Molecular evolution in hypotrichous ciliates: Sequence of the small subunit ribosomal RNA genes fromOnychodromus quadricornutus andOxytricha granulifera (Oxytrichidae,Hypotrichida, Ciliophora)

Summary The small subunit ribosomal RNA (16S-like rRNA) coding regions of the hypotrichous ciliatesOnychodromus quadricornutus andOxytricha granulifera were amplified using polymerase chain reaction techniques. Complete sequences were determined for the amplified genes and compared to those of other ciliated protozoa. In phylogenetic trees inferred using distance matrix methods oxytrichids are not seen as a cohesive phylogenetic group.Oxytricha nova is most closely related toStylonychia pustulata in a lineage that also includesO. quadricornutus. This phylogeny contradicts phylogenetic schemes in whichOnychodromus is considered to be a primitive hypotrichous ciliate and suggests thatO. nova was misidentified as members of the genusOxytricha.