A high level of cytogenetic variation in Physalaemus ephippifer (Anura: Leiuperidae)

JULIANA NASCIMENTO; JUCIVALDO DIAS LIMA; PABLO SUÁREZ; LUCIANA BOLSONI LOURENÇO

Foz do Iguaçu

Congreso; 58o Congresso Brasileiro de Genética; 2012

Sociedade Brasileira de Genética

Physalaemus ephippifer is a leiuperid species that is found at the mouth of the Amazon River in Brazil and possibly in Guyana. However, some questions regarding the geographic distribution of this species exist, and the potential presence of undescribed species cannot be ruled out. Cytogenetic analyses of P. ephippifer specimens from Belém-PA have shown an interesting heteromorphism of the nucleolar organizer region (NOR) and C-banding in chromosome pair 8 that is exclusive to females. The presumed Z and W chromosomes had a terminal NOR on the long arm, but the W chromosome differed from the Z chromosome by the presence of an additional segment on the short arm. To provide additional cytogenetic data for P. ephippifer, male specimens from Pará localities (Monte Alegre, Óbidos, Alenquer, Curuá, Cedere I, Prainha) and Viruá-Roraima were analyzed cytogenetically. Chromosome preparations were obtained from intestinal cell suspensions and subjected to conventional staining using Giemsa, C-banding, DAPI-staining of C-banded metaphases, silver staining and FISH with the repetitive DNA probe Pep194. All of the male karyotypes in the study were very similar, but a differential NOR distribution pattern in the presumed sex chromosome pair 8 was observed among the populations. In the karyotypes of the 6 males from Cedere I an NOR was located terminally on 8q, as in the karyotypes already described for this species. In addition, a second NOR adjacent to the first was also present in this chromosome pair. The karyotypes of specimens from Prainha, Monte Alegre, Óbidos and Alenquer showed an additional pericentromeric NOR on 8p that was not reported for the population of Belém studied previously. In the karyotypes of 1 male from Curuá and 4 males from Viruá, no terminal NOR was present on 8q, but the pericentromeric NOR on the short arm of this chromosome was always present. The FISH assays mapped the Pep194 repeat to the pericentromeric NOR of chromosome 8 in the specimens from Prainha and Curuá and to the interstitial NOR on chromosome 8 in the specimens from Cedere I. Interestingly, the distal NOR on 8q of specimens from the latter locality was not detected by this probe, suggesting that the dynamics of the repetitive DNA Pep194 might differ between the terminal and interstitial NORs of this karyotype. All of the variations described herein suggest a high level of divergence among the populations currently identified as P. ephippifer. Financial Support: CNPq and FAPESP.