More amoebae from the deep-sea: Two new marine species of Vexillifera (Amoebozoa, Dactylopodida) with notes on taxonomy of the genus

A New Mayorella Species Isolated from the Mariana Trench Area (Pacific Ocean)

In this paper, we describe a new naked amoeba species, Mayorella marianaensis sp. n., order Dermamoebida, isolated from the bottom of the Pacific Ocean (>3,000 m depth) in the vicinity of the Mariana Trench, based on morphological and molecular data. The newly discovered species was identified based on morphological and molecular data. This is the first time that a Mayorella species was discovered in the deep sea (>1,000 m). Mayorella marianaensis is an irregularly rectangular naked amoeba (30-120 × 11-60 µm), with a narrow frontal hyaline area. Four to 15 conical sub-pseudopodia, and three kinds of floating forms are identified. Trophozoites have a thick cell coat consisting of two distinct layers. The small subunit ribosomal RNA gene phylogeny showed that M. marianaensis is classified into Dermamoebida, and is a sister clade to other Mayorella species whose sequences are available. BLAST analysis revealed that M. marianaensis is most similar to Coronamoeba villafranca and Mayorella sp. JJP-2003, with sequence identities of 92.43% and 88.30%, respectively.

Ovalopodium rosalinum sp. nov., Planopodium haveli gen. nov, sp. nov., Planopodium desertum comb. nov. and new insights into phylogeny of the deeply branching members of the order Himatismenida (Amoebozoa)

The order Himatismenida (Amoebozoa, Discosea) comprises naked amoebae with an organic coat that is located on the dorsal surface of the cell. The phylogenetic relationships among deeply branching genera of the Himatismenida are unclear, as data on the species diversity of the himatismenid genera is largely restricted to the derived genus Cochliopodium. Here, we describe two new amoeba species that branch at the base of the order Himatismenida, evidenced by SSU rRNA gene and multigene analyses. Among them, a freshwater species Planopodium haveli gen. nov., sp. nov. has a dorsal cell coat consisting of flat, oval scales. This species forms a clade at the base of the Himatismenida, and the previously described Ovalopodium desertum, its closest relative, is transferred into the new genus as Planopodium desertum comb. nov. Although the two species are barely distinguishable by their sequence data, they are clearly distinct in morphology. Using this data, we can report the first evidence of a dorsal cell coat consisting of scales outside of the genus Cochliopodium. The other species has a marine origin and branches deeply, close to the root of the phylogenetic tree of Himatismenida. Based on the morphology of this amoeba, it should be described as Ovalopodium rosalinum sp. nov., a new species of the genus Ovalopodium. Analyses of the phylogenetic relationships and the ultrastructure of the deeply branching himatismenids, together with several of the newly obtained gene sequences of Parvamoeba and Cochliopodium, suggest that some elements of the dorsal cell coat of Ovalopodium may be ancestral for Himatismenida and have been partly retained in various more derived species of this clade, in particular, Cochliopodium gallicum. Although actin and Cox1 gene data do not resolve the higher-level relationships in Himatismenida, they correspond to the grouping of species within most genera.

Protist diversity and function in the dark ocean - Challenging the paradigms of deep-sea ecology with special emphasis on foraminiferans and naked protists

The dark ocean and the underlying deep seafloor together represent the largest environment on this planet, comprising about 80% of the oceanic volume and covering more than two-thirds of the Earth's surface, as well as hosting a major part of the total biosphere. Emerging evidence suggests that these vast pelagic and benthic habitats play a major role in ocean biogeochemistry and represent an "untapped reservoir" of high genetic and metabolic microbial diversity. Due to its huge volume, the water column of the dark ocean is the largest reservoir of organic carbon in the biosphere and likely plays a major role in the global carbon budget. The dark ocean and the seafloor beneath it are also home to a largely enigmatic food web comprising little-known and sometimes spectacular organisms, mainly prokaryotes and protists. This review considers the globally important role of pelagic and benthic protists across all protistan size classes in the deep-sea realm, with a focus on their taxonomy, diversity, and physiological properties, including their role in deep microbial food webs. We argue that, given the important contribution that protists must make to deep-sea biodiversity and ecosystem processes, they should not be overlooked in biological studies of the deep ocean.

Cunea russae n. sp. (Amoebozoa, Dactylopodida), another cryptic species of Cunea Kudryavtsev and Pawlowski, 2015, inhabits a continental brackish-water biotope

The genus Cunea Kudryavtsev and Pawlowski, 2015 (Amoebozoa, Dactylopodida) was initially described from the oceanic benthos: C. profundata, from over 5 km depth in the Atlantic Ocean, and C. thuwala from the Red Sea benthos at ca. 60 m depth. Both species are identical to each other in morphology (including cell coat ultrastructure), but differ significantly in the gene sequence data, including barcoding loci of small subunit ribosomal RNA and cytochrome oxidase subunit 1 gene, as well as actin. This paper describes the third species of Cunea, C. russae n. sp. isolated from a brackish water habitat without a direct connection to the ocean, a small spring of brackish water (19‰) emerging from a 246 m deep hole in the earth. This species is morphologically identical to the previous two amoebae, but differs from them significantly in the gene sequence data and ecological preferences. In particular, this species has the broadest salinity tolerance range, being able to reproduce well already at 2.5‰. It is also capable of resisting cold temperatures, like C. profundata. The data obtained suggest that the genus Cunea may comprise a significant taxonomic diversity represented by morphologically identical, but quickly diverging species with significant ecological plasticity.