Biogeography of Isopod Crustaceans in the Boreal Pacific

Publisher： University of Miami - Rosenstiel School of Marine and Atmospheric Science

ISSN： 0007-4977

Source： Bulletin of Marine Science, Vol.46, Iss.3, 1990-05, pp. : 620-639

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Abstract

The isopod fauna of the Pacific Boreal Region (the Steller region), defined as the area north of a line between Cape Inubo and Cape Conception, includes 409 species. Research on their vertical distribution shows two faunas in the northern Pacific that are distinctly different in composition of genera, and even families: the shallow-water, primarily shelf fauna, and the deep-sea fauna (abyssal-ultra abyssal). The shelf shallow-water fauna dominates to 1,500 m depths, and the deep-sea fauna is found below 2,000 m. A third bathyal fauna, occurring between (200–2,000 m), is poor and has mixed characteristics, but is mostly similar to the shelf fauna, with which it has been included. The shelf fauna is dominated by Idoteidae and Arcturidae, and by the lower janiroidean Asellota, mainly Janiridae and Munnidae. The deep-sea fauna contains mostly the higher janiroidean Asellota, with a secondary component consisting of immigrants of distinctly Antarctic origin (Antarcturus). An analysis of recent isopod distributions provides no indication that the Pacific Boreal Region is a center of formation for the deep-sea fauna. The isopod fauna of the shelf zone shows very little similarity on the species level to the faunas of the adjacent Arctic and boreal Atlantic oceans. The Pacific Boreal or Steller region is divided into the high-boreal Beringian subregion, and the low-boreal Manchurian and Oregonian subregions. Within the Beringian subregion, the following provinces can be distinguished: Lamutian (Okhotsk), Kurile and Aleutian. Within the Steller region, relative antiquity of the subregions and their component provinces can be qualitatively estimated.