• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 143
  • 96
  • 13
  • 9
  • 7
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 2
  • 2
  • 1
  • Tagged with
  • 318
  • 110
  • 66
  • 32
  • 29
  • 29
  • 27
  • 23
  • 22
  • 21
  • 20
  • 19
  • 17
  • 16
  • 16
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

The Blood-brain barrier in normal and pathological conditions / by Chunni Zhu.

Zhu, Chunni January 2001 (has links)
Bibliography: leaves 318-367. / x, 367 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the blood-brain barrier in normal and pathological conditions induced by intravascular and extravascular insults. Intravascular insults were induced by administration of Clostridium perfringens prototoxin; extravascular insults were induced by an impact acceleration model for closed head injury to induce traumatic brain injury. Also examines the integrity of the blood-brain barrier ultrastructurally and by its ability to exclude endogenous and exogenous tracers. Also studies the expression of 2 blood-brain barrier specific proteins, endothelial barrier antigen (EBA) and glucose transporter 1 (GLUT1) / Thesis (Ph.D.)--University of Adelaide, Dept. of Anatomical Sciences, 2002?
142

A study of intra-ring checking and xylogenesis in Pinus radiata D.Don

Nair, Hema January 2006 (has links)
Pinus radiata is the dominant species of the plantations forests in New Zealand. The forest industry in New Zealand is heavily dependant on it. However, Pinus radiata can develop wood quality flaw called 'intra-ring checking'. The checks or splits appear in wood during kiln drying and usually affect the earlywood region of the wood. It lowers value of appearance grade timber leading to huge economic loses for the forest industry. This thesis presents a study that was undertaken as a part of ongoing collaborative work that is being carried out to understand wood quality issues in Pinus radiata, with a vision of improving its wood quality. This study was a part of that effort and was conducted with an aim to gain an insight into intra-ring checking, and the process of xylogenesis in Pinus radiata. The investigations for this study were carried out in two steps. The first step was to understand intra-ring checking. The location of intra-ring checking was determined by observing the checks using various microscopy techniques. Scanning electron microscopy confirmed that checking was as an intercell failure that usually occurs at the cm1/S1 boundary. A comparative study was also conducted to see if the checked wood had some inherent properties that made it more susceptible to checking. It was found that checking could be influenced by tracheid geometry and cell wall thickness. If the wood had large tracheids with thin walls, it was more likely to develop checks during drying. Lignin distribution in the cell wall layers was also seen to play an important role in checking. Lower lignin levels and disruption in the pattern of lignification of the cell wall layers increased the tendency of the wood to develop checks. Similarly, it the tracheids have larger pits then their tendency to check increases. Structural features that disrupt the uniformity of the interlocking pattern of the tracheid such as rays and resin canals could also play a role in checking. Checked wood tends to have more surface area occupied by ray tissue. However, resin canals do not seem to be directly involved in checking, though their arrangement could indicate disturbances during xylogenesis. The second step was to understand the process of xylogenesis in Pinus radiata especially with respect to the influence of auxin and boron on it. Nutrient and organ culture methods were manipulated and successfully used to study xylogenesis. An exhaustive comparative study was carried out to observe and measure selected wood properties. Microscopy and image analysis revealed that auxin and boron changes in the medium led to the alterations in the cell division, expansion and lignification. However, the analysis of the measurements and the observations displayed complex 'between-tree' and 'within-culture variations'. Clear trends did not emerge from the analysis hence, a confident conclusion on the association between auxin, boron and lignification could not be drawn from this organ culture study. The study has added to the knowledge about checking and wood properties associated with it. A new tool of organ culture had been established that can hlep future research on the process of xylogenesis in Pinus radiata.
143

Mechanisms regulating the thermal acclimation of dark respiration in snow tussock and ryegrass

