Özet:

In this study, we investigated the morphological characteristics and phylogenetic position based on the 18S rDNA gene sequence of the Spathidium species isolated from the coastal sands of Lake Van. Three populations of ciliates were observed, showing different morphology in cultures. Our results indicate that the nucleotide sequences of the 18S rDNA gene region of these populations were similar and they were different developmental stages of the same species. Phylogenetic analyses based on the nucleotide sequences of the 18S rDNA gene region showed that Spathidium sp. isolated in this study clustered together with Lagnophrya acuminata, Enchelys gasterosterus, and Balantidion pellucidum rather than their congeners. There are contradictions between the morphological classification system and molecular phylogeny of Spathidiid ciliates, and it is seen that the genus Spathidium is a paraphyletic taxon. However, the lack of nucleotide sequence data for many species of the species-rich genus Spathidium limits the elucidation of the molecular phylogenetic status of this taxon. Phylogenetic analyzes using different gene regions with the support of detailed morphological data to be isolated from different habitats will clarify this problem.