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J Eukaryot Microbiol. 2016 Mar-Apr;63(2):181-97. doi: 10.1111/jeu.12266. Epub 2015 Sep 26.

Morphological and Molecular Diversity of the Neglected Genus Rhizomastix Alexeieff, 1911 (Amoebozoa: Archamoebae) with Description of Five New Species.

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Department of Zoology, Faculty of Science, Charles University in Prague, Vinicna 7, 128 44, Prague, Czech Republic.
Centre for Epidemiology and Microbiology, National Institute of Public Health, Srobarova 48, 100 42, Prague, Czech Republic.
Department of Parasitology, Faculty of Science, Charles University in Prague, Vinicna 7, 128 44, Prague, Czech Republic.
Equipe Diversité et Évolution Microbiennes, Laboratoire Ecologie, Systématique et Evolution, UMR 8079 CNRS-UPS-AgroParisTech, Université de Paris-Sud, Bâtiment 360, 91405, Orsay, France.


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.


Archamoebae; morphology; phylogeny; ultrastructure

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