CC BY
22
50 • "PROTIST—2016
strain) and marine waters (two strains) has been considered. The morphology of these strains is relatively similar. The anterior flagellum lies inside the hollow proboscis. The posterior flagellum goes along the ventral groove. Two heterodynamic flagella are smooth and have not been covered by any structures. The transitional zone of the flagella do not contain additional elements and are ofthe usual structure. The microtubule band and anterior rootlet are inserted from the kinetosome of the anterior flagellum, the microtubule right and left rootlets and single rootlet are inserted from the kinetosome of the posterior flagellum. The kinerosomes are located at obtuse angle or antiparallel and connected by the three fibrils and cross-striated structure. The rhizoplast has not been found. The thickened cell coverings consist of plasmalemma and epiplasm. The margins of the coverings form the folds, the ventral groove goes between them and is bounded only by the plasmalemma. The vesicular nucleus and Golgi apparatus are of the usual structure. The mitochondria contain tubular cristae. The pseudopodia inserting from ventral groove serve to capture bacteria. Front cytoplasmic outgrowth have been found for the first time. The resemblance and differences ofgiven species with other apusomonads have been shown. This study was supported by the Russian Foundation for Basic Research (grant nos. 14-04-00500, 14-04-00554, 15-29-02518).
THE ULTRASTRUCTURE OF AMOEBOID FLAGELLATE THAUMATOMONAS COLO-NIENSIS WYLEZICH ET AL. 2007 (CERCO-ZOA, RHIZARIA) Mylnikov A.P., Prokina K.I. Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia ap.mylnikov@rambler.ru
The ultrathin structure of amoeboid flagellate Th. coloniensis has been considered. The cell is surrounded by somatic scales which forming on the surface of the mitochondria. The heterodynamic flagella emerge from the small flagellar pocket. Both flagella are covered by the cone—shaped scales and thin twisted mastigonemes. The kinetosomes lie parallel to each other. The transitional zone of the flagella contains the thin—walled cylinder. The transversal plate of the flagella is located above cell surface. The flagellar root system consists of 3 microtubular bands and fibrillar rhizoplast. The vesicular nucleus and Golgi apparatus are of the usual structure. The mitochondria contain the tubular cristae. The extrusive organelles (kineto-cysts) which contain the amorphous material and capsule have been found in cytoplasm. The capsule
consists of the muff and cylinder. Osmiophilic bodies of various shapes contain crystalloid inclusions. The pseudopodia capturing the bacteria are inserted ventrally. The groove is armored by the two longitudinal groups of closely situated microtubules. Microbodies and symbiotic bacteria have not been observed. Th. coloniensis differs from other Thaumatomonas species by the presence of osmiophlic bodies and absence ofmicrobodies. This study was supported by the Russian Foundation for Basic Research (grant nos. 14-04-00500, 14-0400554,15-29-02518).
PLANKTONIC CILIATES OF THE SHEKSNA
RESERVOIR
Mylnikova Z.M.
Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia m.mylnikova@rambler.ru
The species composition, abundance, biomass and distribution of planktonic ciliates across the Sheksna Reservoir consisting of three parts have been studied. Fifteen species of ciliates, belonging to four classes: Spirotrichea - 6, Litostomatea - 4, Prostomatea - 4, Oligohymenophorea - 1 were recorded during the observation period in the pelagic zone. The maximal number of species (11) was registered in Beloye Lake, minimal one (6) - in Kovzhinsk part. The following species: Tintinnidium fluviatile, Codonella cratera, Limnostrombidium viride, L. pelagica and Rimostrombidium velox were dominants in the most part of sampling points. Paradileptus conicus, Monodinium balbiani, Enchelis pupa and Prorodon ovum were registered less frequently and in small quantities , and has been recorded for the first time on this site. The maximal average abundance (2502 * 103 ind./m3) and biomass (141 mg/m3) were registered in Beloye Lake. The maximal density (27 50-4 150 * 103 ind./ m3 and 156-352 mg/m3) observed in shallow waters of the western coast, in sampling points Mandoma, Kustovo, Kium-Mandoma and Belozersk. Lower density (1150-1250 * 103 ind./m3 and 62-90 mg/ m3) observed in sampling points near the center of the lake, and Sudovoy Khod station. The average values of abundance and biomass of Sheksna Reservoir accounted 1875000 ind./m3 and 123 mg/ m3, respectively. The trophic status of the Sheksna Reservoir during the study period can be described as mesosaprobic.
PUF PROTEINS IN GIARDIAINTESTINALIS Najdrova V., Dolezal P.
