Most of these reproductive modes include equal fission or budding. In Blebbistatin certain ciliates, including Tetrahymena patula and Colpoda inflata, reproduction can also occur inside the cyst wall, viz. reproductive cysts [3, 4]. Symbiotic ciliates

like the astome ciliates, e.g., Radiophrya spp., and certain apostome ciliates, e.g., Polyspira ABT-888 order spp., reproduce by forming cell chains, also called catenoid colonies, which are usually brought about by repeated asymmetric division without separation of the resulting filial products [3, 5]. Some Tetrahymena, such as temperature-sensitive cytokinesis-arrested mutants of T. thermophila- strain cdaC, and T. pyriformis also showed similar cell chains at high temperature [6, 7] and similar morphotypes were also recently reported in the non-reproductive artificial lethal mutants of T. thermophila [8]. However, no free-living ciliates have been reported to form cell chains in response to food (bacteria) concentration. During early and late phases of equal fission, most ciliates share certain THZ1 clinical trial features, such as common positioning of the macronucleus

and the micronucleus, synchronization of macronuclear amitosis and fission furrow, and a specific and well defined dividing size [9–11]. It is generally assumed that if food density meets requirements of both cell development and division, the daughter cells will be identical, so after division, the two daughter cells could not be differentiated from each other [12–14]. However, ciliates from the same single cell isolate were reported to have high diversity in physiological states, such as cell size and volume, growth rate, feeding and digestion [15–18], and certain ciliates even develop highly unique physiological strategies to maximally adapt to their habitats. For example, after feeding on the cryptomonad Geminigera cryophila, the mixotrophic red-tide-causing ciliate Myrionecta rubra retains the prey organelles, which continue to function in the ciliate for up to 30 days [19, 20]. Comprehensive analysis of physiological state changes of ciliates usually requires monitoring of individuals for a relatively long period and

therefore is rarely conducted [15]. Most ciliates Endonuclease are currently unculturable or swim too fast for microscopic observation, further hindering such analyses. In this study, we describe a series of reproductive strategies that have been previously unknown in free-living ciliates. These types of reproduction occurred in all newly established cultures of G. trihymene, a free-living scuticociliate belonging to the class Oligohymenophorea, which also includes Tetrahymena and Paramecium. The division processes and the relationship between persistence time of asymmetric divisions and bacteria concentrations are described, and an updated life cycle and phylogenetic position of G. trihymene are presented. Results Natural History of G. trihymene The G. trihymene isolate described here, collected in Hong Kong, is free-living and bacterivorous.