Latitudinal distribution of pelagic ostracods (Myodocopa) in the Australian-New Zealand sector of the South Ocean

Abstract

Data of Russian surveys in the Australian-New Zealand sector of the South Ocean in 1956-1983 are presented. Fauna of ostracods in this region includes 66 species belonged to 35 genera, 4 subfamilies and 2 families that is more than in the Atlantic and Indian sectors of the South Ocean but less than in the Pacific sector. Both total abundance and species composition of ostracods change with latitude, as well as the abundance of mass species, namely the number of species and their abundance decrease from the Subtropical Convergence toward Antarctica but the number of cold-water species and portion of endemic species increase in the same direction, while dominant species are replaced in the order: wide-spread + subantarctic → wide-spread + antarctic → proper antarctic ones. Pelagic ostracods in the Subantarctic zone are mainly allochthonous species with very low portion of endemic ones; this zone is not biogeographically independent but is a transitional area between the Tropical and Antarctic zones. As compared with the Northern Hemisphere, the pelagic ostracods abundance in the Subantarctic and Antarctic zones is higher than in the Boreal and Arctic zones.