Latitudinal range of epiplanktonic chaetognatha and ostracoda in the western tropical Indian Ocean

An account of the chaetognath and ostracod species obtained from zooplankton samples collected along a transect in the Western Indian Ocean between 9° N–20° S and 57° 18–68° 43E in January–February 1981 is given. Species richness was maximum north of 10° S. The latitudinal variation of thirteen species of chaetognaths indicated that many of the typical Indo-Pacific species are restricted to the tropical zone with limited penetration into the subtropical region. All the sixteen species of planktonic ostracods were cosmopolitan. Based on the available information on the distribution of chaetognaths and ostracods, the species assemblages in the Indian Ocean are discussed.