Discomorphella pedroeneasi sp. nov. (Ciliophora, Odontostomatida): An anaerobic ciliate hosting multiple cytoplasmic and macronuclear endocytobionts.

Odontostomatids are among the less studied representatives of the Ciliophora. They are anaerobic microeukaryotes usually occurring as rare species in sapropelic environments. Here we describe a novel species of Discomorphella, named Discomorphella pedroeneasi sp. nov., using light and electron microscopy observations. Discomorphella pedroeneasi displays many complex morphological features, for which new terms are introduced, such as the auricules, epistomial fringe spacer, frontal awning, odontostomatid ciliary sockets, oral lips and ventral flap. Remarkably, D. pedroeneasi has at least six types of endocytobionts, including intramacronuclear ones, and organelles ultrastructurally similar to the M/H bodies of the odontostomatid Saprodinium dentatum. Based on the new data and revision of the literature, we propose two new diagnostic characters for species separation within Discomorphella: the fringe spacer ratio and the posterior fringe ratio. The taxonomy of Discomorphella is revised and an identification key is provided.