Chromosome analysis in Pseudopaludicola (Anura, Leiuperidae), with description of sex chromosomes XX/XY in P. saltica.

Taxonomic changes have frequently occurred in the anuran genus Pseudopaludicola as a consequence of high morphological similarity among its species. The present work reports karyotypic analysis of three Pseudopaludicola species sampled in their type locality and four Pseudopaludicola populations from distinct localities, aiming at contributing to the systematics of this genus. Chromosomes were stained with Giemsa or submitted to the silver staining (Ag-NOR) and C-banding techniques. The karyotype was 2n=22 in P. mineira, Pseudopaludicola sp. and two populations of P. saltica. The chromosome pair 8 was heteromorphic in P. saltica, characterizing a XX/XY sex-determination system with telocentric X and submetacentric Y. Highly similar karyotypes with 2n=18 chromosomes were observed in P. canga, P. aff. canga from Barreirinhas, State of Maranhão, Uberlândia, State of Minas Gerais and Icém, State São Paulo. The high similarity among the karyotypes 2n=18 suggested that the populations of P. aff. canga belong to the group 'pusilla', the same group of P. canga. The data demonstrated also that P. aff. canga from Barreirinhas (northeast region) is cytogenetically identical to P. canga with regarding the NOR site position in pair 3 and the presence of a heterochromatic block in the pair 2, whereas P. aff. canga from Uberlândia and Icém (southeast) had the NOR in the pair 9. Moreover, the cytogenetic data discriminated P. mineira and Pseudopaludicola sp. from the previously analyzed species with 22 chromosomes, and suggested that Pseudopaludicola sp. is an undescribed species. Sexual heteromorphic chromosomes are firstly reported in Pseudopaludicola and the data indicated the need of an extensive taxonomic review in this genus.

Chromosomal study of Colostethus brunneus from the type locality and two related species (Anura--Dendrobatidae).

In this paper, we report a chromosomal study of three Brazilian species of Colostethus, C. brunneus from the type locality, Colostethus sp. (aff. trilineatus), and Colostethus sp., which is morphologically similar to C. brunneus. The diploid number for C. brunneus was 2n = 24 chromosomes, in agreement with that previously described for specimens from Peru. Colostethus sp. (aff. trilineatus) and Colostethus sp. showed a very similar karyotype with 22 chromosomes. The NOR was located on pair 3 in C. brunneus, on pair 4 in Colostethus sp. (aff. trilineatus), and on pair 2 in Colostethus sp. In one specimen of Colostethus sp., an additional NOR site was located on pair 7 in only one of the homologs. This extra Ag-NOR site was confirmed by FISH using an rDNA probe. In addition to the NOR location, the C-banding pattern was also species-specific, despite the similar chromosomal morphology of the species. These results indicate that although these species may be closely related, there is a clear dichotomy in their chromosome number.

Cytogenetic analysis of four central Amazonian species of Colostethus (Anura - Dendrobatidae) with a diploid complement of 22 chromosomes.

Colostethus marchesianus from the type locality and three related species had 2n = 22 chromosomes, which differed from most other Colostethus species that have 2n = 24 chromosomes. The species analyzed were morphologically similar and showed a conservative karyotype, although they could be distinguished from each other by their C-banding pattern. Additional NOR sites, heteromorphism in NOR size and heterochromatin, and an additional rDNA site detected by FISH, were observed. These data suggest that chromosomal rearrangements and hetrochromatin-related events may have contributed to the karyotype differentiation of these Colostethus.