Chromosomal analysis of Physalaemus kroyeri and Physalaemus cicada (Anura, Leptodactylidae)

All the species of Physalaemus Fitzinger, 1826 karyotyped up until now have been classified as 2n = 22. The species of the Physalaemus cuvieri group analyzed by C-banding present a block of heterochromatin in the interstitial region of the short arm of pair 5. Physalaemus cicada Bokermann, 1966 has been considered to be a member of the Physalaemus cuvieri species group, although its interspecific phylogenetic relationships remain unknown. The PcP190 satellite DNA has been mapped on the chromosomes of most of the species of the Physalaemus cuvieri group. For two species, Physalaemus cicada and Physalaemus kroyeri (Reinhardt & Lütken, 1862), however, only the chromosome number and morphology are known. Given this, the objective of the present study was to analyze the chromosomes of Physalaemus cicada and Physalaemus kroyeri, primarily by C-banding and PcP190 mapping. The results indicate that Physalaemus kroyeri and Physalaemus cicada have similar karyotypes, which were typical of Physalaemus. In both species, the NORs are located on the long arm of pair 8, and the C-banding indicated that, among other features, Physalaemus kroyeri has the interstitial band on chromosome 5, which is however absent in Physalaemus cicada. Even so, a number of telomeric bands were observed in Physalaemus cicada. The mapping of the PcP190 satellite DNA highlighted areas of the centromeric region of the chromosomes of pair 1 in both species, although in Physalaemus kroyeri, heteromorphism was also observed in pair 3. The cytogenetic evidence does not support the inclusion of Physalaemus cicada in the Physalaemus cuvieri group. In the case of Physalaemus kroyeri, the interstitial band on pair 5 is consistent with the existence of a cytogenetic synapomorphy in the Physalaemus cuvieri species group.