The karyotypes of Phyllostomus discolor and P. hastatus from Eastern Amazonia were studied by G-, C-, G/C sequential and Ag-NOR techniques. Both species presented 2n = 32, with the autosome complement composed of 30 bi-armed in P. discolor and 28 bi-armed plus 1 acrocentric in P. hastatus. In both species, the X chromosome is medium submetacentric while the Y is minute acrocentric. The present study found only one difference between the karyotypes of P. discolor and P. hastatus: the smallest autosome (pair 15) is bi-armed in discolor and acrocentric in hastatus, a result best explained by pericentric inversion. The C-banding revealed constitutive heterochromatin only at the centromeric regions of all chromosomes, with the NOR site located at the distal region of short arm of pair 15, in both species. The taxon P. discolor is considered primitive for genus Phyllostomus and the bi-armed form of pair 15 is the assumed primitive condition which, rearranged by a pericentric inversion originated the acrocentric from found in P. hastatus.
Meiotic analyses of the sex chromosomes were made in two different species belonging to the subfamily Carollinae (Phyllostomidae, Chiroptera): Rhinophylla pumilio and Carollia perspicillata. These species have different sex chromosome systems. Through banding techniques, chromosomes homologies between Carollia perspicillata and Rhinophylla pumilio were not found, possibly because Carollia species have highly rearranged chromosomes. Probably, Rhinophylla is better associated to Phyllostomini tribe. Sex vesicle pairing behavior at the meiotic prophase was analyzed in both species. R. pumilio had a simple sex chromosome system (XX/XY), the XY pair showed an asynchronic behavior compared to the autosomal bivalents. The sex vesicle showes the X and Y pairing in the pseudoautosomal region. Moreover, a folding of the X-asynaptic axis on itself and condensed differentiated axes were also identified. In C. perspicillata, with a multiple sex chromosome system (XY 1 Y 2), the segments Xp-Y 1 and Xq-Y 2 paired independently from each other. Compared to the autosomes, the sex vesicle showed a precocious pairing behavior. In C. perspicillata, a NOR stained with silver was localized in the X rearranged chromosome. Possibly, this region separates the XY 1 Y 2 trivalent in two independent parts: one involving the X and Y 2 autosomal with transcriptional activity, and the other corresponding to the original X and Y sex pair.
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