Dermamoeba algensis n. sp. (Amoebozoa, Dermamoebidae) – An algivorous lobose amoeba with complex cell coat and unusual feeding mode

Coronamoeba villafranca gen. nov. sp. nov. (Amoebozoa, Dermamoebida) challenges the correlation of morphology and phylogeny in Amoebozoa

Coronamoeba villafranca gen. nov. sp. nov. is a small amoeba isolated from the surface planktonic biotope in the Bay of Villefranche (Mediterranean Sea). It has a confusing set of morphological and molecular characters. Its locomotive form is subcylindrical and monopodial with monoaxial cytoplasmic flow and occasional hyaline bulging at the anterior edge (a monotactic morphotype). Based on this set of characters, this amoeba is most similar to members of the genus Nolandella (Tubulinea, Euamoebida). However, molecular phylogenetic analysis based on only the small subunit ribosomal RNA (SSU rRNA) gene and on two concatenated markers (SSU rRNA gene and actin) robustly places this species in the Discosea, specifically, in a clade with Dermamoeba and Paradermamoeba (Dermamoebida) as the closest described relatives, and several SSU rRNA clones from environmental DNA. A unique glycocalyx of the studied amoeba consisting of complex separate units with pentameric symmetry may be considered a unifying character of this species with other dermamoebids. The monotactic morphotype demonstrated by these amoebae primarily occurs in Tubulinea but was recently confirmed in other clades of Amoebozoa (e.g. Dactylopodida and Variosea). This morphotype may be the plesiomorphic mode of cell organization in Amoebozoa that might have evolved in the last amoebozoan common ancestor (LACA) and conserved in several lineages of this group. It may reflect basic characteristics of the cytoskeletal structure and functions in Amoebozoa.

New data on the fine structure of Deuteramoeba mycophaga CCAP 1586/1 (Amoebozoa, Tubulinea)

The genus Deuteramoeba is one of the six amoebae genera belonging to the best-known amoeba family - Amoebidae (Amoebozoa, Tubulinea), containing such a popular species as Amoeba proteus. However, members of other genera of the family Amoebidae are much less known, and most of the studies of their morphology and ultrastructure date back to the 1970s and 1980s. Since these "classical" species are believed to be "well studied", their morphology and fine structure rarely become a subject of re-investigation. The absence of modern morphological data may be critical when molecular data of the type strain are not available, and the only way to identify a species is by morphological comparison. For this paper, we performed an ultrastructural study of the strain CCAP 1586/1 - the type strain of the species Deuteramoeba mycophaga. Our study revealed new details of the nuclear structure, including a peripheral layer of filaments and a heterogeneous nucleolus, and provided new data on the cytoplasmic inclusions of this species. We performed a whole-genome amplification of the DNA from a single amoeba cell followed by NGS sequencing and searched for genetic evidence for the presence of a putative nuclear parasite detected in 2017, but found no evidence for the presence of Opisthosporidia.

The Efficiency of Cultivation Media in Recovering Naked Lobose Amoebae from Freshwater Environments

Martin Mrva and Mária Garajová (2018) This paper deals with the efficiency of cultivation media in recovering the species diversity of naked lobose amoebae. A total of 24 species belonging to ten families were isolated with six enrichment media (two liquid and four agar media) during a two-year study on naked lobose amoebae in a branch of the Danube River in Bratislava (Slovak Republic). The highest efficiency was seen in the grass-seed infusion, grass-seed agar, and non-nutrient agar, with 79%, 67%, and 58% of species recovered, respectively. The grass-seed infusion yielded the highest numbers of Thecamoebidae, Vannellidae, Mayorellidae and Dermamoebidae species and is likely the most suitable medium for their recovery. The most effective media were based on grass-seed infusions, which are easy to prepare and suitable for studying the diversity and ecology of naked amoebae from freshwater samples.

Mycamoeba gemmipara nov. gen., nov. sp., the First Cultured Member of the Environmental Dermamoebidae Clade LKM74 and its Unusual Life Cycle

Since the first environmental DNA surveys, entire groups of sequences called "environmental clades" did not have any cultured representative. LKM74 is an amoebozoan clade affiliated to Dermamoebidae, whose presence is pervasively reported in soil and freshwater. We obtained an isolate from soil that we assigned to LKM74 by molecular phylogeny, close related to freshwater clones. We described Mycamoeba gemmipara based on observations made with light- and transmission electron microscopy. It is an extremely small amoeba with typical lingulate shape. Unlike other Dermamoebidae, it lacked ornamentation on its cell membrane, and condensed chromatin formed characteristic patterns in the nucleus. M. gemmipara displayed a unique life cycle: trophozoites formed walled coccoid stages which grew through successive buddings and developed into branched structures holding cysts. These structures, measuring hundreds of micrometres, are built as the exclusive product of osmotrophic feeding. To demonstrate that M. gemmipara is a genuine soil inhabitant, we screened its presence in an environmental soil DNA diversity survey performed on an experimental setup where pig cadavers were left to decompose in soils to follow changes in eukaryotic communities. Mycamoeba gemmipara was present in all samples, although related reads were uncommon underneath the cadaver.

New data on the ultrastructure of Paradermamoeba levis (Amoebozoa, Discosea, Dermamoebida): Cytoplasmic MTOCs are found among Dermamoebida

In this detailed electron microscopic study of Paradermamoeba levis Smirnov et Goodkov 1994 (phylum Amoebozoa, class Discosea, subclass Longamoebia, order Dermamoebida, family Dermamoebidae) based on numerous fixations and studies of a large number of cells we provide the first comprehensive description of the ultrastructure of this species. P. levis possesses cytoplasmic microtubule-organizing centres (MTOCs) associated with dictyosomes of the Golgi complex. This finding adds evidence to our earlier suggestion that the presence of cytoplasmic MTOCs is a synapomorphy of the phylogenetic lineages forming the subclass Longamoebia. The so-called "supernumerary nucleus" of P. levis noted in the initial description was found to be not an individual structure but an outgrowth of the cell nucleus containing its own nucleolus. Enigmatic trichocyst-like bodies were noted in all studied strains, originating from different geographic locations. This proves that these bodies are integral parts of the cell structure, not an occasional property of the type strain. P. levis is now reliably recorded from several European locations (North-Western Russia, Croatia, Switzerland, UK) and Far East of Russia.

Sapocribrum chincoteaguense n. gen. n. sp.: A Small, Scale-bearing Amoebozoan with Flabellinid Affinities

The isolate American Type Culture Collection (ATCC)® 50979™ is a small amoebozoan whose actin gene was previously characterized, but did not allow a stable phylogenetic placement. This isolate was originally mis-identified upon deposition, and subsequently mis-illustrated in a recent publication. Here, we provide both a detailed morphological description as well as additional molecular analyses in order to clarify the isolate's phylogenetic relationships. The amoeba is minute (less than 5 μm), and presents the behavior of staying in a fixed location, while emitting one or two thin pseudopods. Transmission electron microscopy reveals that the cell is covered in a layer with embedded scales, giving the cell an armored appearance. Molecular phylogenetic analyses of data (actin, alpha- and beta-tubulin, elongation factor 2, and 14-3-3) from transcriptomes of this and four other isolates reveals that ATCC® 50979(™) is closely related to the recently described Squamamoeba japonica and in a novel, stable clade. Due to the unique nature of the scale covering, as well as other gross morphological characters and the molecular phylogenetic analyses, we formally describe the isolate as Sapocribrum chincoteaguense n. gen. n. sp.