Morphology and phylogeny of two anaerobic freshwater ciliates: Brachonella comma sp. nov. and the widely distributed but little‐known caenomorphid, Ludio parvulus Penard, 1922

Abstract

Hypoxic, sulfidic freshwater sediments typically support a diffuse consortium of distinctive ciliated protists, including caenomorphids, metopids, and odontostomatids among others. A recent resurgence of interest in these important members of sapropelic food webs has resulted in the description of many new species and an effort, still in its infancy, to characterize them from a morphologic, molecular, and metabolic standpoint and to determine their phylogenetic relationships. Their seemingly invariable association with prokaryotic endosymbionts and, less commonly, ectosymbionts has become a focus for many researchers. In this report, based on morphologic and molecular data, we describe a Brachonella species (Ciliophora, Metopida) new to science and analyze its phylogeny. We also provide a morphologic and molecular characterization of the smallest representative of the Caenomorphidae Poche, 1913, Ludio parvulus Penard, 1922. The phylogenetic analysis confirms the inclusion of this species in the Caenomorphidae.

Morphology and phylogenetic position of three anaerobic ciliates from the classes Odontostomatea and Muranotrichea (Ciliophora)

“…The overall phylogenetic tree topology differs slightly from that of previous analyses (Bourland et al, 2022;Campello-Nunes et al, 2022;Zhuang et al, 2022). Interestingly, the clade of Caenomorphidae resulted sister of Muranotrichea in our phylogenetic analyses, throughout low support, rather than to Litostomatea as in previous analyses (Li et al, 2017;Rotterová et al, 2020).…”

“…In previous 18S rRNA analyses, the class Odontostomatea was sister to Armophorea (Metopida + Clevelandellida), branching within the APM clade (Bourland et al, 2022; Fernandes et al, 2018; Rotterová et al, 2020; Zhuang et al, 2022). In the present phylogenetic trees, as well as in others (Campello‐Nunes et al, 2022), the class Odontostomatea is sister to Litostomatea.…”

“…Anaerobic ciliates have received increased attention during the last decade. Most of the published studies deal with their taxonomy, diversity, and phylogenetic position using standard methods, for example, protargol impregnation, scanning electron microscopy, and single‐gene phylogenies (Bourland et al, 2014, 2017a, 2017b, 2020, 2022; Bourland, Rotterová, & Čepička, 2018; Bourland, Rotterová, Luo, & Čepička, 2018; Bourland & Wendell, 2014; Campello‐Nunes et al, 2020, 2022; da Silva‐Neto et al, 2016; Fernandes et al, 2018; Foissner, 2016a, 2016b; Li et al, 2017; Li, Zhuang, Pérez‐Uz, et al, 2021; Li, Zhuang, Wang, et al, 2021; Méndez‐Sánchez et al, 2022; Nitla et al, 2019; Orsi et al, 2012; Paiva et al, 2017; Poláková et al, 2021; Rotterová et al, 2018; Vďačný et al, 2019; Vďačný & Foissner, 2017a, 2017b, 2019; Zhuang et al, 2021, 2022). Other studies have provided insights into features of their anaerobic lifestyle, for example, evolution, metabolism, and symbioses with various prokaryotes (Beinart et al, 2018; Lewis et al, 2018; Muñoz‐Gómez et al, 2021; Newbold et al, 2015; Omar et al, 2017; Rotterová et al, 2022).…”