1. Waterbird-mediated endozoochory is an essential mechanism for the dispersal of sessile organisms in freshwater ecosystems. However, in the neotropics there are no previous studies of how different waterbird species vary in the dispersal functions they perform, and how seasonality influences endozoochory. In this study, we identified plant diaspores dispersed in faeces of five South American waterfowl (Brazilian teal Amazonetta brasiliensis, yellow-billed teal Anas flavirostris, ringed teal Callonetta leucophrys, coscoroba swan Coscoroba coscoroba, and whitefaced whistling-duck Dendrocygna viduata). 2. We collected 165 faecal samples from five wetlands in southern Brazil surrounded by pasture and rice fields, then separated and measured intact seeds and other diaspores. Using generalised linear models, we tested how diaspore abundance and taxonomic richness differed among bird species and between cold (April-September) and warm (October-March) periods. We also analysed bird-specific and seasonal variations in diaspore composition through principal coordinates analysis and permutational multivariate analysis of variance. We used indicator species analysis to determine which diaspore species discriminated between bird species and seasons. Finally, we measured diaspore length in order to analyse differences among waterfowl species in the size of diaspores dispersed. 3. We found 2,066 intact diaspores from 40 different plant taxa, including seeds of 37 angiosperms and diaspores of Lycophyta (Isoetes cf. maxima), Pteridophyta (Azolla filiculoides), and Charophyceae. There was at least one diaspore in 65% of all faecal samples. Diaspores of native amphibious and emergent plants were dominant. We found 1,835 diaspores (from 33 taxa) in the cold period but only 231 (23 taxa) in the warm period. Seeds of the grass Zizaniopsis bonariensis and of the sedge Rynchospora sp. were the most abundant taxa. A strong interaction between bird species and season was the most important predictor of variation in both taxonomic richness and abundance of diaspores. The taxonomic composition of diaspores differed among waterfowl species and season. Indicator species analysis identified 12 plant taxa associated with particular bird species and seasons. Coscoroba swan, the largest bodied species in our study dispersed a higher proportion (8.2%) of large (length >2 mm) seeds. | 79 SILVA et AL.

For the first time to our knowledge, we demonstrate that whole angiosperm individuals can survive gut passage through birds, and that this occurs in the field. Floating plants of the genus Wolffia are the smallest of all flowering plants. Fresh droppings of white-faced whistling duck Dendrocygna viduata (n ¼ 49) and coscoroba swan Coscoroba coscoroba (n ¼ 22) were collected from Brazilian wetlands. Intact Wolffia columbiana were recovered from 16% of D. viduata and 32% of Coscoroba samples (total ¼ 164 plantlets). The viability of plants was tested, and asexual reproduction was confirmed. Wolffia columbiana is an expanding alien in Europe. Avian endozoochory of asexual angiosperm propagules may be an important, overlooked dispersal means for aquatic plants, and may contribute to the invasive character of alien species.

No abstract

Oxidative stress plays an important role in the evolution of aging and life history. High investments in life-history traits and environmental conditions can be associated with increased oxidative stress and aging process. However, to date, most studies that investigated variations in oxidative status were performed with long-lived vertebrates. Studies with short-lived vertebrates in wild are nonexistent. Annual killifishes have the shortest lifespans among vertebrates and inhabit temporary ponds subject to large variations in environmental conditions. In this sense, we investigated whether the high investment in growth and reproduction in a short-lived vertebrate and the large variations in environment has any cost in susceptibility to oxidative stress. We assessed the seasonal variation and the environmental correlates of four different oxidative status markers (lipid peroxidation and activity of the antioxidant enzymes Superoxide Dismutase, Catalase and Glutathione S-Transferase) along the life cycle of wild individuals of the Neotropical annual fish Austrolebias minuano. Males showed reduction in all biomarkers (except proteins) along their life cycle, while females showed increased oxidative stress only in the growth period. In addition, we showed that water physicochemical parameters, habitat structure and presence of cooccurring killifish species influenced the seasonal variation of the biomarkers. A. minuano showed an efficient antioxidant system for most part of their life cycle (mainly in males), suggesting a well-developed oxidative stress regulation system. We also show that annual fish mortality (mainly in males) apparently is not related to oxidative stress. Thus, environmental factors should drive annual fish aging and mortality.

Aging processes have become an attractive field for researchers and annual fish have been used as biological models. However, the study on the changes in age-associated markers during the normal aging in wild populations of annual fish remains open. Austrolebias is a genus of Neotropical annual killifishes, distributed mainly in ephemeral pools across grassland floodplains of temperate South America and represent an emerging biological model for aging research, but studies investigating rapid aging and senescence in this genus of annual fish are almost nonexistent. This study was undertaken to examine the changes in age-associated liver markers at the different developmental stages in wild populations of Austrolebias minuano. We demonstrate that A. minuano has a number of liver alterations of different severities throughout the life cycle, suggesting that these changes tend to increase with age. Our results revealed that [ 70% of the analyzed livers presented alterations. Thus, our study should instigate new approaches on aging using Neotropical annual fish, and could be useful to improve the knowledge already provided by consecrated biological aging models as e.g. Nothobranchius killifishes.