Phylogenetic consideration of two scuticociliate genera, Philasterides and Boveria (Protozoa, Ciliophora) based on 18 S rRNA gene sequences

Many scuticociliates are facultative parasites of aquatic organisms and are among the most problematic ciliate taxa regarding their systematic relationships The main reason is that most species especially taxa in the order Thigmotrichida have similar morphology and have not been studied yet using molecular methods In the present work two scuticociliate genera represented by two rare parasitic species Philasterides armatalis (order Philasterida) and Boveria subcylindrica (order Thigmotrichida) were studied and phylogenetic trees concerning these two genera were constructed based on their 18 S rRNA gene sequences The results indicate that 1) Philasterides forms a sister group with Philaster supporting the classification that these two genera belong to the family Philasteridae 2) it is confirmed that the nominal species Philasterides dicentrarchi Dragesco et al 1995 should be a Junior synonym of Miamiensis avidus as revealed by both previous investigations and the data revealed in the present work and 3) the poorly known form B subcylindrica the only member in the order Thigmotrichida of which molecular data are available so far always clusters with Cyclidium glaucoma a highly specialized scuticociliate indicating a sister relationship between the orders Thigmotrichida and Pleuronematida (C) 2010 Elsevier Ireland Ltd All rights reserved