Rhizarian ‘Novel Clade 10’ Revealed as Abundant and Diverse Planktonic and Terrestrial Flagellates, including Aquavolon n. gen.

Abstract

Rhizarian ‘Novel Clade 10’ (NC10) is frequently detected by 18S rRNA gene sequencing studies in freshwater planktonic samples. We describe a new genus and two species of eukaryovorous biflagellate protists, Aquavolon hoantrani n. gen. n. sp. and A. dientrani n. gen. n. sp., which represent the first morphologically characterized members of NC10, here named Aquavolonida ord. nov. The slightly metabolic cells possess naked heterodynamic flagella, whose kinetosomes lie at a right angle to each other and are connected by at least one fibril. Unlike their closest known relative Tremula longifila, they rotate around their longitudinal axis when swimming and only very rarely glide on surfaces. Screening of a wide range of environmental DNA extractions with lineage‐specific PCR primers reveals that Aquavolonida consists of a large radiation of protists, which are most diversified in freshwater planktonic habitats and as yet undetected in marine environments. Earlier‐branching lineages in Aquavolonida include less frequently detected organisms from soils and freshwater sediments. The 18S rRNA gene phylogeny suggests that Aquavolonida forms a common evolutionary lineage with tremulids and uncharacterized ‘Novel Clade 12’, which likely represents one of the deepest lineages in the Rhizaria, separate from Cercozoa (Filosa), Endomyxa, and Retaria.

Distinct communities of Cercozoa at different soil depths in a temperate agricultural field

“…Numerous anoxic groups of protists are only known from environmental sequences, and thus not yet described (see for instance ‗Novel Clade 12' in Bass et al (2018)). Traditional culturebased approaches are still required to fill this gap in our knowledge (Dumack et al 2016).…”

Making sense of environmental sequencing data: Ecologically important functional traits of the protistan groups Cercozoa and Endomyxa (Rhizaria)

“…The main taxonomic subdivisions are: (a) Endomyxa including Vampyrellida, Phytomyxea, Filoreta , Gromia and Ascetosporea (Bass et al, ; Sierra et al, ); (b) Cercozoa including the classes Sarcomonadea, Thecofilosea, Granofilosea, Imbricatea, Chlorarachnea and Metromonadea (Cavalier‐Smith et al, ); and (c) the incertae sedis rhizarian clades Aquavolonida, Tremulida and Novel Clade 12 (Bass et al, ).…”

Contrasting Responses of Protistan Plant Parasites and Phagotrophs to Ecosystems, Land Management and Soil Properties

“…Cercozoa ( Cavalier-Smith, 1998 ), a highly diverse phylum of c. 600 described species ( Pawlowski et al, 2012 ), is a major protistan lineage in soil ( Geisen et al, 2015 ; Grossmann et al, 2016 ; Lanzén et al, 2016 ; Ferreira de Araujo et al, 2018 ), comprising a vast array of functional traits in morphologies, nutrition and locomotive modes ( Burki and Keeling, 2014 ). Recently the phylum Endomyxa was separated from Cercozoa ( Bass et al, 2018 ; Cavalier-Smith et al, 2018 ), and it is of particular interest for containing inter alia plant pathogens of functional and economic significance, including important transmitters of plant viruses and agents of root tumors (e.g., club root disease) ( Neuhauser et al, 2014 ; Bass et al, 2019 ).…”