New Morphologic Features for Explaining Molecular Phylogenies in Oligotrichea, an Ecologically Important Group of Planktonic Protists (Alveolata, Ciliophora, Spirotricha)

Oligotrichea are an ecologically important group of mainly marine planktonic ciliates (Alveolata, Ciliophora, Spirotricha). They comprise about 200 aloricate (naked) species and about one thousand loricate (house-forming) tintinnids. The relationships among the Oligotrichea are poorly understood, especially those among the tintinnids, whose identification and classification are exclusively based on variable lorica features. Since the molecular phylogenies reveal surprising relationships and non-monophylies, morphological studies of new and insufficiently known species and subsequent cladistic analyses have thus (i) to provide apomorphic features to be mapped on the gene trees and (ii) to reassess the known characters. The present proposal suggests an extraordinary integrative approach by combining commonly used taxonomic and genetic methods with transmission electron microscopy. The investigations are based on culture and field material of marine and freshwater Oligotrichea. The cultures are provided by Austrian, Swiss, and Italian colleagues, while the field material is sampled by us in the Mediterranean Sea, the North Sea, and Austrian lakes. By combining live observation, protargol staining, and scanning electron microscopy, new species are described and insufficiently known species are redescribed. The application of transmission electron microscopy provides deeper insights into the cells, revealing new taxonomically and phylogenetically relevant characters. Parallel to gene sequence analyses performed in cooperation with colleagues from Germany and the USA, cladistic analyses of the morphological and ultrastructural features of the cells, loricae, and further life cycle stages enable the establishment of hypotheses about genealogies. The discovered morphologic synapomorphies can finally be mapped on the gene trees, explaining the previously surprising relationships. The main objectives are (i) to describe new species and to redescribe insufficiently known species, mainly tintinnids, at highest scientific level, (ii) to extend the taxonomic scope by providing novel morphologic features, especially of the ultrastructure in representative species, and (iii) to address questions of relationships among the Oligotrichea. Specifically, the ultrastructural adaptations related to the transitions to freshwater and the switch to the ecologically important mixotrophic nutrition mode are for the first time in the focus of investigations. Cladistic analyses of the new characters will reduce/delete the divergences from the molecular phylogenies and enable a revision of the classification.