Morphogenesis of an anaerobic ciliate Heterometopus palaeformis (Kahl, 1927) Foissner, 2016 (Ciliophora, Armophorea) with notes on its morphological and molecular characterization

Morphology, Morphogenesis and Molecular Phylogeny of Two Freshwater Ciliates (Alveolata, Ciliophora), with Description of Pseudosincirra binaria sp. nov. and Redefinition of Pseudosincirra and Perisincirra

Ciliated microeukaryotes are insufficiently investigated despite their ubiquity and ecological significance. The morphology and morphogenesis of a new Stichotrichida species, Pseudosincirra binaria sp. nov., and the known Perisincirra paucicirrata Foissner et al., 2002, are here studied using live observations and protargol staining methods. The new species is characterized by having one buccal, one parabuccal and three frontal cirri, one frontoventral row extending to the posterior half of the cell, three left and two right marginal rows and three dorsal kineties with the left kinety conspicuously bipartite, along with one caudal cirrus at the rear end of each kinety. During morphogenesis, there exist five frontal-ventral cirral anlagen with anlagen IV and V forming a frontoventral row in the proter, and four cirral anlagen with only anlage IV generating a frontoventral row in the opisthe. The anlagen for marginal rows and dorsal kineties develop intrakinetally. The new population of Perisincirra paucicirrata corresponds well with other isolates regarding morphology and cell development. Phylogenetic analyses based on small subunit ribosomal gene sequence data revealed that both Perisincirra and Pseudosincirra are deeply clustered in the clade consisting of species from the genera Deviata and Heterodeviata, supporting the placement of both genera into the family Deviatidae Foissner, 2016.

Morphology and molecular phylogeny of Pelagothrix abietum (Penard, 1922) comb. nov. and two new Metacystis and Apolagynus species (Ciliophora, Prostomatea)

Ciliates of the class Prostomatea show a broad spectrum of feeding strategies and often occur abundantly in various aquatic habitats, playing a vital role in the biogeochemical cycle. Due to their small cell size and simple structure, prostomateans were considered to be a group with a lower degree of morphological differentiation for a long time. However, recent research suggests that the diversity of this group of ciliates is higher than previously thought. In the present study, three prostomateans, collected from different localities in China and classified into three families, were examined using morphological and phylogenetic techniques. Our analyses revealed two new species, Metacystis multitricha sp. nov. and Apolagynus spiralis sp. nov., and suggested a transfer of Prorodon abietum Penard, 1922 to the genus Pelagothrix. Phylogenetic analyses corroborated the morphological classifications of the three species into the families Metacystidae, Lagynusidae, and Holophryidae, respectively, demonstrating that their diagnostic characteristics bear an evolutionary signal at the family level.

Bit by bit toward the diversity of metopids: Description of the genus Pidimetopus n. gen. (Ciliophora: Armophorea)

While metopids (Armophorea: Metopida) represent the most species-rich group of free-living anaerobic ciliates thriving in hypoxic environments, our understanding of their true diversity remains incomplete. Most metopid species are still characterized only morphologically. Particularly, the so-called IAC clade (named in the past after some of the taxa included, Idiometopus, Atopospira, and Clevelandellida), comprising free-living members as well as the endosymbiotic ones (order Clevelandellida), is in serious need of revision. In our study, we establish a new free-living genus in the IAC clade, Pidimetopus n. gen., with descriptions of two new species, P. nanus n. sp., and P. permonicus n. sp., using up-to-date molecular and morphologic methods. The genus is characterized by small cells (up to 75 μm long), not more than 10 adoral membranelles and eight somatic kineties, and usually, four long caudal cilia that can stiffen. In addition to morphologic and molecular characterizations, we also conducted a statistical morphotype analysis of the polymorphic species P. nanus n. sp. We discuss the relevance of the earlier morphologically described species Metopus minor as a putative collective taxon for several small metopids less than 50 μm long.

Morphology and molecular phylogeny of three Parasonderia species including a new species (Ciliophora, Plagiopylea)

Ciliates of the class Plagiopylea play a vital role in various anaerobic environments as consumers of prokaryotes. Yet, the diversity and phylogeny of this group of ciliates, especially marine representatives, remain poorly known. In this study, three Parasonderia species, viz., Parasonderia elongata spec. nov., and the already known P. cyclostoma and P. vestita, discovered in anaerobic sediments from various intertidal zones in China, were investigated based on their living morphology, infraciliature, and small subunit ribosomal rRNA gene sequences. Parasonderia elongata can be recognized by its larger body size, elongated body shape, oval oral opening, number of oral kineties, and significantly shortened leftmost postbuccal polykineties on the cell surface. Improved diagnosis and redescription of P. cyclostoma is provided for the first time, including data on infraciliature and molecular sequence. Phylogenetic analyses revealed that the three species cluster together and with the sequence of a Chinese population of P. vestita already present in the GenBank database, forming a robust clade.

Integrative data of a novel ciliate (Alveolata, Ciliophora) propose the establishment of Heterodeviata nantongensis nov. sp

BACKGROUND

As unicellular eukaryotes, ciliates are an indispensable component of micro-ecosystems that play the role of intermediate nutrition link between bacteria or algae and meiofauna. Recent faunistic studies have revealed 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 that it represents a new species.

RESULTS

The morphology and morphogenesis of the new brackish-water deviatid ciliate, Heterodeviata nantongensis nov. sp., isolated from Nantong, China, were investigated using live observations and protargol staining. The diagnostic traits of the new species include three frontal cirri, one buccal cirrus, one or two parabuccal cirri, an inconspicuous frontoventral cirral row of four to six frontoventral cirri derived from two anlagen, three left and two right marginal rows, two dorsal kineties, dorsal kinety 1 with 9-14 dikinetids and dorsal kinety 2 with only two dikinetids, and one to three caudal cirri at the rear end of dorsal kinety 1. 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) five cirral anlagen are formed in both proter and opisthe; (v) in the proter, anlagen I and II very likely originate from the parental undulating membranes and the buccal cirrus, respectively, anlage III from anterior parabuccal cirrus, anlage IV originates from the parental frontoventral cirri and anlage V from the innermost parental right marginal row; and (vi) anlagen I-IV of the opisthe are all generated from oral primordium, anlage V from the innermost parental right marginal row. Phylogenetic analyses based on SSU rRNA gene sequence data were performed to determine the systematic position of the new taxon.

CONCLUSIONS

The study on 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 provides a reliable reference for environmental monitoring and resource investigations.