Araçá Bay, located in the city of São Sebastião, São Paulo, Brazil, is a protected area of substantial complexity. It represents the last remaining mangrove swamp preserve between the cities of Bertioga and Ubatuba on the northern coast of São Paulo State. This mangrove swamp has specific physical and chemical properties, and it shelters a wide variety of life, including fungi. These microorganisms are present in a variety of species with different morphophysiological features, and they have the ability to produce enzymes of biotechnological importance. The goal of this study was to quantify, isolate, and identify filamentous fungi in water and sediment samples from the Araçá Bay mangrove swamp in São Sebastião. Two samplings were performed in the summer and two were performed in the winter. The samples were collected from intertidal zones, and dissolved oxygen (DO), temperature, salinity, and pH were measured in situ. The spread plate technique was used to inoculate the samples collected on plates with a potato dextrose agar (PDA) medium. A total of 208 colonies (68 from water samples and 140 from sediment samples) were isolated, and they were identified based on their morphological characteristics. Filamentous fungus density was higher in the sediment than in the water, and the samplings performed in the winter revealed a higher density than those performed in the summer. Though some of the environmental parameters were not ideal for fungal development, a high quantity of growth was nevertheless observed. When the isolated colonies were analyzed, the greatest diversity and species richness were found in the summer samples. The genera identified in all of the samples were Aspergillus, Penicillium, Cladosporium, and Fusarium. The pathogenic species found from these genera were Aspergillus fumigatus, A. terreus, Penicillium citrinum, and P. chrysogenum. These species are also able to produce enzymes that offer a variety of applications. The fungal community described herein represents the diversity found in this mangrove swamp during the period studied. Many of the fungus species found are pathogenic and may be useful due to their ability to produce specific enzymes applicable in the biotechnological and pharmaceutical industries. Keywords: Mangrove swamp, Environmental parameters, Mycology. Densidade e diversidade de fungos filamentosos na água e sedimento da Baía do Araçá, São Sebastião (SP), BrasilResumo: A Baía do Araçá, localizada no município de São Sebastião (SP), é uma região protegida, de grande complexidade, mantendo o último remanescente preservado de manguezal entre Bertioga e Ubatuba, litoral Norte do Estado de São Paulo. Manguezal caracteriza-se com propriedades físico-químicas específicas e abriga grande diversidade de seres vivos, entre eles os fungos. Estes microrganismos apresentam grande variedade de espécies e diferentes características morfofisiológicas com capacidade de produzir algumas enzimas de importância biotecnológica. Este trabalho teve como objetivo quantificar, isolar e id...

Symbiotic relations are present in the nature and can contribute to the success of the organisms involved. Endophytic fungi live within the leaf tissues without causing any harm to the host plant, and some of them can be a defense mechanism against the attack by the leaf-cutting ants. Ants of the genus Atta are known as leaf-cutting ants and have an obligatory association with the fungus Leucoagaricus gongylophorus, cutting pieces of leaves and bringing them back to the colony to the fungus. The present study aimed to find out the endophytic fungi community of an attractive plant (Acalypha wilkesiana) and a less attractive plant (Colocasia esculenta) to the ants Atta sexdens. We found out that the communities are different in quantity and in composition and 73% of the isolated fungi were from A. wilkesiana, which has fungi known as attractive to leaf-cutting ants, such as genus Colletotrichum, Pestalotiopsis, Phomopsis and Xylaria. On the other hand, in C. esculenta, there was found the genus Fusarium, known to be reject by the leafcutting ants, and less fungal diversity than in the attractive plant A. wilkesiana. Therefore, our data suggest that attractivity or repelence of a plant to the leaf-cutting ants could be related to presence or ausence of determinated fungi more than the quantity of fungi present in a leaf.