Phylogeny, morphology, and ultrastructure of sessilid peritrich ciliates in termite guts, Termitophrya africana and Doliophrys denislynni gen. nov., sp. nov.

Sessilids (Oligohymenophorea, Peritrichia, Sessilida) reportedly colonize the gut of certain "higher termites" (family Termitidae), but only a single species, Termitophrya africana from Jugositermes tuberculatus (subfamily Apicotermitinae), has been described based on a drawing. Similar ciliates were observed in other Apicotermitinae but remained unspecified. Our SSU rRNA gene-based survey of peritrich ciliates in a broad range of Termitidae recovered distinct phylotypes from several Apicotermitinae (Astalotermes, Jugositermes, and Phoxotermes), albeit only from samples collected in Cameroon and not from all species of these genera. They form a monophyletic group in the family Epistylididae (Sessilida), with Orborhabdostyla bromelicola as the closest relative. Light, scanning, and transmission electron microscopy of the sessilid ciliates in J. tuberculatus revealed two morphotypes, which were assigned to their corresponding phylotypes by sequence analysis of capillary-picked single cells. One morphotype, which is highly contractile and broadens continuously towards the posterior end, matches the description of Termitophrya africana. The cells are attached by a posterior scopula with short cilia and are often covered with rod-shaped ectobionts. The other morphotype has a stockier, barrel-shaped body and a short, clearly demarcated anterior end and is always free of ectobionts. We designate it as Doliophrys denislynni gen. nov., sp. nov.