Morphology, ontogeny and molecular phylogeny of a new urostylid ciliate, Bakuella (Pseudobakuella) guangdongica n. sp. (Ciliophora, Hypotrichia) from southern China.

The morphology, morphogenesis, and molecular phylogeny of Bakuella (Pseudobakuella) guangdongica n. sp., isolated from southern China, were investigated. The new species is characterized by a body length of 150-225 μm in vivo; 35-42 adoral membranelles; 3-5 buccal, two frontoterminal, 7-12 transverse and two pretransverse ventral cirri; midventral complex comprised of 10-20 pairs and two rows extending to transverse cirri; posterior part of marginal rows slightly overlapping; colorless cortical granules about 1 μm across, arranged in small groups; soil habitat. Its main ontogenetic features are: (1) in the proter, the parental adoral zone of membranelles is completely renewed by new structures; (2) in the opisthe, the oral primordium originates apokinetally, some old midventral cirri join the formation of frontoventral-transverse cirral anlagen; (3) the anlagen for marginal rows and dorsal kineties develop intrakinetally; and (4) the numerous macronuclear nodules fuse into a single mass before dividing. Phylogenetic analyses based on the SSU rDNA sequence suggest the non-monophyly of the genus Bakuella.