Flat body. Prominent marginals; the supero- and inferomarginals are similar. The aboral plates are flat or paxilliform, bearing granules, low stumps or spines. Only the radial areas have papulae. Pedicellariae are generally present. The tube feet have suckers.
Pseudarchaster alascensis has marginal plates in a continuous band around the perimeter of the aboral surface, and the joints between plates are ill-defined. It is reddish-orange aborally and paler on the oral side. Its five arms can grow up to 10 cm long. The ratio of arm to disc is from 2.6 to 4.0. The aboral tabulate plates are small and hexagonal, forming a relatively smooth surface. Each plate is topped with 15 to 22 granules and has 6 papulae around it. P. alascensis has 33 to 58 superomarginals that encroach well onto the aboral surface, but the individual plates are not well defined. Compact hexagonal granules cover each plate. The corresponding inferomarginals have a few broad, pointed spinelets, as well as granules. The oral intermediates form a triangular area comprised of rows of plates connecting between adambulacrals and inferomarginals up to the 10th or 17th inferomarginal. Each plate is armed with unequal, crowded granules, the central ones flat and lance-shaped, as on inferomarginals. The adambulacrals bear 5 or 6 flat furrow spines, and some shorter, stouter spines continue around the edge of each plate. The oral surface has 1 to 3 more robust, bluntly pointed spines. The adjoining mouth plates share a single large apical spine, and each has about 7 marginal spines.
Pseudarchaster alascensis might be confused with Mediaster aequalis or Gephyreaster swifti. Compare the descriptions and illustrations of the marginal plates in these species.
The stomachs of Pseudarchaster alascensis specimens contained gastropods, brittle stars, small crustaceans, foraminiferans and sediment. This sea star appears to reach full size in four years. Its breeding season is not known.
Sea of Japan, Sea of Okhotsk, and Bering Sea to Oregon in depths of 92 to 1947 metres. Common on mud, sand, gravel and rock, but most often on soft substrates. Pseudarchaster parelii (Düben and Koren, 1846) is considered circumboreal at depths of 15 to 2,500 metres, but Halpern (1972) proposed that the subspecies P. parelii alascensis Fisher, 1911, be raised to species status.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2020-02-17 3:56:03 AM]
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