Traditionally the phylum Rotifera was divided into three groups: Seisonidea (marine), Bdelloidea (ca. 370 species) and Monogononta (ca. 1450 species), however more recently only two classes have been suggested: Pararotatoria (Order Seisonacea) and Eurotatoria (Subclasses Bdelloidea and Monogononta).

• The Bdelloidea females are characterized by paired ovaries, a ramate trophi and the absence of a hard lorica. Bdelloids inhabit a variety of environments (mostly springs, streams, rivers, mosses and peat bogs), and have a strict parthenogenetic reproduction. This group is also capable of long desiccation periods or anabiosis.
• The Monogononta are characterised by a single gonad, a species-specific trophi, and might have a loricate body1. They have a cyclic parthenogenetic reproduction. Their morphology can vary widely according to the type of habitat. Monogononts are generally very abundant in lakes, ponds and wetlands but are also numerous in species number and densities in riverbed sediments and sand beaches.
• The Seisonacea are marine epizoic rotifers that have female and male individuals. They have paired gonads, a fulcrate trophi and functional gut in females and males. This group has only 4 known species.

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Rotifer Bauplan
Rotifer feeding
Rotifer reproduction

1. Koste, W. 1975. Mikrokosmos 11: 341.