Hypotrichia, one of the most complex and highly differentiated groups in Ciliophora, has been the object of extensive studies, especially in recent years. Nevertheless, methodological difficulties and insufficient faunistic studies have limited our understanding of their biodiversity and phylogeny. In this study, one novel urostylid ciliate, Pseudoholosticha zhaoi nov. gen., nov. spec. and two populations of Anteholosticha monilata (Kahl, 1928) Berger, 2003, type species of the latter genus, are studied using an integrative approach (live observation, protargol impregnation, scanning electron microscopy, and phylogenetic analysis) to provide further insights into the diversity, classification, and phylogeny of this group of ciliates. Pseudoholosticha nov. gen. can be separated from other morphologically similar genera mainly by the absence of buccal and caudal cirri. A key to 12 morphologically similar genera and illustrations of their cirral patterns are provided. The validation of the new genus and new species is supported by both morphological and phylogenetic analyses. The first 18S rRNA gene sequence of A. monilata, with detailed morphological data, provided a reliable clarification of A. monilata populations and corroborated the phylogenetic position of the type species of the polyphyletic genus Anteholosticha.

Department of Zoology Faculty of Science Charles University Prague 128 43 Czech Republic

Institute of Evolution and Marine Biodiversity Ocean University of China Qingdao 266003 China

Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences Institute of Hydrobiology Chinese Academy of Sciences Wuhan 430072 China

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Hypotrichidium tisiae (Gelei, 1929) Gelei, 1954: a unique hypotrichid ciliate having a highly specialized developmental pattern during binary division