Integrative data of an unknown ciliate (Alveolata, Ciliophora) propose the establishment of Caudidiodeviata nov. gen.

Abstract

Background As unicellular eukaryotes, ciliates are an indispensable component of ecosystems that play the role of intermediate nutrition link between bacteria or algae and meifauna. Recent faunistic surveys have discovered many new taxa of hypotrich ciliates, indicating their diversity is greater than previously thought. Here we document an undescribed form isolated from an artificial brackish water pond in East China. Examination of its morphology, ontogenesis and molecular phylogeny suggests it represents a new genus. Results The new genus is distinguished from its relatives by having a dorsomarginal kinety, frontoventral and caudal cirri. It also has five frontoventral cirral anlagen, and oral primordium originated apokinetally between right and left cirral field. The diagnostic traits of the new species include three frontal cirri, one buccal cirrus, one or two parabuccal cirri, a row of four to six frontoventral cirri, three left and two right marginal rows, and one bipolar dorsal kinety with one or two caudal cirri at its rear end. Its main morphogenetic features are: (i) the old oral apparatus is completely inherited by the proter except undulating membranes, which are reorganized in situ; (ii) anlagen for marginal rows and the left dorsal kinety develop intrakinetally in both proter and opisthe; (iii) dorsal kinety 2 is generated dorsomarginally; (iv) in the proter, anlagen I and II originate from the parental undulating membranes and the buccal cirrus, respectively, anlage III from anterior parabuccal cirrus, anlage IV from the parental frontoventral cirri; (v) anlagen I–IV of the opisthe are all generated from oral primordium, and (vi) anlage V occur in the innermost parental right marginal row in both dividers. The phylogenetic analysis suggests that the new species is closely related to the newly described Heterodeviata sinica Song et al., 2023, and then form a robust clade with other deviatids, which corroborates the familial assignment of our form. Conclusions The study of the morphology, and ontogenesis of a new brackish-water taxon increases the overall knowledge about the biodiversity of this ciliate group. It also adds to the genetic data available and further confirms the monophyly of family Deviatidae Foissner, 2016.