Taxonomy and molecular phylogeny of four Strombidium species, including description of S. pseudostylifer sp. nov. (Ciliophora, Oligotrichia)

Oligotrich ciliates are important components of marine microplankton and have a high biodiversity. In the present paper, the morphology and small subunit rRNA (SSrRNA) gene sequence of four Strombidium species are recorded, including a new species, S. pseudostylifer sp. nov. that was sampled from a mangrove wetland. This new species is characterized by its prominent apical protrusion, long constant tail and large number of ventral dikinetids. In addition, the morphology of two poorly known species, S. chlorophilum Montagnes et al., 1988 and S. oculatum Gruber, 1884 are redescribed based on the Chinese populations and their diagnoses are improved. The morphology of three populations of S. stylifer Levander, 1894 collected from three sampling sites in China are also compared, revealing that the only difference between them are the sizes of their cells and macronuclei. Finally, the phylogenetic analyses of the above four Strombidium species, as inferred from their SSrRNA gene sequence data, show that S. oculatum, S. stylifer and S. pseudostylifer cluster within the main Strombidium branch while S. chlorophilum clusters with S. conicum and branches from the main Strombidium group.http://zoobank.org/urn:lsid:zoobank.org:pub:E869E485-8F29-4B2B-8BB2-D3A039AA6403