Triangulopteris lacunata gen. et sp. nov. (Centroplasthelida), a New Centrohelid Heliozoan from Soil

Abstract

A new genus and species of centrohelid heliozoans, Triangulopteris lacunata gen. et sp. nov. (Pterocystidae Cavalier-Smith and Heyden, 2007), from four geographically remote locations (the Crimean Peninsula, the Dnieper Lowland (the East European Plain), Franz Josef Land, and the Kolyma Lowland (North–Eastern Siberia) was examined using light and electron microscopy. The novel centrohelid is characterized by round shape, 4.3–16.3 μm in diameter, covered with two types of scales: 1.06–4.54 μm long triangular spine scales and 1.22–2.05 μm oval plate scales. Studied centrohelid heliozoan possesses a unique spine scale morphology. The base of scales is represented by a horse hoof-shaped basal plate. The inner surface and lateral wings of spine scales have numerous radial ribs with two ‘pockets’ that are located on both sides of the spine shaft. These pockets are formed by the lateral wings and ends of the basal plate. The cyst formation and transition to a spicules-bearing stage were noted. Additionally, phylogenetic tree was constructed based on SSU rRNA sequences including the strain HF-25 from the permafrost of Kolyma Lowland. The resulting phylogeny recovered it within the clade Pterista, while forming a separate sister lineage to H2 clade, which only had included freshwater environmental sequences.

On the phylogenetic position of Raphidocystis pallida with some notes on its life cycle

“…Recently, it has been shown that some of the centrohelids are capable of alternating between different coverings types with distinct morphologies in the course of their life cycles (Drachko et al, 2020; Zagumyonnyi et al, 2021; Zlatogursky et al, 2018). In particular, Raphidocystis glabra Dürrschmidt, 1985 was shown to form a spicule‐bearing stage in addition to originally described stage covered with siliceous scales (Zlatogursky et al, 2018).…”

Unexpected ubiquity of heart‐shaped scale morphotype in Centroplasthelida (Haptista): Ancestral trait or multiple acquisitions?

“…They are absent only in naked Oxnerella (Cavalier-Smith & Chao, 2012;Dobell, 1917) and mucous-covered Chlamydaster (Dürrschmidt & Patterson, 1987a). The commonly believed assumption that there are species with only organic spicules as coverings (e.g., Heterophrys and Sphaerastrum) is now challenged by a discovery of scales/spicules alternation in many species (Zagumyonnyi et al, 2021(Zagumyonnyi et al, , 2022Zlatogursky, 2016;Zlatogursky et al, 2018). In light of these discoveries, it is possible that all the Heterophryslike organisms have cryptic scale-bearing stages.…”

“…Centrohelids are characterized by ribbon‐shaped mitochondrial cristae, axopodia radiating from tripartite microtubules‐organizing centers (Cavalier‐Smith & Chao, 2012), and ball+cone element‐containing extrusomes (Sakaguchi et al, 2002). Centrohelid heliozoans inhabit benthos and periphyton of freshwater (Gerasimova & Plotnikov, 2016; Prokina & Mylnikov, 2019; Zlatogursky, 2013), marine (Prokina et al, 2019; Shɨshkin et al, 2018), and hypersaline ecosystems (Gerasimova et al, 2020; Plotnikov & Gerasimova, 2017), as well as soil (Cavalier‐Smith & von der Heyden, 2007; Zagumyonnyi et al, 2021). Centrohelid heliozoans along with haptophytes constitute the Haptista supergroup (Burki et al, 2016).…”

Aquatic Biodiversity: Evolution, Taxonomy and Conservation

“…They have thoroughly described Parafumarolamoeba stagnalis from a small pond in European Russia based on fine morphology using light and electron microscopy, and reconstructed the molecular phylogenies based on the SSU rRNA and ITS loci. Zagumyonnyi et al [2] revealed a new genus and species of centrohelid heliozoans, Triangulopteris lacunata (Pterocystidae) that is broadly distributed from the East European Plain to the North-Eastern Siberia. Authors used morphological (light and electron microscopy) methods as well as phylogenetic approaches (SSU rRNA) to identify the novel lineage and its phylogenetic position.…”