Taxonomia e distribuição do gênero Navicula "sensu stricto" (Bacillariophyceae) em reservatórios da Bacia do Alto Tietê e de bacias vizinhas
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Data
2016-08-04
Autores
Dávila, Jennifer Paola Moyón [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O gênero Navicula está classificado na Família Naviculaceae e inclui, em seu ‘sensu stricto’, entre 250 e 300 espécies habitantes das águas doces e marinhas, que se caracterizam, principalmente, pela presença de estrias radiadas na região mediana da valva e pelas terminações proximais da rafe desviadas para o lado primário ou secundário da valva, onde se localiza a falha de Voigt. Em alguns casos, as terminações proximais da rafe são retas. Não existe publicação de cunho taxonômico exclusivo sobre representantes de Navicula realizada para o Estado de São Paulo. Por esta razão, o presente estudo visou a aprofundar o conhecimento taxonômico das espécies de Navicula ‘sensu stricto’ com base no estudo de populações amostradas de 32 reservatórios distribuídos em cinco bacias hidrográficas do Estado de São Paulo. O presente estudo foi realizado a partir da análise de 317 lâminas permanentes que abrangeram hábitats como fitoplâncton, perifíton e sedimentos superficiais. O material planctônico foi coletado com amostrador de van Dorn e rede de plâncton confeccionada com tecido de náilon de 20 μm de abertura de malha. O material perifítico foi recolhido a partir de substratos naturais (rochas ou macrófitas aquáticas) e o dos sedimentos superficiais foi coletado com testemunhador de gravidade, aproveitando os dois primeiros centímetros superficiais. Todas as amostras foram fixadas com solução aquosa de formalina a 3-5% e, em seguida, oxidadas e analisadas ao microscópio óptico. Foram identificadas 38 espécies e dois materiais em nível gênero; e todos foram descritos, ilustrados e comentados. Características morfológicas e métricas foram incluídas para todos os 40 táxons. Nenhum táxon teve ocorrência igual ou superior a 50% nas amostras analisadas, sendo Navicula notha (23% das amostras analisadas) a espécie que apresentou a maior frequência de ocorrência, seguida de N. cryptocephala (14,2%), N. rostellata (9,8%), N. neomundana (7,6%), N. breintenbuchii (6,6%), N. cryptotenella (5,4%), N. herbstiae (4,1%), N. symmetrica (3,8%) e N. radiosa (2,5%). Vinte e uma espécies foram identificadas pioneiramente para o Estado de São Paulo. Por fim, o presente estudo contribuiu para o conhecimento da biodiversidade de diatomáceas do Estado de São Paulo e o fornecimento de informação fundamental para outros estudos taxonômicos, ecológicos e demais que demandem a identificação adequada da alga estudada.
Genus Navicula is classified in the Family Naviculaceae and includes in its ‘sensu stricto’ between 250 and 300 species living in the fresh and marine waters, that are characteristic, mainly by the presence of radiating striae at the median portion of valves and the raphe proximal endings deviating to the valve primary or secondary side, where is located the Voigt discontinuity. In some instances, however, raphe proximal endings are straight. There is no publication dealing exclusively with the taxonomy of Navicula representatives for São Paulo State. For this reason, present study aimed at deepening the taxonomical knowledge of Navicula ‘sensu stricto’ species based on the study of populations sampled from 32 reservoirs distributed among five water basins of São Paulo State. Present study was based on the analyses of 317 permanent mountings that involved diferente habitats (phytoplankton, periphyton and surface sediments). Plankton material was gathered with a van Dorn sampler and a net built of a 20 μm mesh nylon fabric. Periphytic material was collected from natural substrates (rocks or aquatic macrophytes), and that of surface sediments by using a gravity corer using just the first two superficial centimeters. All samples were fixed and preserved with a formalin 3-5% water solution, and immediately after oxidated and observed under a light microscope. Thirty eight species were identified and two populations just to the genus level; all 40 materials were described, illustrated and commented. Morphological and metric characteristics were made available for all 40 taxa. No taxon had its occurrence ≥ 50% of total samples examined, Navicula notha (23% of samples analysed) being the species that showed the highest occurrence frequence, followed by N. cryptocephala (14.2%), N. rostellata (9.8%), N. neomundana (7.6%), N. breintenbuchii (6.6%), N. cryptotenella (5.4%), N. herbstiae (4.1%), N. symmetrica (3.8%) and N. radiosa (2.5%). Twenty one species were presently identified for the first time for São Paulo State. Finally, present study contributes to the knowledge of the diatoms biodiversity of São Paulo State, and provides fundamental information to other taxonomic, ecological, and other studies that will need the proper taxonomic identification of the alga studied.
Genus Navicula is classified in the Family Naviculaceae and includes in its ‘sensu stricto’ between 250 and 300 species living in the fresh and marine waters, that are characteristic, mainly by the presence of radiating striae at the median portion of valves and the raphe proximal endings deviating to the valve primary or secondary side, where is located the Voigt discontinuity. In some instances, however, raphe proximal endings are straight. There is no publication dealing exclusively with the taxonomy of Navicula representatives for São Paulo State. For this reason, present study aimed at deepening the taxonomical knowledge of Navicula ‘sensu stricto’ species based on the study of populations sampled from 32 reservoirs distributed among five water basins of São Paulo State. Present study was based on the analyses of 317 permanent mountings that involved diferente habitats (phytoplankton, periphyton and surface sediments). Plankton material was gathered with a van Dorn sampler and a net built of a 20 μm mesh nylon fabric. Periphytic material was collected from natural substrates (rocks or aquatic macrophytes), and that of surface sediments by using a gravity corer using just the first two superficial centimeters. All samples were fixed and preserved with a formalin 3-5% water solution, and immediately after oxidated and observed under a light microscope. Thirty eight species were identified and two populations just to the genus level; all 40 materials were described, illustrated and commented. Morphological and metric characteristics were made available for all 40 taxa. No taxon had its occurrence ≥ 50% of total samples examined, Navicula notha (23% of samples analysed) being the species that showed the highest occurrence frequence, followed by N. cryptocephala (14.2%), N. rostellata (9.8%), N. neomundana (7.6%), N. breintenbuchii (6.6%), N. cryptotenella (5.4%), N. herbstiae (4.1%), N. symmetrica (3.8%) and N. radiosa (2.5%). Twenty one species were presently identified for the first time for São Paulo State. Finally, present study contributes to the knowledge of the diatoms biodiversity of São Paulo State, and provides fundamental information to other taxonomic, ecological, and other studies that will need the proper taxonomic identification of the alga studied.
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Palavras-chave
Diatomáceas, Estado de São Paulo, Levantamento florístico, Navicula, Taxonomia, Diatoms, Floristic survey, Taxonomy