Clifford, Veronica Rose January 2007 (has links)
The aim of this research was to identify the mechanisms that underpin changes in respiratory capacity during acclimation to temperature. Dark respiration, enzyme activities and leaf ultrastructure were measured from ryegrass (Lolium perenne) in controlled environmental chambers and two species of native grass (Chionochloa rubra & C. pallens) growing at different altitudinal ranges on Mount Hutt, Canterbury, New Zealand. The overall hypothesis was that the changes in both mitochondrial numbers and enzyme activity underpin the greater respiratory capacity observed in response to decreasing temperatures. Gas exchange measurements were carried out to measure rates of dark respiration (Rd) in leaves of both ryegrass and tussocks. Respiratory homeostasis (full acclimation) was achieved in ryegrass leaves but only partial acclimation in both species of tussock plants. Dark respiration rates for warm-grown ryegrass were greatly reduced compared to cool-grown grasses. Rd was lower for C. rubra growing at the base of the mountain (450m) compared to plants at a higher altitude (1060m). The dark respiration rates were also lower for C. pallens growing at 1070m than at 1600m. When comparing Rd between high and low altitude plants, it was significantly lower in low altitude plants at 450m than at 1600m. Oxygen consumption was measured in intact leaves and roots, crude mitochondria and isolated mitochondria from ryegrass to investigate whether a change in respiratory capacity was involved with changes in Rd. Mitochondrial respiratory capacity was slightly reduced in warm leaves and roots (not significantly). The respiratory capacity results from isolated mitochondria for C. rubra (at 450m and 1060m) and C. pallens (at 1070m and 1600m) were consistent with the hypothesis that plants from warm sites have lower respiratory capacity in comparison to plants from cool sites. Based on these results and those of previous studies, it was concluded that respiratory flux for any given temperature is not simply determined by maximal capacities of the respiratory apparatus but rather a combination of the availability of substrate supply, the demand for respiratory products (i.e. ATP) and/or the maximal capacity of respiratory enzymes. Utilizing transmission electron micrographs, it was found that mitochondria were significantly less abundant in warm-grown than cool-grown ryegrass mesophyll cells. Mitochondria dimensions increased slightly between the cool and warm treatment. At lower altitudes (C. rubra), there was a significant decrease in mitochondria numbers with decreasing elevation. At higher altitudes (C. pallens), there was no noticeable change in mitochondria numbers between 1070m and 1600m. It was concluded that mitochondrial abundance for the controlled and field experiments, and mitochondrial sizes in the field, were associated with changes in Rd. The maximal activities of fumarase and succinate dehydrogenase (SDH) in isolated mitochondria from leaves of ryegrass and tussock were measured spectrophotometrically. The results in the controlled experiment indicate that enzymes other than fumarase and SDH could be responsible for the increased respiratory capacity observed in cold acclimated leaves of ryegrass. However, fumarase maximal activity was significantly reduced in C. rubra at low altitude compared with C. pallens growing at high altitude - this suggests that it may be involved in the differences in respiratory capacity and Rd between the two sites. Succinate dehydrogenase did not differ significantly in response to altitude. The large difference between the two field sites for fumarase activity is comparable to the large difference in Rd and reduction in mitochondrial abundance and dimensions seen between the two sites. This supports the overall hypothesis that cool-grown plants keep up with energy demands at low temperatures by increasing enzyme concentrations/capacity. The results of this study are supportive of the hypothesis that growth in low altitudes and warm conditions will result in the reduction of Rd as a consequence of: (1) temperature sensitivity of the respiratory apparatus, resulting in the reduction of the respiratory capacities of mitochondria; (2) a reduction in mitochondria size and numbers; and as a consequence of this (3) a reduction in the activities of mitochondrial enzymes. However, these responses are species specific and vary according to the range of temperatures experienced by plants in the field and controlled environments.
144

An ultrastructural study of the symbiotic relationships of four strains of Bradyrhizobium japonicum with glycine max /

Huber, Mary Christine, January 1997 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 456-600). Also available on the Internet.
145

An ultrastructural study of the symbiotic relationships of four strains of Bradyrhizobium japonicum with glycine max

Huber, Mary Christine, January 1997 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 456-600). Also available on the Internet.
146

Development, degeneration and regeneration of nerve fibres in the feline inferior alveolar nerve and mandibular incisor pulps light and electron microscopic studies /

Fried, Kaj. January 1982 (has links)
Thesis (doctoral)--Karolinska Institutet, Stockholm, 1982. / Extra t.p. with thesis statement inserted. Includes bibliographical references (p. 20-28).
147

Development, degeneration and regeneration of nerve fibres in the feline inferior alveolar nerve and mandibular incisor pulps light and electron microscopic studies /

Fried, Kaj. January 1982 (has links)
Thesis (doctoral)--Karolinska Institutet, Stockholm, 1982. / Extra t.p. with thesis statement inserted. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. 20-28).
148

