The aim was to characterize the karyotype of rodents of the genus Proechimys from three localities in the central Brazilian Amazon, in the search for new markers that might shed light on our understanding of the taxonomy and evolutionary history of this taxon. Two karyotypes were found, viz., 2n = 28, FN = 46 in individuals from the NRSP (Cuieiras River) and REMAN (Manaus), and 2n = 46, FN = 50 in individuals from the Balbina Hydroelectric Plant. While individuals with the karyotype with 2n = 28 chromosomes were morphologically associated with Proechimys cuvieri, their karyotype shared similarities with those of the same diploid number in two other regions. Although three karyotypes are described for Proechimys cuvieri, no geographic distribution pattern that defined a cline could be identified. Based on the morphological examination of voucher specimens and additional results from molecular analysis, the karyotype with 2n = 46 and FN = 50 could be associated with P. guyannensis.

We describe for the first time the karyotype of Glironia venusta (Didelphidae, Didelphimorphia), a rare South American marsupial. G. venusta has a diploid number 2n=18 and a number of autosomal arms NA=22. The diploid number of 18 chromosomes is somewhat unexpected, considering prior assignment of Glironia to the subfamily Caluromyinae (2n=14 in other species of the subfamily). The only other didelphid genus known to have 2n=18 chromosomes is Monodelphis. Chromosome banding, however, revealed a pattern closer to that observed for the 2n=14 species. Considering recent studies in didelphid phylogeny, wherein Glironia is sister to the remaining members of the family, the diploid number observed for Glironia may represent the ancestral state of the family, or may result from convergent evolution.

Se describe aquí por primera vez el cariotipo de Glironia venusta. El número diploide de G. venusta es 2n=18 y el número de brazos de autosómicos NA=22. El número diploide de 18 es un tanto inesperado, considerando la inclusión anterior de Glironia a la subfamilia Caluromyinae (2n=14 para las otras especies conocidas). El único otro género conocido de Didelphidae presentando 2n=18 es Monodelphis. Sin embargo, estudios de bandas de cromosomas muestran un patrón mas parecido al observado para las especies 2n=14. Considerando estudios recientes en la filogenia de los Didelphidae, donde se sugiere la hipótesis de que Glironia sea el grupo hermano de los restantes miembros existentes de esta familia, el número diploide observado puede representar el estado ancestral de la familia, o puede haber resultado de evolución convergente.

In a study aiming to describe the diet of Micoureus paraguayanus in a southeastern Brazilian Cerrado (savannah-like) remnant, we found young didelphid remains in fecal samples from live-trapped adults. These findings uncovered either events of scavenging on dead young didelphids or infanticide adding to the knowledge on the dietary breadth and behavioral ecology of M. paraguayanus.

En un estudio con el objetivo de describir la dieta de Micoureus paraguayanus en un remanente de Cerrado en el sudeste de Brasil, encontramos vestigios de didélfidos jóvenes en muestras de heces de adultos capturados. Estos resultados sugieren el consumo de individuos ya muertos o infanticidio. Nuestros hallazgos añaden un nuevo conocimiento acerca de la dieta y ecología conductual de M. paraguayanus.

Reportamos três novos espécimes de Neusticomys oypocki coletados numa paisagem de plantação silvicultural. Estes representam um terço de todos os espécimes de N. oyapocki conhecidos e ampliam a distribuição da espécie cerca de 360 km para o sul. Todos foram capturados com armadilhas de interceptação e queda, o que reforça a importância do método para inventários compreensivos de pequenos mamíferos. As capturas ocorreram durante a estação seca em florestas primária, secundária ou de plantação, sugerindo que as espécies de Neusticomys podem ser mais oportunistas e habitat generalistas do que aquilo pensado anteriormente.

Here we report three new specimens of Neusticomys oypocki from northeastern Brazilian Amazonia collected in a plantation forestry landscape. These represent one third of all known N. oyapocki specimens and extend the distribution of the species ca. 360 km southwards. All specimens were captured with pitfall traps, which reinforce the importance of this method for comprehensive small mammal inventories. Moreover, captures occurred during the dry season in primary, secondary, or plantation forests, suggesting that species of Neusticomys may be more opportunistic habitat generalists than previously thought.