CC BY
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Protistology ■ 83
1 - Unité d'Ecologie, Systématique et Evolution, Université Paris-Sud 11, France
2 - Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Catalunya
3 - Institució Catalana de Recerca i Estudis Avangats (ICREA)
Opisthokonts, one of the largest eukaryotic supergroups, is divided into two major clades: the Holozoa, encompassing animals and their unicellular relatives, and the Holomycota, including fungi and their unicellular relatives. The earliest-branching lineage in Holomycota, which has received many names (e.g. Nucleariidae, Cristidiscoidia, Discicristata), remains poorly studied. This group of phagotrophic filose amoebae bears contrasting features in comparison with those of their close relatives, the parasitic Opisthosporidia and the osmotrophic fungi. It originally contained a single genus, Nuclearia, which includes naked amoebae of ca. 40 ^m cell diameter that feed on filamentous cyanobacteria in freshwater environments. More recently, Fonticula alba was included as sister to Nuclearia spp. With much smaller cell size and bacterivore, this amoeba presents an aggregative multicellular fruiting body. Here we describe the new genus Parvularia nov. gen., a small filose amoeba formerly called Nuclearia sp. ATCC50694, and we compare its morphological features with those of the genera Nuclearia and Fonticula. We also review the whole nucleariid lineage at the onset ofHolomycota, focusing on their diversity, ecology and evolutionary importance. SSU rRNA-based phylogenetic analyses including environmental sequences suggest that nucleariids are relatively scarce and thrive exclusively in freshwater systems. Based on existing transcriptomic data for Parvularia and novel data for a canonical Nuclearia strain, we carried out phylogenomic analyses to study the internal phylogeny of the whole group. Nucleariids occupy a key evolutionary position, such that mapping phenotypic traits on the phylogeny of Opisthokonts will help understanding important evolutionary transitions such multicellularity, parasitism or osmotrophy.
TESTATE AMOEBA IN BAU SEN AND BAU TRANG LAKES, BINH THUAN PROVINCE, VIETNAM
Tran Q.H., Nguyen T.H.T. Vietnamese-Russian Tropical Center [email protected]
The species composition and distribution of testate amoebae in Bau Sen and Bau Trang lakes (Binh Thuan Province, Vietnam) were investigated. Fifty-three species, varieties and forms have been
identified from the water column and sediments. Twenty-seven species, varieties and forms from the genera Arcella, Centropyxis, Cyclopyxis, Difflugia and Pyxidicula were found in Vietnam for the first time. The updated list oftestate amoebae in Vietnam now includes 286 taxa. The genera Arcella, Centropyxis and Difflugia are characterized by the highest frequency of occurrence. The species diversity of Arcella, Centropyxis, Difflugia was the highest. Centropyxis aculeata, Arcella discoides, Difflugia schurmanni, Netzelia oviformis and Difflugia limnetica were the most common species. Some taxa have shown restricted distribution, e.g. Lesquereusia modesta was found in Bau Trang lake with a high frequency of occurrence, but was not observed in Bau Sen lake. The number of observed species,varieties and forms in each lake is 34. The average number ofthe species per sample on the shores of the lakes subjected to human agricultural activity was significantly higher than in the samples from the shores of the lakes with less anthropogenic disturbance. The curves of "cumulative species number vs. sampling effort" are well fitted by equations S = 7.60N0-69 for Bau Sen lake and S = 12.52N0-46 for Bau Trang. The curves are unsaturated, which indicates that more intensive investigations oftestate amoebae should be expected to reveal more species.
DIVERSITY OF THE GENUS MONOCERCO-MONOIDES
Treitli S.C.1, Kotyk M.2, Yubuki N.1, Vlasakova J.1, Sramova E.1, Smejkalova P.1, Novotna K.K.1, Cepicka I.2, Hampl V.1
1 - Charles University in Prague, Faculty of Science, Department of Parasitology, Prague, Czech Republic
2 - Charles University in Prague, Faculty of Science, Department of Zoology, Prague, Czech Republic [email protected]
Monocercomonoides sp. is a genus of small flagellates belonging to the order Oxymonadida. They live as intestinal endosymbionts of insects, but some of them can be found also in the intestine ofvertebrates. In this work we sequenced the SSU rRNA of 35 different strains of Monocercomonoides isolated from various insect and vertebrate hosts and from unused cesspit. We have performed phylogenetic analysis in order to understand the diversity of this genus. Our preliminary results indicate large variation among strains at the genetic level with some strains having a typical 1800 bp SSU and some having around 3000 bp SSU sequence. The strains formed two clades, potentially distinct genera, however the position of these clades in the oxymonad trees is unclear and we have so far not found any good diagnostic feature discriminating
