Phylogeny of a new ciliate family Clampidae fam. nov. (Protista: Ciliophora), with notes on morphology and morphogenesis

Hypotrichs comprise a highly differentiated and diversified group of ciliates with an evolutionary history characterized by an exceptional number of convergences and reversions. A new hypotrich ciliate from a freshwater fishpond is investigated based on morphological, morphogenetic and molecular data. The phylogenetic analyses reveal that the new species is closely related to Simplicitergida despite the absence of zigzag-patterned midventral cirral pairs, a common feature of simplicitergids. The phylogenetic position of this atypical simplicitergid species is strongly supported by the conserved features of dorsal ciliature and nuclear apparatus, which are probably more informative than cirral patterns for higher-rank classification. The close phylogenetic relationships among those Simplicitergida with varied cirral patterns could be explained by evolutionary convergences and reversions. The new species is recognized mainly by three frontoventral rows, several short midventral rows, two long midventral rows and the absence of zigzag-patterned midventral cirral pairs. Based on comprehensive phylogenetic analyses, together with detailed morphological and morphogenetic comparisons, a new family, Clampidae fam. nov., is proposed for the new genus and species, Clampia sinica gen. et sp. nov. In addition, an emended diagnosis of the morphologically similar family Epiclintidae is provided.