Rodents constitute one of the most diversified mammalian orders. Due to the morphological similarity in many of the groups, their taxonomy is controversial. Karyotype information proved to be an important tool for distinguishing some species because some of them are species-specific. Additionally, rodents can be an excellent model for chromosome evolution studies since many rearrangements have been described in this group.This work brings a review of cytogenetic data of Brazilian rodents, with information about diploid and fundamental numbers, polymorphisms, and geographical distribution. We point out that, even with the recent efforts on cytogenetic studies in this group, many species lack karyotypic data. Moreover, we describe for the first time the karyotype of Carterodon sulcidens (Lund, 1838) (Family Echimyidae), a new fundamental number for an undescribed species of Neacomys Thomas, 1900 (Family Cricetidae, Subfamily Sigmodontinae), and illustrate the karyotype of a Brazilian specimen of Mus musculus Linnaeus, 1758 (Family Muridae). This review compiles the cytogenetic data on Brazilian rodents reported in the last three decades, after the last revision published in 1984, including synonyms, chromosomal variations, and geographic distribution. Additionally, it also reinforces that Brazilian biodiversity is still poorly known, considering the new data reported here.

Industrial areas on estuarine systems are commonly affected by heavy metals, affecting all local biota. Random Amplified Polymorphic DNA (RAPD) was used to evaluate genetic diversity of Ucides cordatus at mangroves in southeastern Brazil (Juréia, J; São Vicente, SV; and Cubatão, C), with distinct pollution levels by metals. The genetic diversity of this species was compared with concentrations of metals (Cd, Pb, Cu, Cr and Hg) in the environment. A pollution gradient was confirmed (SV>C>J), with low levels detected in water, except for mercury in SV. All metals in the sediment samples were below Threshold Effect Level (TEL), without an apparent biological risk to the biota. Genetic distance was very similar between J and C, with SV occurring as an out-group. RAPD was a powerful tool to investigate the effect of metal pollution on genetic diversity of this mangrove crab, and to evaluate the conservation status of the mangrove ecosystem.

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and snakes are a good example of it, considering their large adaptive radiation and morphological diversification (Greene, 1997).The habitat, in particular the substrate used by snakes, seems to have influenced body shape modifications (Cadle & Greene, 1993), and several morphological syndromes may be recognized (cf.

Some species have evolved conspicuous coloration that acts as a warning signal to predators. This defense mechanism is known as aposematism (Poulton, 1890). Because predators avoid attacking aposematic organisms, other palatable or harmless species are sometimes observed to mimic aposematic noxious organisms. This tactic is called Batesian mimicry (Bates, 1862). Additionally, some warning signals of different aposematic noxious species converge (Müller, 1879), which is classified as Müllerian mimicry. Müllerian mimics benefit from sharing the same (or similar) warning signal because they share the "cost" of educating predators to avoid the signal (Huheey, 1961; Wickler, 1968). These are only two mimicry categories among many others that have been proposed according to the noxiousness of both models and mimics (Balogh, Gamberale