Taxonomy, molecular phylogeny and macroevolutionary aspects of sessilid ciliates (Peritrichia: Sessilida), with emphasis on the Epistylididae family

Abstract

Sessilida (Ciliophora, Peritrichia), one of the most diverse and widely distributed orders within the ciliated microeukaryotes, is composed of about 600 species divided into 14 families and over 100 genera. Members of this order exhibit different ways of life and can be found all over the world, in different environments. Sessilids have been investigated since the beginning of studies with ciliated microeukaryotes, but many doubts still exist regarding their morphology, ecology and evolution. Aiming to generate more information to try to solve the doubts that exist for the sesilid individuals, mainly the representatives of the Epistylididae family, we carried out an extensive review on two genera of this family, Apiosoma and Rhabdostyla, and also investigated the existence of a phylogenetic signal for the type of environment. and the influence of this ecological feature on evolution and diversity for the entire Peritrichia class using the 18S-rDNA marker. As a result of the reviews, we systematically and comparatively compiled morphological information for 62 species of the genus Apiosoma and 45 species of the genus Rhabdostyla, and other related genera. In addition, we found a phylogenetic signal for the environment within Sessilida and, through an ancestral state reconstruction analysis, we found results that suggest that individuals of this subclass originated in freshwater environments and only more recently colonized the other environments where they are currently located.