The study of the feeding ecology of amphibians is an old issue in herpetology. Notwithstanding, the lack of food resources data in many studies of amphibians feeding has lead to partial understanding of frog feeding strategies. In this study we evaluate the trophic selectivity of a red spotted green frog (Hypsiboas punctatus) population from a Middle Paraná River floodplain pond in Argentina, and discuss the importance of prey availability data when interpreting results from diet analysis. We analyzed the gut contents of 47 H. punctatus adults and compared frog's diet with the environmental food resources. Prey availability was estimated by systematically seep-netting the microhabitat where anurans were localized foraging. We identified 33 taxonomic categories from gastrointestinal contents. Numerically, the most important prey categories were dipterans, followed by hemipterans, homopterans and coleopterans. The diet similarity between males and females was high and no statistical differences in diet composition were found. The most abundant food resources in the environment were dipterans, coleopterans, homopterans and collembolans. In order to assess whether frogs were selecting their preys, we calculated Pianka's niche overlap index and Jacobs electivity index comparing gut contents to prey availability data. Trophic niche overlap was medium but significantly higher than expected by chance. The electivity index indicated that H. punctatus foraged dipterans slightly above their environmental abundance. Among the secondary preys, hemipterans were foraged selectively, homopterans were consumed in the same proportion to their occurrence in the environment, coleopterans were foraged quite under their availability and collembolans were practically ignored by frogs. Without food resources data, H. punctatus could be classified as a specialist feeder, but dipterans also were quite abundant in the environment. Our results show that H. punctatus fit better as a generalist feeder, foraging on their main food item and some secondary preys in similar proportion to their environmental availability; even though other secondary preys are being selectively preferred or ignored by frogs. Our data illustrate the importance of including the resource availability data on diet studies to improve the understanding of amphibian feeding ecology.

We present the first data on age structure, growth pattern, and lines of arrested growth (LAG) for Leptodactylus latrans in temperate wetlands. Based on these data, we estimate LAG periodicity, age, size at sexual maturity and longevity for this species. We also tested for differences of these parameters between sexes. The age was determined through skeletochronology. Female maturity was determined by presence of differentiated ova, while male maturity was assessed through histological analysis to evaluate spermatozoid production. To establish whether this species marks one LAG per year, eight individuals were kept one year in captivity. For each specimen, LAG was compared for different phalanges of the same toe clipped at start and end of captivity. Leptodactylus latrans marked one LAG per year, indicating a growth rhythm adjusted to a seasonal environment and mainly driven by genetic factors. Longevity was five years for both sexes and frogs reached sexual maturity during the first year, exhibiting a reproductive lifespan of four years. Sexual maturity was related to a minimal size of 60 mm or a body mass of around 33 g. There was no difference in either size or growth pattern between sexes. The von Bertalanffy growth model showed that L. latrans grows fast after metamorphosis and their growth rate strongly decreases at about three years, probably due to the increased allocation of energy to reproduction. The high growth rates and early sexual maturation of L. latrans would allow an elevated rate of population renewal.

Natural products represent a rich source of bioactive compounds that have been historically used to obtain substances with great medicinal potential. The skin of anuran amphibians is a rich source of compounds with a wide range of biological activity. Alzheimer's disease (AD) is a complex disease associated with all kind of different pathways, making their simultaneous modulation necessary. Nowadays anti-AD treatments are focused on enzymatic inhibitors. Here in we report the activity of skin extracts from nine species from Argentina, belonging to three anuran families, as inhibitors of AChE, BChE and MAO-B enzymes. The extracts also showed antioxidant activities, acting as multi-target on four important pathways of AD.