Phylum Rotifera:
Class Digononta :
Rotifers in this class have paired ovaries. There are two orders: Bdelloidea and Seisonidea. The Seisonidea consists of two species in one genus Seison. These rotifers are epizoic on the gills of a leptostracan crustacean, Nebalia. The corona is very reduced and is not used in food gathering or locomotion. These rotifers are not included in the following key. Order Bdelloidea is described below.
Class Monogononta :
Class Monogononta comprises the largest group of rotifers with more than 1600 species in about 95 genera of benthic, free-swimming, and sessile forms. Key characteristics include females possessing one ovary with a vitellarium, and trophi other than ramate. Males are structurally reduced, and are present only for a few days or weeks each year.
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