Two New Genera of Planktonic Ciliates and Insights into the Evolution of the Family Strombidiidae (Protista, Ciliophora, Oligotrichia)

PLoS One. 2015 Jun 29;10(6):e0131726. doi: 10.1371/journal.pone.0131726. eCollection 2015.


Oligotrich ciliates are common marine microplankters, but their biodiversity and evolutionary relationships have not been well-documented. Morphological descriptions and small subunit rRNA gene sequences of two new species representing two new strombidiid genera, Sinistrostrombidium cupiformum gen. nov., sp. nov. and Antestrombidium agathae gen. nov., sp. nov. are presented, and their taxonomy and molecular phylogeny are analyzed. Sinistrostrombidium gen. nov. is characterized by a sinistrally spiraled girdle kinety and a longitudinal ventral kinety. Antestrombidium gen. nov. is distinguished by tripartite somatic kineties (circular and ventral kineties plus dextrally spiraled girdle kinety). Sinistrostrombidium and Antestrombidium branched separately from one another in phylogenetic trees, clustering with different clades of strombidiids. The new genera added to the diversities of ciliary patterns and small subunit rRNA gene sequences in strombidiids leads to presentation of a new hypothesis about evolution of the 12 known strombidiid genera, based on ciliary pattern and partly supported by molecular evidence. In addition, our new morphological and molecular analyses support establishment of a new order Lynnellida ord. nov., characterized by an open adoral zone of membranelles without differentiation of anterior and ventral membranelles, for Lynnella, but we remain unable to assign the genus to a subclass with confidence.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Evolution*
  • China
  • Ciliophora / classification*
  • Ciliophora / genetics
  • Genes, rRNA
  • Phylogeny
  • Plankton / classification*
  • Plankton / genetics

Grant support

Financial support was provided by the National Natural Science Foundation of China (projects numbers: 31222050, 31172060, 31201696, 31430077, 31471973), Research Fund for the Outstanding Young Teachers Program of Higher Education in Guangdong (Yq2013052), and the International Research Coordination Network for Biodiversity of Ciliates funded jointly by the U.S. National Science Foundation (oDEB) and the National Natural Science Foundation of China (project number: 31111120437).; The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.