Morphological, ontogenetic, and phylogenetic research of a poorly known non-dorsomarginalian ciliate: Erniella filiformis Foissner, 1987 (Protista, Ciliophora, Hypotrichia).

Erniella Foissner, 1987 is a poorly known genus with its available information limited solely to morphological characteristics. In this study, the type species E. filiformis, isolated from highly saline water in China, was investigated for morphology, morphogenesis, and phylogeny based on small subunit ribosomal DNA sequences. The main characteristic events during morphogenesis in Erniella filiformis are as follows: (1) in the proter, only the posterior part of the parental adoral zone is renewed and undulating membranes anlage is formed from the dedifferentiation of the old structure; (2) the oral primordium is formed intrakinetally in the opisthe; (3) frontoventral-transverse cirral anlagen II-IV develop in the primary mode, anlage V develops intrakinetally in the proter; and (4) the right frontoventral row is formed by a single anlage. The phylogenetic analyses indicate that Erniella forms a monophyletic group with Bistichella, Keronopsis, Lamtostyla, Orthoamphisiella, Parabistichella, Paraholosticha, and Uroleptoides.