Abstract Cytogenetic data can be useful for taxonomic and phylogenetic studies, as well as to provide information about chromosome evolution. Therefore, it may help design conservation priorities for some threatened species, such as anurans. Herein, we describe the karyotypes of Scinax constrictus and Ololygon centralis, native endemic species from the Brazilian Cerrado. Chromosome preparations for both species were stained with Giemsa for morphological analyses and then impregnated by the Ag-NOR method for localization of the nucleolar organizer region (NOR). Both species had 24 chromosomes, as confirmed by meiotic analyses, which showed 12 bivalents. Chromosome morphologies presented the same pattern for Scinax and Ololygon compared to species already karyotyped in both genera. The NOR was interstitially located in the long arm of pair 7 in S. constrictus, whereas in O. centralis it was found near the centromere in the long arm of pair 1, thus diverging from what is commonly found for other Ololygon species. Therefore, we provide the first description of the karyotype of O. centralis and the first report of the localization of the NOR for the karyotype of both species. Our study increases the cytogenetic knowledge in species of the genera Scinax and Ololygon, and provide support for further studies on the taxonomy, ecology, and evolution of hylid anurans.

BACKGROUND: Biotic processes, such as predation and parasitism events, are crucial for answering questions in ecology and evolution. Here, we report predation and ectoparasitism events of invertebrates upon tadpoles in aquatic habitats of southern Brazil. FINDINGS: Four lentic water bodies were sampled twice a month (December 2012 to March 2013). Those water bodies were located in the Diamante do Norte County, State of Paraná, southern Brazil. The tadpoles, Dendropsophus aff. minutus, Hypsiboas raniceps, Scinax fuscovarius, Physalaemus cuvieri and Elachistocleis bicolor were observed being predated by six different invertebrate predators. However, Leptodactylus fuscus and Pseudis sp. were also recorded on the same water bodies and were not observed being preyed or parasitized. The most abundant predator in our sampling areas was the diving beetle larvae. We observed a static and escape behavior of tadpoles when in close proximity to predators and constant movements in E. bicolor tadpoles, which can be advantageous for invertebrate predators. Parasitism events included D. aff. minutus, S. fuscovarius,andE. bicolor tadpoles that were infected by a single leech. The ectoparasites anchor the posterior sucker on the host tadpole during the blood feeding. CONCLUSIONS: Even isolated reports of ecological interactions are important for understanding ecological communities and the impacts of parasites and predators on tadpoles' populations. Additionally, these interactions can help to understand the ecology behavior of the organisms.

O Cerrado é o segundo maior bioma brasileiro e é considerado um dos mais importantes hotspots de biodiversidade. Neste bioma foram registradas cerca de 150 espécies de anuros, das quais 30% são endêmicas. Entretanto, existem muitas áreas ainda não inventariadas, nas quais não se conhece quase nada sobre a diversidade de anuros. Assim, neste estudo apresentamos informações referentes a anurofauna do sudoeste do Estado de Goiás (Brasil Central), a qual vem sendo modificada principalmente pela agropecuária. Nesta região, 45 corpos d'água foram amostrados entre os meses de novembro/2007 a fevereiro/2008 e novembro/2008 a março/2009, localizados próximos a plantações de soja, cana-de-açúcar, pastagem e vegetação nativa. No total, foram registrados adultos e girinos de 36 espécies de anuros, a maioria comum de áreas abertas. As curvas de acumulação de espécies, tanto para adultos quanto para girinos, apresentaram a formação de uma assíntota, o que indica uma baixa probabilidade de registro de novas espécies mesmo com a amostragem de outros corpos d'água. Nesta área com forte influência de impactos agrícolas, a riqueza encontrada representa aproximadamente 1/4 do total de espécies conhecidas para o bioma Cerrado.

The Cerrado is the second largest biome in Brazil and is considered one of most important among the biodiversity hotspots. In this biome can be found about 150 anurans species, from which 30% are endemic. However, there are many Cerrado areas that have little information gathered about the anuran biodiversity. Thus, in this study we present the result of an inventory of anurans species from the southwest region of Goiás State (Central Brazil). In this region, we sampled 45 water bodies, located near soybean and sugar-cane cultures, pastures and natural vegetation, from November/2007 to February/2008 and from November/2008 to March/2009. Altogether, adults and tadpoles of 36 species were registered, with the majority of species registered in association to open areas. The rarefied curve of species richness show an asymptote formation, which indicates that the chance to add species to the inventory is low, even with additional habitats sampling. Therefore, our results reveal high species richness in the present sampled region, which represented almost one fourth of all species found in Cerrado.