[The oncomiracidium of Ancyrocephalus paradoxus Creplin, 1839 (Monongenea, Monopisthocotylea), parasite of Sander lucioperca (Teleostei, Percidae)].

The distribution of ciliated cells and the oncomiracidium chaetotaxy in Ancyrocephalus paradoxus Creplin, 1839 (Ancyrocephalidae) parasite of Sander lucioperca (Teleostean, Percidae) are described for the first time as well as the larval ciliated cells in Dactylogyrus extensus (Dactylogyridae) parasite of Cyprinus carpio. Also is given a description of the larval haptorial armature of Ancyrocephalus paradoxus which shows some original features in our region. The ciliated cell pattern and chaetotaxy are compared among Ancyrocephalus paradoxus (Ancyrocephalidae) Ergenstrema mugilis (Ancyrocephalidae) Dactylogyrus extensus (Dactylogyridae) Tetraonchus menenteron (Tetraonchidae) and Euzetrema knopffleri the systematic position of which is still to be defined. As a result it appears that an unitary pattern occurs in the ciliated cell arrangement and chaetotaxy in the larvae of Ancyrocephalus paradoxus, Ergenstrema mugilis and Dactylogyrus extensus. Yet they are easy to distinguish. Tetraonchus monenteron reveals some affinities with these Dactylogyroïdea but further investigations have to be undertaken again while Euzetrema knoepffleri proves to be very different. In the armature of the larval haptor of Ancyrocephalus paradoxus intraspecific variations appear which seem to be of a biogeographic order. Also the same variations are reported in the larvae of Diplectanum aequans.