Replication of basal bodies during ciliogenesis in the epidermis of Prolecithophora and Lecithoepitheliata (Plathelminthes)

Centriologenesis has been little studied in the Plathelminthes. Taking into account the importance of ultrastructural features for phylogenetic reconstructions, we studied the development of cilia in mature turbellarians Friedmaniella sp. (Prolecithophora), Geocentrophora wagini, and Geocentrophora intersticialis ( Lecithoepitheliata) to compare the events of centriolo- and ciliogenesis in their epidermis. In all these species the formation of the multitude of centrioles follows the acentriolar pathway. In Friedmaniella sp., each centriole appears inside an individual filamentous accumulation. In G. wagini, the procentrioles arise in clusters of fibrous granules. Several procentrioles are usually produced in a separate cluster. Such a very big cluster of fibrous granules was also found in one cyton of G. intersticialis. The assemblage of cilia starts on the basal bodies with rootlets either in the cytoplasm of the epidermal layer or on the cell surface, after these basal bodies dock with the apical cell membrane. The last developmental mode is the only one found in epidermis of G. intersticialis. Both our results and the literature data suggest that the knowledge of ciliogenesis could assist in reconstructing phylogenetic trees of Plathelminthes.