Department of Parasitology, Faculty of Science, Charles University in Prague, Prague, Czech Republic
Protistology ■ 51
najdrova.vladimira@seznam.cz Giardia intestinalis, an anaerobic protozoan parasite, contains highly compact genome with extremely short untranslated regions (UTRs). The regulation ofgene expression during giardia cell- and life-cycle has been poorly studied and only a handful of RNA binding proteins have been characterized so far. PUF proteins bind 3' UTRs of cognate mRNAs, by which they regulate their stability, translation and localization. These eukaryotic proteins are evolutionarily conserved from protists to metazoans. We have identified five PUF genes in the genome of G. intestinalis and have initiated studies towards the characterization of PUFs in giardia biology.
EXPLORING CELL TYPE DIFFERENTIATION IN THE FILASTEREAN CAPSASPORA OWCZARZAKI BY SINGLE-CELL RNA-SEQ Najle S.R.1, Florenza J.1, Mazutis L.2, Ruiz-Trillo
I 1,3,4
1 - Institut de Biologia Evolutiva (Univesitat Pompeu Fabra — CSIC). Pg. Maritim de la Barceloneta 37-49, 08003, Barcelona, Catalonia, Spain
2 - Institute ofBiotechnology, Vilnius University. V.A. Graiciuno 8, LT-02241, Vilnius, Lithuania
3 - Departament de Genutica, Universitat de Barcelona, Av. Diagonal, 645, Barcelona 08028, Catalonia, Spain
4 - Instituciy Catalana de Recerca i Estudis Avangats (ICREA), Passeig Lluis Companys, 23, Barcelona 08010, Catalonia, Spain. sebastian.najle@upf.edu
The origin of multicellular animals from their unicellular ancestors is one of the most important evolutionary transitions in life's history. However, the specific cellular and genetic changes that led to this transition remain unknown. Phylogenomic analyses have shown that animals are closely related to three unicellular lineages: choanoflagellates, filastereans and ichthyosporeans, altogether forming the Holozoa clade. Recent phylogenomic studies have shown that those premetazoan taxa already had a complex repertoire of genes important for multicellularity, some of them previously thought to be exclusive of animals. Different versions of "simple multicellularity" are found among the unicellular relatives of Metazoa. There is the clonal development of colonial choanoflagellates, the aggregative behavior of Capsaspora owczarzaki, and the coenocytic development of ichthyosporeans. Those colonies and aggregates are assumed to be without cell differentiation. However, there is no molecular data proving that all cells within those colonies or aggregates or coenocytes are identical. Here we show microscopic evidence for the coexis-
tence of different cell types in C. owczarzaki aggregates. We also show our advances in developing single-cell transcriptomics methodology in these organism to molecularly characterize cell types. The possibility of analyzing differential gene expression at the single-cell level between diverse cell types of unicellular holozoans will allow us to better understand the molecular mechanisms underlying programs of cell differentiation in the origin of animals. The aggregates of C. owczarzaki offer us an ideal model in which to test this, and provide a better framework to understand the origin of the different metazoan cell types.
PHYLOGENY AND ECOLOGICAL IMPORTANCE OF PHAEODARIANS (CERCOZOA, RHIZARIA)
Nakamura Y.1, Somiya R.2, Suzuki N.3, Hori S. R.4, Tuji A.1
1 - Department ofBotany, National Museum ofNature and Science
2 - Graduate School of Fisheries Science and Environmental Studies, Nagasaki University
3 - Graduate School ofScience, Tohoku University
4 - Graduate School ofScience and Engineering, Ehime University
y.nakamura@fish.hokudai.ac.jp Phaeodarians are a group of marine protists belonging to the phylum Cercozoa, composing Rhizaria (SAR). These unicellular siliceous zooplankton occasionally become abundant in the ocean, however their ecological importance and phylogeny are still wrapped in mystery. Plankton were sampled from several depths at ca. 40 stations in the Northern hemisphere during 2011—2015. Zooplankton were sorted and identified in order to clarify the species composition of each sample. Some phaeodarians were cultured to observe their behavior. The 18S rDNA sequences of phaeodarians were determined by single-cell PCR method. Two undescribed phaeodarians were found in the deep waters in the Sea of Japan, and one of the species was abundant through the year, occupying ca. 22% of the total zooplankton biomass on average. The abundance of phaeodarians was also seen in the East China Sea, where two species occupied 10.2—13.9% of the zooplankton biomass, suggesting that this group is an important component of the zooplankton community and the material cycle in the ocean. The cell division ofphaeodarians was observed during the culture experiment. The species morphologically identified as phaeodarians formed a single clade together with other cercozoans in the phylogenetic tree, suggesting that almost all phaeodarians belong to Cercozoa and that Phaeodaria is a monophyletic