Efeitos da rosuvastatina e da atividade física de baixa intensidade na morfologia renal de ratos normotensos e espontaneamente hipertensos (SHR) / Effects of the rosuvastatin and low intensity physical activity on the morphology of kidney from normotensive and spontaneously hypertensive rats (SHR)

Angelica Beatriz Garcia Pinto 30 September 2011 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Desordens do sistema renal podem ser as causas da hipertensão arterial, a qual pode, por sua vez, causar doenças renais. A pressão sanguínea elevada é muito comum também nas doenças crônicas dos rins, e é, além disso, um conhecido fator de risco para uma mais rápida progressão da falha renal. A incidência de doenças renais crônicas está aumentando no mundo, e há uma grande necessidade de identificar as terapias capazes de deter ou reduzir a progressão da doença. Há crescente evidência de que as estatinas poderiam desempenhar um papel terapêutico. Além disso, tem sido demonstrado que a atividade física melhora a função renal em pacientes. Estudos ultra-estruturais em humanos e em ratos demonstraram a presença de junções gap dentro de todas as células do glomérulo e os podócitos demonstraram conter principalmente conexina-43 (Cx-43). O presente estudo tem como objetivo observar os efeitos da rosuvastatina e da atividade física de baixa intensidade na estrutura e ultra-estrutura renal e na expressão glomerular de Cx-43 em ratos normotensos (WKY) e em ratos espontaneamente hipertensos (SHR). Os ratos foram divididos aleatoriamente em oito grupos: WKY-C: animais normotensos que não receberam rosuvastatina; WKY-ROS: animais normotensos que receberam rosuvastatina 20mg/kg/dia por gavagem orogástrica; SHR-C: animais hipertensos que não receberam rosuvastatina; SHR-ROS: animais hipertensos que receberam rosuvastatina, como descrito no grupo WKY-ROS; SED-WKY: animais normotensos sedentários; EX-WKY: animais normotensos exercitados; SED-SHR: animais hipertensos sedentários; e, EX-SHR: animais hipertensos exercitados. Os animais dos grupos SHR-C, SHR-ROS e SED-SHR apresentaram níveis de pressão arterial maiores que os animais dos grupos WKY-C, WKY-ROS, SED-WKY, EX-WKY e EX-SHR. A massa corporal dos grupos de animais não diferiram significativamente durante o experimento. Não houve diferença nos níveis sanguíneos de uréia, creatinina, ácido úrico e creatinafosfoquinase entre os animas dos grupos estudados. No entanto, houve um aumento da excreção de proteína de 24 horas nos animais do grupo SHR-C. Houve um aumento na área capsular nos animais do grupo SHR-C. Por microscopia eletrônica de transmissão observou-se que nos animais SHR-C e SED-SHR a barreira de filtração glomerular, o diafragma de fenda e os podócitos estão alterados exibindo os vacúolos nos podócitos e pedicelos mais curtos e mais espessos. Por microscopia eletrônica de varredura, os animais SHR-C e SED-SHR exibiram pedicelos mais afilados, curtos e tortuosos. Um aumento da imunofluorescência para Cx-43 foi observada em células epiteliais viscerais dos glomérulos dos animais do grupo WKY-ROS e nas células parietais e viscerais dos glomérulos dos animais do grupo SHR-ROS, se comparado com os grupos WKY-C e SHR-C. Por outro lado, os animais dos grupos SED-SHR e EX-SHR exibiram diminuição da expressão de Cx-43, comparados aos animais SED-WKY e EX-WKY. Em conclusão, podemos supor que os efeitos renais da rosuvastatina e da atividade física de baixa intensidade podem ser ferramentas terapêuticas para melhorar a estrutura e conseqüentemente a função renal em indivíduos hipertensos / Disorders of the renal system may be the cause of hypertension, which can in turn cause kidney disease. The high blood pressure is also very common in chronic kidney diseases, and is also a known risk factor for faster progression of renal failure. The incidence of chronic kidney disease is increasing worldwide, and there is a great need to identify therapies to stop or slow the progression of the disease. There is growing evidence that statins could play a therapeutic role. Moreover, it has been shown that physical activity improves renal function in patients. Ultrastructural studies in humans and rats have shown the presence of gap junctions in all cells of the glomerular podocytes and also to contain mainly connexin-43 (Cx-43). This study aims to observe the effects of rosuvastatin and low-intensity physical activity on the structure and ultrastructure of kidney and glomerular expression of Cx-43 in normotensive rats (WKY) and spontaneously hypertensive rats (SHR). The rats were randomly divided into eight groups: WKY-C: normotensive animals not receiving rosuvastatin, WKY-ROS: normotensive animals that received rosuvastatin 20mg/kg/day by orogastric gavage, C-SHR: hypertensive animals not receiving rosuvastatin; SHR -ROS: hypertensive rats that received rosuvastatin, as described in ROS-WKY group, WKY-SED: sedentary normotensive, WKY-EX: normotensive rats exercised, SHR-SED: sedentary hypertensive rats, and EX-SHR: hypertensive rats exercised . The animals in groups C-SHR, SHR-SED and SHR-ROS had blood pressure levels higher than the animals in groups WKY-C, ROS-WKY, WKY-SED, EX-SHR and EX-WKY. The body mass of groups of animals did not differ significantly during the experiment. There was no difference in urea, creatinine, uric acid and creatine phosphokinase blood levels among animals of the studied groups. However, there was an increased excretion of 24 hours protein in SHR-C group. There was an increase in the capsule in group SHR-C. Transmission electron microscopy showed that in SHR-C and SED-SHR glomerular filtration barrier, the slit diaphragm and podocyte were altered. By scanning electron microscopy, the C-SHR and SED-SHR animals exhibited thinner, shorter and more tortuous pedicels. An increase in immunofluorescence for Cx-43 was observed in visceral epithelial cells of the glomeruli of group and in WKY-ROS and in visceral and parietal cells of the glomeruli of SHR-ROS group, compared with WKY-C and SHR- C. On the other hand, SHR-SED and EX-SHR animals exhibited decreased expression of Cx-43 compared with WKY-SED and EX-WKY animals. In conclusion, we can assume that the renal effects of rosuvastatin and low-intensity physical activity can be therapeutic tools to improve the structure and consequently renal function in hypertensive subjects
149

