ( Clark & Downey, 1992; Clark & McKnight, 2001). The morphologically similar H. spinosa was described by Lambert (2000) as having pelagic, lecithotrophic larvae. If it were to be found that other Hippasteria spp. had lecithotrophic larvae, then long distance dispersal could explain the observed broad geographical ranges. Some species, such as H. imperalis and/or H. nozawai may actually represent very distinct taxa from the H. spinosa and H. phrygiana complexes, but are poorly known and require further study. Further issues pertaining to Hippasteria species complexes are included below in the Discussion.

Biology: Other ecological observations have included interactions with hagfish, which exploit prey captured, but not consumed, by H. phrygiana ( Auster & Barber, 2006) and associations with fish assemblages observed at human-made structures ( Love & York, 2005). Hippasteria has been described as the host to a number of commensals and parasites, including polynoid polychaetes, in H. californica ( Pettibone, 1969) , the ascothoracid crustacean Dendrogaster in H. phrygiana ( Hamel & Mercier 1994) , and the parasitic chlorophyte Coccomyxa astericola in H. phrygiana ( Mortensen & Rosenvinge, 1933) .

Biochemical compounds have been extracted from H. phrygiana ( Burnell, Apsimon & Gilgan, 1986; Levina et al., 2005) and gonad ultrastructure has been studied by Walker (1979).