Amoeboid protists are extremely abundant and diverse in natural systems where they often play outstanding ecological roles. They can be found in almost all major eukaryotic divisions, and genomic approaches are bringing major changes in our perception of their deep evolutionary relationships. At fine taxonomic levels, the generalization of barcoding is revealing a considerable and unsuspected specific diversity that can be appreciated with careful morphometric analyses based on light and electron microscopic observations. We provide examples on the difficulties and advances in amoeboid protists systematics in a selection of groups that were presented at the VIIIth ECOP/ISOP meeting in Rome, 2019. We conclude that, in all studied groups, important taxonomical rearrangements will certainly take place in the next few years, and systematics must be adapted to incorporate these changes. Notably, nomenclature should be flexible enough to integrate many new high level taxa, and a unified policy must be adopted to species description and to the establishment of types.
- MeSH
- Amoebozoa classification MeSH
- Biodiversity MeSH
- Classification * MeSH
- Terminology as Topic MeSH
- Research trends MeSH
- Publication type
- Congress MeSH
Neoparamoeba perurans is the aetiological agent of amoebic gill disease (AGD) in salmonids, however multiple other amoeba species colonise the gills and their role in AGD is unknown. Taxonomic assessments of these accompanying amoebae on AGD-affected salmon have previously been based on gross morphology alone. The aim of the present study was to document the diversity of amoebae colonising the gills of AGD-affected farmed Atlantic salmon using a combination of morphological and sequence-based taxonomic methods. Amoebae were characterised morphologically via light microscopy and transmission electron microscopy, and by phylogenetic analyses based on the 18S rRNA gene and cytochrome oxidase subunit I (COI) gene. In addition to N. perurans, 11 other amoebozoans were isolated from the gills, and were classified within the genera Neoparamoeba, Paramoeba, Vexillifera, Pseudoparamoeba, Vannella and Nolandella. In some cases, such as Paramoeba eilhardi, this is the first time this species has been isolated from the gills of teleost fish. Furthermore, sequencing of both the 18S rRNA and COI gene revealed significant genetic variation within genera. We highlight that there is a far greater diversity of amoebae colonising AGD-affected gills than previously established.
- MeSH
- Amebiasis parasitology veterinary MeSH
- Amoebozoa classification genetics ultrastructure MeSH
- Biodiversity * MeSH
- Phylogeny MeSH
- Microscopy MeSH
- Fish Diseases parasitology MeSH
- Electron Transport Complex IV genetics MeSH
- RNA, Ribosomal, 18S genetics MeSH
- Salmo salar parasitology MeSH
- Microscopy, Electron, Transmission MeSH
- Gills parasitology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
Two amoeboid organisms of the genera Sappinia Dangeard, 1896 and Rosculus Hawes, 1963 were identified in a sample containing king penguin guano. This sample, collected in the Subantarctic, enlarges the list of fecal habitats known for the presence of coprophilic amoebae. The two organisms were co-isolated and subcultured for over 6 mo, with continuous efforts being invested to separate each one from the mixed culture. In the mixed culture, Rosculus cells were fast growing, tolerated changes in culturing conditions, formed cysts, and evidently were attracted by Sappinia trophozoites. The separation of the Rosculus strain was accomplished, whereas the Sappinia strain remained intermixed with inseparable Rosculus cells. Sappinia cell populations were sensitive to changes in culturing conditions; they improved with reduction of Rosculus cells in the mixed culture. Thick-walled cysts, reportedly formed by Sappinia species, were not seen. The ultrastructure of both organisms was congruent with the currently accepted generic characteristics; however, some details were remarkable at the species level. Combined with the results of phylogenetic analyses, our findings indicate that the ultrastructure of the glycocalyx and the presence/absence of the Golgi apparatus in differential diagnoses of Sappinia species require a critical re-evaluation.
