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Heterolobosea is a group of mainly free-living amoebae, flagellates and amoeboflagellates closely related to Euglenozoa and Jakobida (supergroup Excavata). At least two heterolobosean lineages have reduced their mitochondria and live in low concentrations of oxygen (Psalteriomonadidae and extremely halophilic Pleurostomum). Moreover, some other presumably anaerobic species have been described in aerobic heteroloboseid genera, but their sequence data are still missing. The aim of this study is to recognize the diversity and phylogenetic position of both already described and novel non-hypersaline anaerobic heteroloboseans. We have isolated and cultivated 34 strains of free-living heterolobosean flagellates, amoebae and amoeboflagellates from freshwater, brackish and marine microoxic/anoxic habitats. 33 of these strains constitute a single clade (Psalteriomonadidae). We recognize 2 new genera and 3 new species. Phylogenetic analysis of SSU rDNA showed the genus Percolomonas is polyphyletic. The similar morphology of species formally placed within the genus Percolomonas is probably plesiomorphic. Finally, the marine strain PC4AM is morphologically unique and its morphology can not be compared with other heteroloboseans and eukaryotes. It is probably the most derived heterolobosean. Its cell structure...

Aquatic microbial food webs are in general size structured. Phytoplankton, which constitute the base of the food web, are grazed by protozoa and mesozooplankton, which in turn are consumed by planktivorous fish. Food web efficiency (FWE) is a measure of how efficiently energy is transported up the food web. FWE is low if the phytoplankton is inedible by the grazers, while FWE is higher if the phytoplankton community is dominated by edible phytoplankton. Recently, the presence of microfungi in aquatic food webs have been suggested to facilitate energy transfer up the food web, via the “mycoloop”. The aim of the study was to set-up a model system of phytoplankton – zooplankton food chains, relevant to the Baltic Sea, and to test FWE in diatom and flagellate-based food webs. Further, I wanted to introduce microfungi in the system and observe their impact on FWE. After many phytoplankton and zooplankton species tests, I decided to perform grazing experiments using one grazer, the ciliate Tetrahymena pyriformis, and two phytoplankton species: a diatom (Skeletonema marinoi) and a flagellate (Rhodomonas baltica). I hypothesized that T. pyriformis would more efficiently feed on flagellates than on diatoms. I performed a grazing experiment where the increase in ciliate abundance was measured, the consumption of the phytoplankton monitored and the FWE estimated. The diatom-based food web led to 14 times higher FWE than the flagellate-based food web. The variation in FWE may be explained by a difference in initial abundances introduced in the experimental treatment, which created unequal grazer:prey ratio between treatments. Further, the swimming behaviour of the flagellate might have reduced the capture efficiency by the ciliate. Microfungi were introduce in an experiment, from a natural seawater sample, but fungal infection was not observed for any of the tested phytoplankton species. Further development is needed to test the effects of microfungi on marine FWE.

A strain of Trichomonas vaginalis infected with a double-stranded RNA virus showed pronounced cytopathology in the form of giant syncytia generated by the recruitment of single cells. The giant cells ultimately lysed, releasing virus into the culture medium. In the infected cells, clusters of electron-dense particles resembling viral structures were found in the cytoplasm. In addition, distinctive inclusions composed of similar particles were present in the nuclei of some cells. Double-stranded viral RNA of 5.5 kbp was demonstrated in both cytoplasmic and nuclear fractions from these cells. Viral particles collected from the cell-free culture supernatant were of the same shape and size as the RNA virus isolated from a strain of T. vaginalis described previously (Wang and Wang, Journal of Biological Chemistry, 260: 3697-3702, 1985; Wang and Wang, Proceedings of the National Academy of Sciences of the U.S.A. 83: 7956-7986) which does not show this cytopathology.

