On the evolution and morphology of the rotiferan trophi, with a cladistic analysis of Rotifera

The phylogeny of Rotifera was examined in different computer-generated cladistic analyses, including Seisonidea, Bdelloidea, Flosculariacea, Collothecacea and all ploimids treated on family level. The analyses were based on a character matrix solely dealing with morphological characters, primarily based on the trophi morphology. Limnognathia maerski (Micrognathozoa), Rastrognathia macrostoma and Gnathostomula paradoxa (Gnathostomulida) were used as outgroups. The cladistic analysis performed by paup produced 288 most parsimonious trees. peewee analyses produced between 140 and 432 trees, depending on the concavity value. The monophyly of Eurotatoria, Monogononta and Ploima was confirmed in all obtained trees. All analyses suggested a division of Ploima into major clades. One clade corresponded to Transversiramida while the other contained all other ploimid taxa and recognized Antrorsiramida as a monophylum. Based on the obtained results a scenario for the trophi evolution is proposed. The analyses suggested that the presence of an incus is synapomorphic for Gnathifera while mallei are synapomorphic for Micrognathozoa and Rotifera. The ancestral rotifer trophi probably resembled those in Harringia (Asplanchnidae).