There are over 2000 of rotifers and virtually every genus

There are over 2000 of rotifers and virtually every genus contains species with strange characteristics. Most are females and very few are males. These wheel animalcules dates back nearly three centuries to their first description in 1703 by Leeuwenhoek. Some examples are: Euchlanis Asplanchna (found in the Great Lakes) and Conochilus (found in clean lakes and pounds and in colonies). Nicely organized nice pictures are on this site: http://www.ucmp.berkeley.edu/phyla/rotifera/rotifera.html