- MeSH
- Amoebozoa classification genetics isolation & purification ultrastructure MeSH
- Cercozoa classification genetics isolation & purification ultrastructure MeSH
- Ecosystem MeSH
- Feces parasitology MeSH
- Phylogeny MeSH
- Spheniscidae parasitology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Georgia MeSH
Five amoeboid organisms of different origin (isolated from fish organs, soil and digestive tract of earthworm) that shared light microscopical and ultrastructural features including type and arrangement of mitochondrial cristae were subjected to phylogenetic analyses based on sequences of SSU rDNA and protein coding genes (actin, cytochrome oxidase I, and eukaryotic elongation factor 2). The reconstruction of multigene phylogeny of the strains studied (i) revealed that they belong to the same single-genus Copromyxa clade; (ii) strongly supported position of Copromyxa cantabrigiensis (syn. Hartmannella cantabrigiensis) within the genus; (iii) together with comparisons of light and electron microscopy data justified reclassification of Cashia limacoides (syn. Vexillifera expectata) to Copromyxa limacoides n. comb., and (iv) justified description of a new species, Copromyxa laresi n. sp.
- MeSH
- Actins genetics MeSH
- Amoeba MeSH
- Amoebozoa classification genetics isolation & purification ultrastructure MeSH
- Zebrafish parasitology MeSH
- Species Specificity MeSH
- Microscopy, Electron MeSH
- Phylogeny * MeSH
- Elongation Factor 2 Kinase genetics MeSH
- Lobosea classification genetics isolation & purification ultrastructure MeSH
- Mitochondria parasitology ultrastructure MeSH
- Oligochaeta parasitology MeSH
- Organelles parasitology ultrastructure MeSH
- DNA, Protozoan genetics MeSH
- Protozoan Proteins genetics MeSH
- Soil parasitology MeSH
- Electron Transport Complex IV genetics MeSH
- DNA, Ribosomal genetics MeSH
- Base Sequence MeSH
- Sequence Alignment MeSH
- Gills parasitology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Geographicals
- Czech Republic MeSH
- Spain MeSH
A new amoebozoan species, Vermistella arctica n. sp., is described from marine habitats in the central part of Svalbard archipelago. This is the first report on Arctic amoebae belonging to the genus Vermistella Moran and Anderson, 2007, the type species of which was described from the opposite pole of the planet. Psychrophily proved in the new strains qualifies the genus Vermistella as a bipolar taxon. Molecular phylogenetic analyses based on 18S rDNA and actin sequences did not show any affinity of the genus Vermistella to Stygamoeba regulata ATCC(®) 50892(™) strain. A close phylogenetic relationship was found between Vermistella spp. and a sequence originating from an environmental sample from Cariaco basin, the largest marine permanently anoxic system in the world. Possible mechanisms of bipolar distribution are discussed.
- MeSH
- Actins genetics MeSH
- Amoeba genetics MeSH
- Amoebozoa classification genetics isolation & purification ultrastructure MeSH
- Phylogeny MeSH
- Phylogeography MeSH
- Lobosea MeSH
- Seawater parasitology MeSH
- DNA, Protozoan genetics MeSH
- DNA, Ribosomal genetics MeSH
- RNA, Ribosomal, 16S genetics MeSH
- Cold Climate MeSH
- Microscopy, Electron, Transmission MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Arctic Regions MeSH
- Svalbard MeSH
The genus Rhizomastix is a poorly known group of amoeboid heterotrophic flagellates living as intestinal commensals of insects, amphibians or reptiles, and as inhabitants of organic freshwater sediments. Eleven Rhizomastix species have been described so far, but DNA sequences from only a single species have been published. Recently, phylogenetic analyses confirmed a previous hypothesis that the genus belongs to the Archamoebae; however, its exact position therein remains unclear. In this study we cultured nine strains of Rhizomastix, both endobiotic and free-living. According to their light-microscopic morphology and SSU rRNA and actin gene analyses, the strains represent five species, of which four are newly described here: R. bicoronata sp. nov., R. elongata sp. nov., R. vacuolata sp. nov. and R. varia sp. nov. In addition, R. tipulae sp. nov., living in the intestine of crane flies, is separated from the type species, R. gracilis. We also examined the ultrastructure of R. elongata sp. nov., which revealed that it is more complicated than the previously described R. libera. Our data show that either the endobiotic lifestyle of some Rhizomastix species has arisen independently from other endobiotic archamoebae, or the free-living members of this genus represent a secondary switch from the endobiotic lifestyle.
