Abstract Taxonomic and cytogenetic aspects of Proceratophrys have not been thoroughly clarified in the literature; thus, the objective of the present study was to provide unprecedent karyotype data regarding P. schirchi, P. laticeps and P. melanopogon. Additionally, the karyotype of P. boiei (2n = 22) and its ZZ / ZW sex chromosome system was analyzed for different populations of southeastern and southern Brazil. All Proceratophrys species have a diploid number of 2n = 22 chromosomes. In P. schirchi, a strong C-band was found in the long arm in one of the homologues of the pair 8 in female metaphasic cells, denoting that this chromosome pair could represent the heteromorphic sex chromosome in a ZZ / ZW sex system. Despite the conserved number of chromosomes, there are considerable chromosomal differences in P. melanopogon and P. boiei (southern Brazil), strongly differentiating them cytogenetically from other species of the genus. Moreover, with the confirmation of chromosomal heteromorphism related to sexual differentiation in P. boiei and the possible description of this system in P. schirchi, the Proceratophrys genus can be regarded as an interesting group for evolutionary studies and sex chromosome differentiation in anurans.

RESUMO A localização cromossômica dos genes de RNAr 5S e RNAsn U2 de Piabina argentea, Piabarchus stramineus e duas espécies de Bryconamericus provenientes de duas bacias hidrográficas foi investigada, com a intenção de contribuir com o entendimento de características evolutivas destes DNAs repetitivos na subfamília Stevardiinae. O número cromossômico diploide foi 2n = 52 para Bryconamericus cf. iheringii, Bryconamericus turiuba, Piabarchus stramineus e Piabina argentea. Os sítios de DNAr 5S foram localizados em um par cromossômico em P. stramineus e B. cf. iheringii, e em dois pares em B. turiuba e P. argentea. Os sítios de DNAsn U2 foram localizados em um par em todas as espécies. Experimentos de FISH com duas sondas mostraram que a co-localização entre os DNAr 5S e DNAsn U2 em P. stramineus pode representar um marcador para esta espécie. Portanto, o presente estudo demonstrou que o número de sítios de DNAsn U2 observado para as quatro espécies foi conservado, porém características particulares podem ser encontradas no genoma de cada espécie.

ABSTRACT The chromosomal location of 5S rRNA and U2 snRNA genes of Piabina argentea, Piabarchus stramineus and two Bryconamericus species from two different Brazilian river basins were investigated, in order to contribute to the understanding of evolutionary characteristics of these repetitive DNAs in the subfamily Stevardiinae. The diploid chromosome number was 2n = 52 for Bryconamericus cf. iheringii, Bryconamericus turiuba, Piabarchus stramineus and Piabina argentea. The 5S rDNA clusters were located on one chromosome pair in P. stramineus and B. cf. iheringii, and on two pairs in B. turiuba and P. argentea. The U2 snDNA clusters were located on the one pair in all species. Two-color FISH experiments showed that the co-localization between 5S rDNA and U2 snDNA in P. stramineus can represent a marker for this species. Thus, the present study demonstrated that the number of U2 snDNA clusters observed for the four species was conserved, but particular characteristics can be found in the genome of each species.

The blow flies Chrysomya putoria and C. megacephala have 2n=12 chromosomes, five metacentric pairs of autosomes and an XX/XY sex chromosome pair. There are no substantial differences in the karyotype morphology of these two species, except for the X chromosome which is subtelocentric in C. megacephala and metacentric in C. putoria and is about 1.4 times longer in C. putoria. All autosomes were characterized by the presence of a C band in the pericentromeric region; C. putoria also has an interstitial band in pair III. The sex chromosomes of both species were heterochromatic, except for a small region at the end of the long arm of the X chromosome. Ribosomal genes were detected in meiotic chromosomes by FISH and in both species the NOR was located on the sex chromosomes. These results confirm that C. putoria was the species introduced into Brazil in 1970s, and not C. chloropyga as formerly described.