We tested whether interindividual variations in diet composition within a population of Deuterodon stigmaturus can be explained by morphological differences between individuals, and whether diet-morphology relationships are dependent on the ontogenetic development. We analyzed diet of 75 specimens sampled in a coastal stream of Southern Brazil. Variation in stomach content was summarized with a Principal Coordinate Analysis (PCoA). The retained PCoA axes were tested as response to standard length (SL), and to values of intestine length (IL) and mouth length (ML) independent of body size, using linear mixed-effects models (LMM). The most consumed food items by D. stigmaturus were filamentous algae (41%), terrestrial plants (20.3%), detritus (12%), and aquatic invertebrates (8.8%). The LMMs showed that SL was positively related to consumption of terrestrial plants, whereas IL independent of SL was negatively related to aquatic invertebrates and positively related to filamentous algae. When body sized was held constant, ML was not related to diet variation. Interindividual diet differences conditioned to body size suggest that individuals shift their trophic niche and function in the ecosystem along the ontogenetic development. Relationships between intestine length and diet composition suggest interindividual differences in foraging ability and digestibility of distinct food items.Nós testamos se variações na composição da dieta de uma população de Deuterodon stigmaturus podem ser explicadas por diferenças morfológicas entre indivíduos, e se as relações entre morfologia e dieta são dependentes do desenvolvimento ontogenético. A dieta de 75 indivíduos amostrados em um riacho costeiro do sul do Brasil foi analisada. Uma Análise de Coordenadas Principais (PCoA) foi utilizada para sumarizar variações individuais no conteúdo estomacal. Os eixos retidos da PCoA foram testados como resposta ao comprimento padrão (CP) e ao comprimentos do intestino (CI) e da boca (CB), independentes do tamanho corporal, usando modelos lineares mistos (LMMs). Os itens macroscópicos mais consumidos por D. stigmaturus foram algas filamentosas (41%), plantas terrestres (20,3%), detritos (12%), e invertebrados terrestres (8,8%). Os LMMs mostraram que o CP foi positivamente relacionado ao consumo de plantas terrestres, enquanto que valores de CI independentes de CP foram negativamente relacionados ao consumo de invertebrados aquáticos e positivamente relacionados ao consumo de algas filamentosas. Quando o CP foi mantido constante, CB não foi relacionado a composição da dieta. As diferenças na dieta condicionadas ao tamanho corporal sugerem que os indivíduos mudam seu nicho trófico e função no ecossistema ao longo do desenvolvimento ontogenético. As relações entre o tamanho do intestino e composição da dieta sugerem diferenças individuais na habilidade de forragear e digerir itens alimentares distintos.Keywords: Characin, Coastal drainage, Feeding, Freshwater fish, Intraspecific variation.
IntroductionFreshwater fishes can exhibit a high degree...
-(Agaricomycetes fungi community at different forest systems in the northwest of Rio Grande do Sul State, Brazil: seasonal deciduous forest and eucalypt monoculture). Monocultures differ from native forests in relation to plant heterogeneity, variety of substrates, and soil humidity, possibly altering the diversity of organisms, such as the fungi. This study aimed to compare the richness, abundance, and composition of Agaricomycetes fungi in a native forest and in a eucalypt monoculture. The fungi were collected in a seasonal deciduous forest area and in a Eucalyptus grandis monoculture, in the northwest of Rio Grande do Sul State, Brazil. The abundance and richness of fungi were significantly lower in the eucalypt plantation than in the native forest and the species composition differed between the areas. Thus, it was concluded that the eucalypt monoculture negatively affects the Agaricomycetes fungi community. Keywords: Basidiomycota, Eucalyptus grandis, native forest RESUMO -(Comunidade de fungos Agaricomycetes em diferentes sistemas florestais no noroeste do Estado do Rio Grande do Sul, Brasil: Floresta Estacional Decídua e monocultura de eucalipto). As monoculturas diferem de matas nativas em relação à heterogeneidade vegetal, variedade de substratos e umidade do solo, podendo afetar a diversidade de organismos, tais como os fungos. O objetivo deste trabalho foi comparar a riqueza, abundância e composição de fungos Agaricomycetes em uma mata nativa e em uma monocultura de eucalipto. As coletas dos fungos foram realizadas em uma área de Floresta Estacional Decídua e em uma monocultura de Eucalyptus grandis, no noroeste do Estado do Rio Grande do Sul, Brasil. A abundância e riqueza de fungos na monocultura de eucalipto foram significativamente inferiores às encontradas na mata nativa, assim como a composição de espécies diferiu entre as áreas. Portanto, a monocultura de eucalipto afeta negativamente a comunidade de fungos Agaricomycetes. Palavras-chave: Basidiomycota, Eucalyptus grandis, mata nativa
Some exotic species threat the integrity of natural environments due to their invasive potential. They can affect other species by releasing secondary compounds in the soil. Morus nigra (Moraceae) is an invasive species of riparian forests in southern Brazil. The objective of this study was to verify if the aqueous extracts of fruit, fresh and dry leaves of M. nigra show phytotoxic effects on germination, seedling growth and membrane integrity of seedlings of Lactuca sativa. Extract concentrations of 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5 and 10% were tested. Germination rate and speed of germination were determined. Effects on initial growth were evaluated by measuring seedling root and shoot length, and membrane integrity was assessed by conductivity tests. Results showed the phytotoxicity of M. nigra aqueous extracts, causing significant inhibition on germination and seedling growth. The fruit extract was generally less phytotoxic than extracts from fresh and dry leaves. Moreover, the extracts induced changes in membrane integrity and caused morphological deformities in seedlings, such as necrotic roots and chlorotic plants. The high phytotoxicity of fruit, dry and fresh leaf extracts of M. nigra was evidenced, indicating the allelopathic potential of the species.
Medicinal plants (e.g. Discaria americana) have been used by populations for centuries. However, popular use is not enough to validate these plants as safe and effective medicinal products. The present study sought to evaluate the acute and subacute toxicity as well as the anxiolytic and antinociceptive effects of D. americana root bark and aerial parts extracts in mice. In acute toxicity studies, mice were treated with single intraperitoneal doses of the aforementioned extracts. Subacute toxicity studies were performed by oral administration of the extracts over 14 days. Anxiolytic studies consisted of the elevated plus maze method, and antinociceptive studies were based on the hot plate test. The LD50 value for D. americana aerial parts extract was established at >500 mg/kg, and for the root bark extract, 400 mg/kg. D. americana aerial parts extract produced anxiolytic (250 mg/kg) and antinociceptive effects (125, 200 and 250 mg/kg). Conversely, D. americana root bark extract showed neither anxiolytic nor antinociceptive effects in mice.
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