Comparative cytogenetics of spiny rats of the genus proechimys (Rodentia, Echimyidae) from the Amazon region

We made a comparative analysis of the cytogenetics of spiny rat species of the genus Proechimys collected from several sites of the Madeira River basin (Amazonas State, Brazil) and Jari River valley (Pará State, Brazil). Individuals were assigned to three groups based on diploid and fundamental numbers: 2n=28, FN=46 (P. cuvieri and P. gr. longicaudatus); 2n=38, FN=52 (Proechimys gr. guyannensis), and 2n=40, FN=54 (P. gardneri). The nucleolar organizer region (NOR) was interstitial on the long arm of one submetacentric pair, as seen in all species of Proechimys analyzed thus far. However, its position in the karyotype was variable. A duplication of the NOR in one of the homologues was detected in P. gr. longicaudatus from the Aripuanã basin along the mid Madeira. The C-band pattern varied between species and, together with the NOR, allowed the identification of two evolutionary units in P. gr. longicaudatus in the region of the mid Madeira River (cytotypes A and B). The morphology and banding of the sex chromosomes were species specific. A range extension is suggested for the geographic distribution of P. gardneri and P. gr. longicaudatus. Moreover, we suggest that species of Proechimys with 2n=38 chromosomes are restricted to east of the Negro River and north of the Amazon River. We also revised the published chromosome data available for Proechimys. © FUNPEC-RP

Gracilinanus microtarsus (Didelphimorphia: Didelphidae)

Gracilinanus microtarsus (J. A. Wagner, 1842), called the Brazilian gracile opossum, is a small didelphid that is 1 of 6 species in the genus Gracilinanus. It is a sexually dimorphic, solitary marsupial that has a highly seasonal reproductive pattern. It inhabits Atlantic rain forests and semideciduous forests interspersed in the highly seasonal cerrado (savanna-like vegetation) in southeastern and southern Brazil. It prefers locations associated with low canopy cover and it also occurs in habitats altered by anthropogenic events. The species is classified as Least Concern by the International Union for Conservation of Nature and Natural Resources. © 25 March 2010 by the American Society of Mammalogists

Consumo de crías de didélfidos por Micoureus paraguayanus (Didelphimorphia: Didelphidae) en el sudeste de Brasil

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. © SAREM, 2010