Pinjata ruminata gen. et sp. n.—A New Member of Centrohelid Family Yogsothothidae (Haptista: Centroplasthelida) from the Brackish River

Abstract

A new genus and species of centrohelid heliozoan Pinjata ruminata from the Tuzlukkol’ River (Orenburg Region of Russia) and Gorʼkoe Lake (Chelyabinsk Region of Russia) is studied with light‐ and electron microscopy. Pinjata ruminata has two types of plate scales, partially running up the sides of the axopodia. Inner plate scales (3.2–4.9 × 1.5–2.6 μm) are flat, ovate‐oblong and have a broad axial thickening and a thin electron‐dense border. Outer plate scales (4.2–6.7 × 1.5–3.0 μm) are concave, elongated, of irregular shape, often curved, and broadened towards one end. Roundish depressions are forming two rows on both sides of the narrow axial thickening. The cells are attached to the substratum. Molecular phylogenetic analysis based on the SSU rDNA robustly placed P. ruminata in the family Yogsothothidae. This position is confirmed with the presence of five panacanthocystid increase regions. The morphology of the new genus is in a good accordance with diagnosis of the family. The status of a genus “Heteroraphidiophrys” is discussed. Other potential findings of Pinjata from literature are analyzed. Pinjata represents the third lineage of centrohelids, characterized with the presence of only tangentially oriented plate scales. The halophilic nature of Yogsothothidae is suggested.

Clypifer cribrifer gen. nov., sp. nov. (Clypiferidae fam. nov., Pterocystida, Centroplasthelida), with notes on evolution of centrohelid siliceous coverings

“…Raineriophrys Mikrjukov 2001. All this corroborates the fact that the LCA was able to form coverings similar to those of Pinjata Gerasimova, Shɨshkin and Zlatogursky 2019 [21]. If this alternative is true, the coverings of C. cribrifer might represent a secondary simplification.…”

“…Alternatively, the LCA could have scales of two non-significantly differentiated types, as in the recently described Pinjata ruminata Gerasimova, Shɨshkin and Zlatogursky 2019 [21]. The slight asymmetry of the outer scales is traceable in P. ruminata (Figs 1e, f and 3c; of [21]). In these scales, the biggest roundish depression is always at one end resembling some Pterocystidae, e.g.…”

“…The LCA might have coverings with one layer of undifferentiated siliceous scales; given that C. cribrifer has scales of primarily one type. In this scenario, scales underwent diversification into two types at least three times in the evolution of centrohelids-in Alternatively, the LCA could have scales of two non-significantly differentiated types, as in the recently described Pinjata ruminata Gerasimova, Shɨshkin and Zlatogursky 2019 [21]. The slight asymmetry of the outer scales is traceable in P. ruminata (Figs 1e, f and 3c; of [21]).…”

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

“…The morphotypes without spine scales (some Raphidocystidae, Raphidiophryidae, and Clypiferidae) most probably originated through the loss of the spine scales and evolving more complex plate scales (Shishkin et al, 2021). Potentially spine scales could be also lost in Yogsothothidae with subsequent differentiation of plate scales into two types (like in Pinjata ) and further into boat‐ or helmet‐shaped scales, forming an outer layer ( Yogsothoth ; Shɨshkin et al, 2018; Zlatogursky et al, 2019). The acquisition of spine scales with a radially symmetrical circular base, which is the case for all the Chalarothoracina with spine scales known, could be through fusion of the notch edges in the heart‐shaped base, as was hypothesized by Mikrjukov (1997).…”

Silica‐scaled heterotrophic protists Rotosphaerida, Thaumatomonadida, and Centroplasthelida in the large continuous ecosystem connecting Lake Baikal to the Kara Sea

“…Molecular biological methods allow the identification of species with elevated accuracy, discovery of new taxa, and description of the characteristics of evolution of heterotrophic protists (Adl et al, 2019; Cavalier‐Smith & Chao, 2012; Nikolaev et al, 2004; Shɨshkin et al, 2018; Zlatogursky et al, 2019). The standard accepted method for determining the diversity of silica‐scaled heterotrophic protists in the wild is electron microscopy (EM) which can identify taxa by the features of the structural elements of their frustules, such as the shape of the basement of radial scales, number and shape of pikes at their tops, and shape and surface topography of lamellate scales, as well as other details (Gerasimova & Plotnikov, 2016; Leonov & Mylnikov, 2012; Prokina et al, 2021; Siemensma, 1991; Zlatogursky, 2010).…”