trihymene sequence [GenBank Accession No.: AY169274]. Figure 4 Phylogenetic position of G. trihymene. Maximum likelihood tree topology and branch lengths, rooted with species marked with **. Support for clades is indicated by ML boostrap/MP bootstrap/MB posterior probabilities. N indicates that this clade was not found in the given analysis and asterisks indicate clades with support of less than 50%.

Nodes with <50% support in all methods are shown as a polytomy. Scale bar: 5 substitutions per 100 nucleotide positions. Discussion Updated life cycle of G. trihymene during vegetative RGFP966 growth The life cycle during vegetative growth of G. trihymene is generalized in Figure 5, based on previous and current studies [21, 22]. The life cycle has multiple stages, as is typical in polyphenic ciliates. These life stages could be highly diverse and complex, depending on the total number of asymmetric divider morphotypes and food concentration. For simplification and clarity, most intermediate asymmetric dividers are not shown in Figure 5. Figure 5 Updated life cycle of G. trihymene in vegetative Vactosertib solubility dmso growth. This is generalized from continuous microscopy

and observation of specimens after protargol impregnation. Note the first asymmetric dividers (probably more than three morphotypes) with different sizes and shapes in early PLX-4720 cultures developed Liothyronine Sodium through the arrest of cytokinesis in some trophonts. Drawings are not strictly to scale. Information on micronuclei is not available. Some free-living ciliates, for example, Tetrahymena pyriformis, produce maximal progeny cells by shifting their physiological states during starvation [23]. Similarly, G. trihymene produces progeny cells by combining three reproductive modes: asymmetric division, reproductive cysts and equal fission. In addition, this is the first report of reproductive

cysts in scuticociliates, though they are not uncommonly found in certain ciliate genera, like Colpoda and Tetrahymena [4]. If each morphotype of asymmetric dividers could be deemed as one life stage, which could probably be the case as many similar or continuous asymmetric divider morphotypes were repeatedly found in cultures with different “”age”" or media, then the updated life cycle of G. trihymene might rival most known life cycles of free-living ciliates in complexity (Figure 5). G. trihymene thus provides a special opportunity for studying ciliate polyphenism. Although G. trihymene was first discovered early in 1966, it was believed to reproduce only by equal fission during vegetative growth [21, 22]. One reason for the persistence of this narrow view of G. trihymene reproduction is that, to date, few studies have been conducted on G. trihymene and they have mainly focused on morphology or systematics rather than reproduction dynamics [21, 22].