The purpose of this study was to examine the direct and indirect effects of ultraviolet-B (UV-B) radiation on freshwater protists. Laboratory experiments were conducted in order to determine the importance of photoenzymatic repair (PER) of UVBinduced DNA damage in the heterotrophic nanoflagellate Paraphysomonas sp. Investigations into the combined effects of UV-B and chromophoric dissolved organic matter (CDOM) were conducted in laboratory experiments in which protist cultures were exposed to UV-B radiation in the presence and absence of water amended to a higher CDOM concentration in order to determine the ability of CDOM to act as a UV-B filter and as a potential nutrient source. Field experiments examined the responses of natural communities of protists and bacteria to ultraviolet radiation (UVR) in the presence of high and low concentrations of CDOM. Ultraviolet-B radiation (UV-B; 280 – 320 nm) negatively affects many aquatic organisms, including heterotrophic flagellates, by directly damaging DNA. The quantity of UV-B reaching the surface of a lake varies with atmospheric chemistry, including stratospheric ozone, and the presence of large holes (Alldredge 1977) in this ozone shield during the last decade resulted in historically high UV-B levels. In aquatic systems, the nature of the damage to organisms depends on the intensity and duration of solar radiation, plus its attenuation in the water column. The amount of UV-B damage is highly dependent on the concentration of CDOM in the water column because CDOM strongly absorbs UV-B radiation. This protective role of CDOM is likely to be reduced in areas where warmer, drier climate decreases watershed runoff, which ultimately results in acidification and increased CDOM photodegradation. However, CDOM also may also act as an organic carbon source for bacteria and stimulate growth of the microbial food web, including bacterivores like heterotrophic flagellates. The effect of UV and CDOM interactions on the microbial food web is not well understood, but climate-related increase in CDOM in an oligotrophic lake could increase the heterotrophic microbial food web impact by reducing UV-B damage and increasing available resources. Since aquatic organisms, including protists, are differentially susceptible to UV-B radiation, climate change effects on CDOM and UV-B attenuation are likely to alter the ecology and community structure of aquatic systems. This thesis describes investigations into the direct and indirect effects of UV-B radiation on freshwater protozoa. The role of PER of direct UV-B induced DNA damage was examined in laboratory experiments that compared the survival and population growth of the heterotrophic nanoflagellate Paraphysomonas sp. at two environmentally relevant temperatures. The results from these experiments demonstrated the reliance of Paraphysomonas sp. on PER, with 100% mortality in the absence of the photorepair radiation that activates photoenzymatic repair enzymes. The ability of Paraphysomonas sp. to recover from exposure to UV-B radiation declined in flagellates adapted to 15°C relative to the same exposures at 20°C. Experiments examining the direct and indirect effects of UV-B radiation and CDOM on freshwater protists conducted in the laboratory and in an oligotrophic lake in the Pocono Mountains showed that potential DNA damage resulting from UV exposure is reduced and microbial growth may be enhanced with an increase in CDOM concentration. / Biology

Made available in DSpace on 2016-02-26T14:53:08Z (GMT). No. of bitstreams: 1 ClaudiaBezerraSGoncalves.pdf: 706994 bytes, checksum: 7b1a77a7f4ff1c1b643ddf918c282667 (MD5) Previous issue date: 2007-02-28 / Most part of the external sensory receptaclles known are located in the antennal flagellate: sensilla placodea (olfactory discs, D.O.), basiconica, trichodea (cerdas), coeloconica, ampullaceae and campaniformia. The Apidae bees have been studied on diverse aspects, the external morphology, among which has call the attention for its importance is the bee antennae. The study of the antennae and their sensory olfactive structures has been done more frequently in highly social bees, such as Apina and Meliponina. The purpose of the paper was to analyze comparatively, at microscopic level, the size and the form of the antenna, the number and the distribution of the olfactory antennal structures or sensilla placodea in Euglossina and Meliponina bees with different social standards It was antennae from 10 males of Melipona favosa orbignyi and of Scaptotrigona depilis, 10 males of Eufriesea violaceae and of Exaerete smaragdina and 2 males of Exaerete