Comparative cytogenetics of Physalaemus albifrons and Physalaemus cuvieri species groups (Anura, Leptodactylidae)

Recently, Physalaemus albifrons (Spix, 1824) was relocated from the P. cuvieri group to the same group as P. biligonigerus (Cope, 1861), P. marmoratus (Reinhardt & Lütken, 1862) and P. santafecinus Barrio, 1965. To contribute to the analysis of this proposition, we studied the karyotypes of P. albifrons, P. santafecinus and three species of the P. cuvieri group. The karyotype of P. santafecinus was found to be very similar to those of P. biligonigerus and P. marmoratus, which were previously described. A remarkable characteristic that these three species share is a conspicuous C-band that extends from the pericentromeric region almost to the telomere in the short arm of chromosome 3. This characteristic is not present in the P. albifrons karyotype and could be a synapomorphy of P. biligonigerus, P. marmoratus and P. santafecinus. The karyotype of P. santafecinus is also similar to those of P. marmoratus and P. biligonigerus owing to the presence of several terminal C-bands and the distal localization of the NOR in a small metacentric chromosome. In contrast, the P. albifrons karyotype has no terminal C-bands and its NOR is located interstitially in the long arm of submetacentric chromosome 8. The NOR-bearing chromosome of P. albifrons very closely resembles those found in P. albonotatus (Steindachner, 1864), P. cuqui Lobo, 1993 and some populations of P. cuvieri Fitzinger, 1826. Additionally, the P. albifrons karyotype has an interstitial C-band in chromosome 5 that has been exclusively observed in species of the P. cuvieri group. Therefore, we were not able to identify any chromosomal feature that supports the reallocation of P. albifrons.