The rotifers found in the plankton samples of Lake Biwa-ko

Lake Biwa-ko is well known by the occurrence of a large number of endemic species among the various groups of animals, while, so far as the rotifer fauna is concerned, the special faunal characters are not observed. The numbers of rotifer species which are extraordinarily ubiquitous, are not so large in this lake, but the unusual species are seldom seen as well. Most of the rotifers recorded belong to the vulgar ones. Some of the rotifers found in the plankton samples are often to be the dominants or subdominants of the zooplankton, when the individual numbers are taken up.As Lake Biwa-ko is situated near the centre of our country, both the boreal and the austral rotifers are collected there. The plankton rotifers of Lake Biwa-ko is said to be represented by the typical members in the oligo- or mesotrophic lakes of the temperate region.