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Protistology ■ 11
University of Ostrava, 710 00 Ostrava, Czech Republic
2 - Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15Natsushima, Yokosuka, Kanagawa 237-0061, Japan
3 - Biology Centre, Institute of Parasitology, Czech Academy of Sciences, 370 05 Ceske Budejovice (Budweis), Czech Republic
4 - Faculty of Science, University of South Bohemia, 370 05 Ceske Budejovice (Budweis), Czech Republic
5 - A.A. Kharkevich Institute for Information Transmission Problems, Russian Academy ofSciences, 127 051 Moscow, Russian Federation
6 - Canadian Institute for Advanced Research, Toronto, Ontario M5G1Z8, Canada [email protected]
Diplonemea (Euglenozoa) is an understudied group of heterotrophic flagellates, related to euglenids and kinetoplastids. Diplonemids are abundant in the deep ocean and, surprisingly, represent the most diverse clade of pelagic eukaryotes, according to our metabarcoding data. There are four major clades within diplonemids: i/ clade of 'classic' diplonemids, Diplonema and Rhynchopus; ii/ small clade of Hemistasia; iii/ small clade of environmental sequences (DSPD II, deep-sea pelagic diplonemids II); iv/ large clade of environmental sequences (DSPD I). The DSPD I clade accounts for >97% of diplonemid abundance and diversity in the oceanic plankton, and Hemistasiaphaeocysticola, a recently isolated marine flagellate that feeds on diatoms and dinoflagellates, appears to be the closest relative of DSPD I according to some phylogenetic analyses. It not clear whether H. phaeocysticola is a predator, a parasite, or a scavenger of dead cells. An axenic culture was obtained from H. phaeocysticola growing with Thalassiosira cf. rotula. The genome and transcriptome of H. phaeocysticola were sequenced using 300 and 250 nt paired-end Illumina MiSeq reads, respectively. A draft genome assembly was obtained using CLC Genomics Workbench v.8.1 and has the length of ~260 Mbp and N50 of1.5 kbp. The results suggest that the genome of H. phaeocysticola is similar to that of Diplonema papillatum in size and has a very high repeat content. Additional genome sequencing using PacBio will be performed and the metabolism of H. phaeocysticola will be studied using a transcriptome assembly.
MIXOTROPHIC CILIATES AS SPECIAL ECOLOGICAL GROUP IN WATERBODIES OF CENTRAL AND LOWER VOLGA AND KAMA Bykova S.V.
Institute of ecology of the Volga river basin of RAS [email protected]
In plankton of polytypic waterbodies from Cent-
ral, Lower Volga and Kama 39 species of the mixotrophic ciliates are revealed. Their structure is heterogeneous: there are "epilimnic" aerophylic myxotrophs and microaerophylic or anaerobic myxotrophs. The first group appears in the low trophic state reservoirs; reservoirs with unstable stratification; in the epilimnium of the stratified waterbodies; in acid, colored, with level fluctuation waterbodies. The second group prefers microaerobic and anaerobic conditions of stratified eutrophic and hypertrophic lakes with high sulfides concentration. The absolute maximums of abundance (206540 ind./l) and biomass (7264 mg/m3) of mixotrophs are registered during summer stratification in a highly trophic meromictic pond, and the maximum contribution to biomass - in the small polyhumic lakes (98%).The ciliates' mixotrophic biomass (6,1 g/m3) is comparable with the anoxic phototrophic bacteria biomass (9,6 g/m3) and phytoflagellates (2,6 g / m3) in chemocline and adjacent layers. Their contribution to the overall "phototrophic" component biomass reaches about 37%, while in other waterbodies the total biomass of ciliates several orders of magnitude less than the biomass of other protists and bacteria. The scheme of different mixotrophs species confinement to various waterbodies and ecotopes in gradient of major abiotic factors has been drawn. An inverse relationship between environmental indicators saprobity and mixotrophic ciliates percentage was shown on example of oligo-mesotrophic lake. This can be used when assessing the state of aquatic ecosystems. It was proved that the species composition and the nature of their distribution are determined by specific abiotic and biotic conditions and weakly dependent on the zonal factors.
THE ROLE OF PROTISTS IN THE PLANKTON COMMUNITY OF FRESHWATER LAKE IN THE PERIOD OF ITS EUTROPHICATION Bykova S.V., Umanskaya M.V., Gorbunov M.U., Tarasova N.G., Zharikov V.V., Muchortova O.V. Institute of ecology of the Volga river basin of RAS [email protected]
The Lake Kandry-Kul is one of the largest natural lakes of the Middle Volga basin. It is a popular resting place and therefore experience significant recreation load. From 2010 to 2012 the trophic level ofthe lake has increased from a predominantly oligotrophic to mesotrophic. We studied the following groups ofprotists: ciliates, dinoflagellates, chrysophytes, cryptophytes and euglenids. Their biomass in 2012 compared to 2010 has increased 2.4 times. Their contribution to the total biomass of plankton community and to the to-tal unicellular
