The crab-eating fox, Cerdocyon thous (Linnaeus, 1766), is a small canid with twilight and nocturnal habits from savannas and forests of South America. In this study, we seasonally determined and quantified the diet of C. thous in Lami Biological Reserve, a conservation unit with 179.78ha situated in a suburban area in the municipality of Porto Alegre, southern Brazil. During the year 2000, we collected 80 fecal samples - 20 for each season - in two or three week sampling intervals, along trails inside the Reserve. Samples were dried in an oven for 24h at 60ºC, immersed in 70% alcohol, and prey items were identified using a stereomicroscope. The diet of the crab-eating fox was essentially carnivorous (87.62% composed by vertebrates), with seasonal variation (p = 0.0009) and absence of fruits. Small non-flying mammals and birds were the most frequent prey, being proportionally more preyed in autumn and summer, respectively. Arthropods were more preyed in winter and spring and bird/reptile eggs only in summer and spring, in the reproduction period of these groups.

All available published cytogenetic data show the presence of 28 different karyotypes in 311 specimens of A. cursor as an exceptional example of high karyotype variability in a single species. Our present sample of 116 animals collected in the rain forest of the Atlantic coast of the states of São Paulo and Bahia, Brazil, show 25 karyotype constitutions. The diploid number (2n) ranged from 16 to 14, and the number of autosomal arms (NF) from 26 to 18, because of centric fusion and pericentric inversions involving two autosome pairs, pericentric inversions in three other chromosome pairs, trisomy in the pair 7 and the presence of two XO females. Synaptonemal complex analysis, associated with data from experimental cross-breeding, suggested that heterozygous individuals for pericentric inversions have normal fertility. In this paper, we have reviewed the chromosomal data of this species, and have thus standardized the karyotype description and chromosome numbering. We discuss about karyotype evolution of Akodon cursor based on the frequency and constitution of karyotypes of all different geographical samples described so far in the literature.

Comparative studies among four species – Akodonazarae (2n = 38), A. lindberghi (2n = 42), A. paranaensis (2n = 44) and A. serrensis (2n = 46) – employing classic cytogenetics (C- and G-bands) and fluorescence in situ hybridization with telomeric (TTAGGG)_n sequencesare reported here. Non-telomeric signals in addition to the regular telomeric sites were detected in three species:A. azarae, A. lindberghi and A. serrensis. One interstitial telomeric site (ITS) was observed proximally at the long arm of chromosome 1 of A. azarae. The comparison of G-banding patterns among the species indicated that the ITS was due to a tandem fusion/fission rearrangement. Non-telomeric signals of A. lindberghi and A. serrensis were not related to chromosomal rearrangements; instead, the sequences co-localized with (i) heterochromatic regions of all chromosomes in A. serrensis; (ii) some heterochromatic regions in A. lindberghi, and (iii) both euchromatic and heterochromatic regions in the metacentric pair of A. lindberghi. These exceptional findings revealed that ITS in Akodon can be related to chromosomal rearrangements and repetitive sequences in the constitutive heterochromatin and that the richness of TTAGGG-like sequences in the euchromatin could be hypothesized to be a result of amplification of the referred sequence along the chromosome arms.

No abstract

Oryzomyini is the richest tribe among the Sigmodontine rodents, encompassing 32 living and extinct genera and including an increasing number of recently described species and genera. Some Oryzomyini are tetralophodont showing a reduction in the number of molar folds to four, while most taxa in this tribe retain the plesiomorphic pentalophodont state. We applied phylogenetic methods, molecular dating techniques and ancestral area analyses to members of an oryzomyini clade informally named ‘D’ in former studies and included related fossil tetralophodont forms. Based on 98 morphological characters and sequences of five gene fragments, we found that the tetralophodont condition is paraphyletic. Among living taxa, Pseudoryzomys is sister to Holochilus, and Lundomys is derived from a basal divergence. A clade formed by living Holochilus and the fossils Noronhomys and Carletonomys is sister to Holochilus primigenus, making Holochilus paraphyletic. Therefore, we describe a new genus that accommodates the fossil H. primigenus. Because trans‐Andean taxa currently share a common ancestor with taxa of cis‐Adean distribution, the northern Andes uplift may have worked as a postdispersal barrier. The tetralophodont lineages diverged during the Pliocene from a cis‐Andean ancestor, and the Great Plains in South America may have favoured the diversification of tetralophodont forms adapted to open habitats during the Pliocene.

Between 2000 and 2010, digestive tracts collected from carnivore carcasses found in southern Brazil were analyzed to determine the frequency and proportion of items constituting the diets of each species. Material was collected and analyzed from 194 animals of 10 species: Cerdocyon thous, Lycalopex gymnocercus (Canidae), Procyon cancrivorus (Procyonidae), Galictis cuja (Mustelidae), Conepatus chinga (Mephitidae), Leopardus colocolo, Leopardus geoffroyi, Leopardus guttulus, Leopardus wiedii, and Puma yagouaroundi (Felidae). Most of these species are sympatric, which makes them potential competitors when sharing, to a greater or lesser degree, the same resources. The food niche breadth was relatively narrow, demonstrating that even generalist species, such as the crab-eating raccoon, used food resources rather unequally. An extensive overlap ( > 90%) in food niches was found among the cat species, the grison, and the Pampas fox, which had diets based on rodents. Crab-eating raccoons occupied a different food niche, based on aquatic or semiaquatic prey and fruits. Conepatus chinga was unique in exploiting arthropods and insect larvae as basic dietary items.

No abstract

No abstract