Avaliação dos impactos gerados pela vinhaça bruta e após ajuste de pH, em representantes da fauna edáfica / Evaluation of the impacts generated by raw vinasse and after adjustment of pH, in representatives of edaphic fauna

Moreira-de-Sousa, Cristina 28 September 2018 (has links)
Submitted by Cristina Moreira de Sousa (cris.sousa.bio@hotmail.com) on 2018-11-16T19:09:39Z No. of bitstreams: 1 TESE_FINAL.pdf: 12822240 bytes, checksum: 95a68963a7d69ea36b5f1c6e387b657e (MD5) / Approved for entry into archive by Ana Paula Santulo Custódio de Medeiros null (asantulo@rc.unesp.br) on 2018-11-21T12:04:39Z (GMT) No. of bitstreams: 1 sousa_cm_dr_rcla.pdf: 12288951 bytes, checksum: cc35b50df2f7b0c64472eb843e2439ea (MD5) / Made available in DSpace on 2018-11-21T12:04:39Z (GMT). No. of bitstreams: 1 sousa_cm_dr_rcla.pdf: 12288951 bytes, checksum: cc35b50df2f7b0c64472eb843e2439ea (MD5) Previous issue date: 2018-09-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A cana-de-açúcar é uma das principais culturas mundialmente difundida e a alta produtividade resulta na geração de inúmeros resíduos. A vinhaça, resíduo da produção do etanol tem chamado a atenção devido suas características e propriedades, quando empregada na fertirrigação das culturas de cana-de-açúcar. Diversos benefícios foram descritos, ganhos na fertilização e enriquecimento do solo, bem como aumentos na produtividade. Entretanto, a vinhaça também apresenta substâncias que podem ser nocivas, afetando negativamente a fauna existente nos locais de aplicação do resíduo. Frente a essa problemática, diversos estudos foram desenvolvidos com o intuito de melhor compreender os impactos da vinhaça no meio ambiente e, mesmo diante dos benefícios que a fertirrigação com a vinhaça implica economicamente ainda há a necessidade de maiores cuidados com a utilização do resíduo no campo. Nesse contexto, o objetivo deste trabalho foi propor um tratamento para a vinhaça, ajustando seu pH em 7,0 (neutro) utilizando cal (CaO), com a intenção de amenizar sua toxicidade para posterior uso no solo, visto que, um dos grandes problemas apresentados pela vinhaça é o pH ácido. O uso de cal foi escolhido por ser este produto utilizado em campo para correção do solo. Foi associado o uso de diversos biomarcadores à bioindicadores de solo, além de testes ecotoxicológicos para avaliar o efeito da vinhaça bruta em comparação à vinhaça tratada. Diplópodos da espécie Rhinocricus padbergi foram expostos à vinhaça em sua forma bruta e tratada com CaO, na concentração estabelecida pela Norma da CETESB, e ao dobro desta mesma concentração, simulando uma situação de super dosagem. A análise do intestino médio destes animais por meio das ferramentas ultraestruturais, imunohistoquímica e marcação de morte celular revelou que a vinhaça bruta pode ocasionar danos nos tecidos dos animais expostos e que o tratamento desta vinhaça surtiu efeito na diminuição desses danos. Testes ecotoxicológicos de fuga e reprodução, padronizados mundialmente pela Organização Internacional de Normalização (ISO), foram realizados com as espécies Eisenia andrei, Enchytraeus crypticus e Folsomia candida; de um modo geral, observou-se que as espécies E. crypticus e F. candida não tiveram seus comportamentos influenciados pela vinhaça bruta e nem pela vinhaça tratada, mas a espécie E. andrei apresentou-se mais sensível a presença da