The morphology and phylogeny of two euplotid ciliates, Diophrys blakeneyensis spec. nov. and Diophrys oligothrix Borror, 1965 (Protozoa, Ciliophora, Euplotida)

Abstract

The morphology, infraciliature and molecular phylogeny of two marine ciliated protozoans, Diophrys blakeneyensis spec. nov. and Diophrys oligothrix Borror, 1965, isolated from British salt marshes, were investigated using microscopic observations of live and protargol-impregnated specimens, and by small subunit (SSU) rRNA gene sequence analysis. Diophrys blakeneyensis spec. nov. is characterized as follows: cell oval to rectangular in outline; size variable, approximately 60–180 × 30–80 µm in vivo; adoral zone comprising about 45 membranelles; usually five frontal, two ventral, five transverse, two left marginal and three caudal cirri; five dorsal kineties with more than 10 dikinetids each; 7–23 spherical to ellipsoid macronuclear nodules in a ring-like pattern; marine biotope. The population of Diophrys oligothrix described here corresponds well with previous populations in terms of its general morphology and ciliary pattern, in particular the continuous ciliary rows on the dorsal side with loosely arranged cilia. The main differences between the present and previously reported populations are the broader buccal field and greater number of dorsal kineties in the present population, both of which are regarded as population-dependent features. Phylogenetic analyses based on SSU rRNA gene sequence data demonstrate that Diophrys blakeneyensis is most closely related to Diophrys oligothrix, and both organisms cluster with two congeners with high bootstrap support within a larger group that contain the core species of the Diophrys-complex. Cladistic analysis based on morphological and morphogenetic data broadly agree with the SSU rRNA gene sequence phylogeny. Both analyses suggest that the genus Diophrys may be polyphyletic.