dentata, totaling 62 bees analyzed for each species studied. For segment was counted the absolute number of the olfactory discs, it was measured diverse morphometric characters and obtained the following values AT (total area of the segment) aE (area with D.O), a (area with D.O.) and it was calculated the indices D.O./AT and D.O/aE. It was the Euglossina bees have more D.O., related to absolute numbers than the Meliponina. Among the Meliponina, the males and the workers the M. favosa orbignyi 5 have more absolute number of D.O., and comparing sex, the males have more D.O. than the females. As for the characters A (width of the segment) D and E (length of the segment), the Euglossina male show more value when compared to the workers and males of the Meliponina. As for the area of the antennal segment, Euglossina males present a total area AT much bigger than Meliponina. Among all the species analyzed, Euglossina show an area with olfactive structure (aE) and an area without theses D.O. (a) with similar sizes; while Meliponina, aE > a. Among the Meliponina, S. depilis have more discs (D.O./AT) with more concentration on the segment (D.O./aE) among the males, theses values are bigger than the females. The worker, M. favosa orbignyi, show theses indices much bigger than the males, indicating more quantity of D.O. with more concentration in the segment. Among all Euglossina, the males of Eufriesea violaceae have more D.O. than E. dentata and E. smaragdina (both with lower values than the Meliponina). Hence S. depilis, despite its smaller size, have the bigger number of D.O. than the Euglossina, Eufriesea violaceae have bigger number D.O. than the Exaerete (which are considered big bees and bigger than Eufriesea violaceae) / No flagelo antenal se encontra a maior parte de receptores sensoriais externos conhecidos: sensilla placodea (discos olfativos, D.O.), basiconica, trichodea (cerdas), coeloconica, ampullacea e campaniformia. Nas abelhas Apidae, têm sido estudadas sob os mais diversos aspectos, a morfologia externa, sendo que um dos caracteres que tem chamado a atenção pela sua importância é a antena das abelhas. O estudo das antenas e de suas estruturas sensoriais olfativas tem sido realizado com mais intensidade em abelhas altamente sociais, como nos Apina e Meliponina. O objetivo do trabalho foi analisar comparativamente, em nível de microscopia óptica, o tamanho e forma da antena, o número e a distribuição das estruturas olfativas antenais ou sensilla placodea em abelhas Euglossina e Meliponina com diferentes padrões sociais. Foram usadas antenas de 10 machos e 10 fêmeas de Melipona favosa orbignyi e de Scaptotrigona depilis; 10 machos de Eufriesea violaceae e de Exaerete smaragdina e, 2 machos de Exaerete dentata, totalizando 62 abelhas analisadas para cada espécie estudada. Para cada segmento foi contado o número absoluto de discos olfativos, foram medidos diversos caracteres morfométricos e obtidos os valores AT (área total do segmento), aE (área com D.O. ), a (área sem D.O.), e ainda, calculados os índices D.O./AT e D.O./aE. Verificou-se que as abelhas Euglossina têm mais D.O., em números absolutos, do que as Meliponina. Dentre os Meliponina, os machos e as operárias de M. favosa orbignyi tem maior número absoluto de D.O., e, na comparação entre os sexos, os machos possuem mais D.O. do que as fêmeas. 3 Referente aos caracteres A (largura total do segmento) D e E ( relativos ao comprimento do segmento), os maiores valores são apresentados pelos machos Euglossina, quando comparados com operárias e machos de Meliponina. Quanto às áreas do segmento antenal, os machos Euglossina apresentam a área total AT muito maior do que em Meliponina. Dentre todas as espécies analisadas, os Euglossina mostram a área com estruturas olfativas (aE ) e a área sem esses D.O.(a) com tamanhos semelhantes; enquanto que nos Meliponina, aE > a. Dentre os Meliponina, S. depilis têm mais discos (D.O./AT), com maior concentração no segmento (D.O./aE) sendo que nos machos, esses valores são maiores do que nas fêmeas. As operárias M. favosa orbignyi mostram esses índices bem maiores do que nos machos, indicando maior quantidade de D.O., com maior concentração no segmento. Dentre todos os Euglossina, os machos de Eufriesea violaceae têm mais D.O. do que E. dentata e E. smaragdina (ambos com valores inferiores aos dos Meliponina). Portanto S. depilis, independente de seu tamanho menor, têm o maior número de discos olfativos; e dentre os Euglossina, Eufriesea violaceae têm maior número de D.O. do que as Exaerete (que são consideradas abelhas de grande porte, e maiores que Eufriesea violaceae)