vinhaça no solo demonstrando comportamento de fuga em concentrações mais elevadas de vinhaça bruta e tratada, e, no teste de reprodução, respondeu a exposição à vinhaça tratada, com aumento no número de juvenis em relação a vinhaça bruta. Logo, o emprego da vinhaça na fertirrigação ainda requer cuidados, uma vez que seus efeitos nocivos são notórios, e nesse sentido, a alternativa de neutralizar seu pH pode representar uma medida de emprego desse resíduo com menos impacto. / Sugarcane is one of the main crops worldwide and the high productivity results in the generation of many wastes. Vinasse, the residue of ethanol production, has attracted attention because of its characteristics and properties, when used in the fertirrigation of sugarcane crops. Several benefits have been described, gains in fertilization and soil enrichment, as well as increases in productivity. However, the vinasse also presents substances that can be harmful, negatively affecting the fauna existing in the places of application of the residue. Faced with this problem, several studies were developed with the purpose of better understanding the impacts of vinasse in the environment and, even in view of the benefits that fertirrigation with vinasse implies economically, there is still a need for greater care with the use of the residue in the field. In this context, the objective of this work was to propose a treatment for vinasse, adjusting its pH to 7.0 (neutral) using lime (CaO), with the intention of mitigating its toxicity for later use in the soil, since one of the great problems presented by vinasse is acid pH. The use of lime was chosen because this product is used in field for soil correction. It was associated the use of several biomarkers to soil bioindicators, as well as ecotoxicological tests to evaluate the effect of raw vinasse in comparison to the treated vinasse. Diplopods of the species Rhinocricus padbergi were exposed to vinasse in their raw form and treated with CaO, at the concentration established by the CETESB Standard, and at twice the same concentration, simulating a super dosage situation. The analysis of the midgut of these animals using ultrastructural tools, immunohistochemistry and cell death marking revealed that raw vinasse can cause damage to the tissues of the exposed animals and that the treatment of this vinasse had an effect in reducing these damages. Ecotoxicological tests of the avoidance and reproduction tests, standardized worldwide by the International Organization for Standardization (ISO), were carried out with the species Eisenia andrei, Enchytraeus crypticus and Folsomia candida; in general, E. crypticus and F. candida were not influenced by raw vinasse or treated vinasse, but the E. andrei species was more sensitive to the presence of vinasse in the soil, demonstrating in the higher concentrations of raw and treated vinasse, and in the reproduction test, the exposure to treated vinasse responded, with an increase in the number of juveniles in relation to raw vinasse. Therefore, the use of vinasse in fertigation still requires care, since its harmful effects are notorious, and in this sense, the alternative of neutralizing its pH can represent a measure of the use of this residue with less impact. / CAPES: 001
150

Taxonomia e distribuiçao do gênero Aulacoseira Thwaites(Bacillariophyta ) no Brasil

