In this report, dealing with Uronychia transfuga, ultrastructural details of a member of the genus Uronychia are provided for the first time. The most interesting features appear to be: (1) the lack of an alveolar, electrondense material in the cortex.

The 3 most common morphospecies of Uronychia, i.e. U. setigera, U. transfuga and U. binucleata, were examined in vivo and following protargol impregnation. Among these, U. transfuga is morphologically different to the others (large cell size, more macronuclear

The small subunit rRNA (SSrRNA) genes were sequenced for the hypotrichous ciliates Diophrys appendiculataandUronychia transfuga. These two genera branch one after the other above Euploteson phylogenetic trees of ciliates computed by both distance matrix