- MeSH
- Actins genetics MeSH
- Amoebozoa classification genetics isolation & purification ultrastructure MeSH
- Species Specificity MeSH
- Phylogeny MeSH
- Genes, rRNA MeSH
- Geologic Sediments parasitology MeSH
- Microscopy MeSH
- DNA, Protozoan analysis MeSH
- Base Sequence MeSH
- Sequence Analysis, DNA MeSH
- Fresh Water parasitology MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
A total of 109 sea urchins from 3 species collected in 2 localities off the coast of Tenerife Island, Spain, were examined for the presence of free-living amoebae in their coelomic fluid. Amoeba trophozoites were isolated exclusively from moribund individuals of long-spined sea urchins Diadema aff. antillarum (Philippi) (Echinoidea, Echinodermata) that manifested lesions related to sea urchin bald disease on their tests (16 out of 56 examined). No amoebae were detected in Arbacia lixula (L.) and Paracentrotus lividus (Lamarck). From the former sea urchin species, 8 strains, established from 10 primary isolates, were identified as Neoparamoeba branchiphila Dyková et al., 2005 using morphological and molecular methods. Results of this study (limited to the screening for free-living amoebae) together with data on agents of sea urchin mortalities reported to date justify the hypothesis that free-living amoebae play an opportunistic role in D. aff. antillarum mortality. The enlargement of the dataset of SSU rDNA sequences brought new insight into the phylogeny of Neoparamoeba species.
- MeSH
- Amoebozoa classification genetics isolation & purification MeSH
- Phylogeny MeSH
- Sea Urchins parasitology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Atlantic Ocean MeSH
- Spain MeSH
Testate amoebae (TA) are a group of free-living protozoa, important in ecology and paleoecology. Testate amoebae taxonomy is mainly based on the morphological features of the shell, as examined by means of light microscopy or (environmental) scanning electron microscopy (SEM/ESEM). We explored the potential applications of confocal laser scanning microscopy (CLSM), two photon excitation microscopy (TPEM), phase contrast, differential interference contrast (DIC Nomarski), and polarization microscopy to visualize TA shells and inner structures of living cells, which is not possible by SEM or environmental SEM. Images captured by CLSM and TPEM were utilized to create three-dimensional (3D) visualizations and to evaluate biovolume inside the shell by stereological methods, to assess the function of TA in ecosystems. This approach broadens the understanding of TA cell and shell morphology, and inner structures including organelles and endosymbionts, with potential implications in taxonomy and ecophysiology.
A strain of naked amoeba isolated from pikeperch (Sander lucioperca (L.)) kidney tissue has been characterized using light- and transmission electron microscopy. Sequencing of SSU rDNA and phylogenetic analysis based on a broad dataset of sequences completed our study. All data obtained suggest that this strain belongs to a species that has not been described before. As none of the existing genera of amoebae is applicable to this organism, the new genus Grellamoeba is established and the type species Grellamoeba robusta is described. Although the phylogenetic position of the SSU rDNA sequence of the type strain of G. robusta is sensitive to the method of analysis applied, a tendency to group with Acramoeba dendroida Smirnov, Nassonova et Cavalier-Smith, 2008 is evident.
- MeSH
- Amoebozoa classification genetics isolation & purification ultrastructure MeSH
- Phylogeny MeSH
- Genes, rRNA MeSH
- Kidney parasitology MeSH
- Microscopy MeSH
- Molecular Sequence Data MeSH
- Perches parasitology MeSH
- DNA, Protozoan chemistry genetics MeSH
- DNA, Ribosomal chemistry genetics MeSH
- RNA, Protozoan genetics MeSH
- RNA, Ribosomal, 18S genetics MeSH
- Sequence Analysis, DNA MeSH
- Cluster Analysis MeSH
- Microscopy, Electron, Transmission MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