Tremarin, Priscila Izabel January 2012 (has links)
O gênero Aulacoseira Thwaites é exclusivo de águas continentais e possui ampla distribuição mundial. As espécies do gênero vêm sendo estudadas, principalmente para regiões temperadas da América do Norte e Europa. Atualmente, Aulacoseira conta com aproximadamente 60 espécies, dentre fósseis e atuais. No Brasil, apenas 17 espécies foram registradas e poucos trabalhos apresentaram informações sobre a ultra-estrutura da frústula. Desta forma, o presente estudo teve por objetivos analisar as características morfológicas e estruturais das espécies de Aulacoseira do Brasil e a distribuição geográfica das espécies em ambientes aquáticos brasileiros. O estudo baseou-se em 286 amostras de plâncton e perifíton, procedentes de diversos tipos de ambientes, como rios, lagos, lagoas e reservatórios, abrangendo 24 estados brasileiros. Exemplares de Aulacoseira foram analisados sob microscopia óptica e eletrônica de varredura e transmissão. Os táxons encontrados foram descritos, mensurados, ilustrados e comentados. Uma chave dicotômica foi providenciada para auxiliar na determinação das espécies e glossário para compreensão das estruturas. A análise do material permitiu a identificação de 23 táxons infragenéricos de Aulacoseira, sendo 18 espécies, três variedades não típicas e duas formas taxonômicas. Dentre estas, seis constituíram novas espécies para ciência (A. brasiliensis, A. calypsi, A. minuscula, A. pantanalensis, A. samariana e A. simoniae) e duas não foram determinadas em nível específico. Aulacoseira pseudoamericana e A. herzogii var. minor constituíram citação pioneira para o Brasil e A. gessneri teve sua ultra-estrutura documentada pela primeira vez. Dos 29 táxons infragenéricos de Aulacoseira já registrados para o Brasil, apenas 13 foram encontrados durante o estudo, alguns táxons foram reidentificados e outros puderam ser revistos devido há ausência de informações complementares nas publicações. Aulacoseira calypsi, A. gessneri, A. pantanalensis, A. pseudoamericana, A. samariana e A. herzogii var. minor apresentaram distribuição restrita à áreas de clima tropical enquanto que Aulacoseira cf. alpigena, A. granulata var. angustissima f. spiralis e Aulacoseira sp.2 ocorreram exclusivamente em regiões subtropicais. O elevado número de novas espécies encontradas ressalta a importância de estudos taxonômicos mais aprofundados para melhor conhecimento das características diacríticas das espécies que ocorrem em ambientes continentais brasileiros. Palavras-chave: ambientes continentais, diatomáceas cêntricas, taxonomia, ultra-estrutura. / The genus Aulacoseira Thwaites is exclusive of continental waters and has worldwide distribution. The species of this genus have been widely studied, mainly to temperate regions of North America and Europe, and the taxa that occur in South America are poorly known. Currently, Aulacoseira has approximately 60 species, among fossil and recent. In Brazil, only 17 species were recorded and few studies presents data on the ultrastructure of the frustule. Thus, this study aimed to analyze the structural and morphological features of the Aulacoseira genus and geographical distribution of species in aquatic environments in Brazil. The study was based on 286 samples of plankton and periphyton, collected in different types of environments such as rivers, lakes, ponds and reservoirs distributed in 24 states. Specimens of Aulacoseira were examined under light and electron microscopy. The taxa were described, measured, illustrated and discussed. Dichotomous key was provided to assist in determining the species and glossary for understanding the structures described. The analysis allowed the identification of 23 infrageneric taxa of Aulacoseira, with 18 species, three varieties and two non typical taxonomic forms. Among these, six new species for science were found (A. brasiliensis, A. calypsi, A. minuscula, A. pantanalensis, A. samariana e A. simoniae) and two were not determined at specific level. Aulacoseira pseudoamericana and A. herzogii var. minor were first recorded in Brazil and A. gessneri its ultrastructure was first revealed. Of the 29 taxa of Aulacoseira already recorded in Brazil, only 13 were found during the study, some taxa were reidentified and others could not be revised because there is no additional information in publications. Aulacoseira calypsi, A. gessneri, A. pantanalensis, A. pseudoamericana, A. samariana and A. herzogii var. minor present distribution restricted to tropical areas while Aulacoseira cf. alpigena, A. granulata var. angustissima f. spiralis and Aulacoseira sp.2 occurred exclusively in the subtropics.The high number of new species found highlights the importance of more detailed taxonomic studies to improve knowledge of diacritical features of the species occurring in Brazilian environments.

Page generated in 0.0602 seconds