Ontogenesis and Molecular Phylogeny of the Marine Ciliate Diophryopsis hystrix: Implications for the Systematics of the Diophrys-like Species (Ciliophora, Spirotrichea, Euplotida)

ABSTRACT. The cortical development of Diophryopsis hystrix , a small marine euplotid ciliate, was observed during binary division. The pattern of morphogenesis is generally similar to that of other Diophrys- like species, with the exception of the marginal cirrus, which develops in a unique manner in D. hystrix being formed from the posterior end of the dorsal kinety anlage, in a similar manner to the formation of the caudal cirri. In the small subunit (SS) rRNA gene sequence tree, Diophryopsis represents a distinct clade separate from Diophrys . Furthermore, our ontogenetic and SSrRNA gene sequence data both support the suggestion that the Diophrys complex is sister to Uronychia , and should be considered as a distinct subfamily within the family Uronychiidae, i.e. Diophryinae Jankowski, 1979, comprising Diophrys , Diophryopsis , and Paradiophrys . Diagnoses of the subfamilies Diophryinae and Uronychiinae are provided.