No abstract

Treefrogs of the genus Pithecopus Cope, 1866 exhibit expressive chromosomal homogeneity which contrasts with a high variation frequency of the nucleolus organizer region (NOR) related to the group. Currently, the genus contains eleven species and no chromosomal data are available on P. palliatus Peters, 1873, P. ayeaye Lutz, 1966 and P. megacephalus Miranda-Ribeiro, 1926. Here, we describe the karyotypes of these three species based on Giemsa staining, C-banding, silver impregnation and in situ hybridization (FISH). We were also analyze the evolutionary dynamic of the NOR-bearing chromosome in species of genus under a phylogenetic view. The results indicate that P. palliatus, P. ayeaye, and P. megacephalus have similar karyotypes, which are typical of the genus Pithecopus. In P. palliatus the NOR was detected in the pericentromeric region of pair 9p whereas in P. ayeaye and P. megacephalus we report cases of the multiple NOR sites in karyotypes. In P. ayeaye the NOR was detected in the pericentromeric region of pair 9p in both homologues and additional sites was detected in pairs 3q, 4p, and 8q, all confirmed by FISH experiments. Already in P. megacephalus the NOR sites were detected in pericentromeric region homologues of pair 8q and additionally in one chromosome of pair 13q. A comparative overview of all the Pithecopus karyotypes analyzed up to now indicates the recurrence of the NOR-bearing chromosome pairs and the position of the NORs sites on these chromosomes. We hypothesized that this feature is a result of a polymorphic condition present in the common ancestor of Pithecopus. In such case, the lineages derived from polymorphic ancestor have reached fixation independently after divergence of lineages, resulting in a high level of homoplasy observed in this marker. Our findings help to fill the gaps in the understanding of the karyotype of the genus Pithecopus and reinforce the role of the evolutionary dynamics of the rDNA genes in karyotype diversification in this group.

No abstract

Anuran genomes have a large number and diversity of transposable elements, but are little explored, mainly in relation to their molecular structure and evolutionary dynamics. Here, we investigated the retrotransposons containing tyrosine recombinase (YR) (order DIRS) in the genome of Xenopus tropicalis and Xenopus laevis. These anurans show 2n = 20 and the 2n = 36 karyotypes, respectively. They diverged about 48 million years ago (mya) and X. laevis had an allotetraploid origin (around 17-18 mya). Our investigation is based on the analysis of the molecular structure and the phylogenetic relationships of 95 DIRS families of Xenopus belonging to DIRS-like and Ngaro-like superfamilies. We were able to identify molecular signatures in the 5' and 3' non-coding terminal regions, preserved open reading frames (ORFs) and conserved domains that are specific to distinguish each superfamily. We recognize two ancient amplification waves of DIRS-like elements that occurred in the ancestor of both species and a higher density of the old/degenerate copies detected in the X. laevis. X. tropicalis showed more recent amplification waves estimated around 16 mya and 3.2 mya and corroborate with high diversity-level of families in this species and with transcriptional activity evidence. Ngaro-like elements presented less diversity and quantity in the genomes, although potentially active copies were also found. Our findings highlight a differential diversity-level and evolutionary dynamics of the YR retrotransposons in the diploid X. tropicalis and X. laevis species expanding our comprehension of the behavior of these elements in both genomes during the diversification process

Treefrogs of the genus Pithecopus Cope, 1866 exhibit expressive chromosomal homogeneity which contrasts with a high variation frequency of the nucleolus organizer region (NOR) related to the group. Currently, the genus contains eleven species and no chromosomal data are available on P. palliatus Peters, 1873, P. ayeaye Lutz, 1966 and P. megacephalus Miranda-Ribeiro, 1926. Here, we describe the karyotypes of these three species based on Giemsa staining, C-banding, silver impregnation and in situ hybridization (FISH). We were also analyze the evolutionary dynamic of the NOR-bearing chromosome in species of genus under a phylogenetic view. The results indicate that P. palliatus, P. ayeaye, and P. megacephalus have similar karyotypes, which are typical of the genus Pithecopus. In P. palliatus the NOR was detected in the pericentromeric region of pair 9p whereas in P. ayeaye and P. megacephalus we report cases of the multiple NOR sites in karyotypes. In P. ayeaye the NOR was detected in the pericentromeric region of pair 9p in both homologues and additional sites was detected in pairs 3q, 4p, and 8q, all confirmed by FISH experiments. Already in P. megacephalus the NOR sites were detected in pericentromeric region homologues of pair 8q and additionally in one chromosome of pair 13q. A comparative overview of all the Pithecopus karyotypes analyzed up to now indicates the recurrence of the NOR-bearing chromosome pairs and the position of the NORs sites on these chromosomes. We hypothesized that this feature is a result of a polymorphic condition present in the common ancestor of Pithecopus. In such case, the lineages derived from polymorphic ancestor have reached fixation independently after divergence of lineages, resulting in a high level of homoplasy observed in this marker. Our findings help to fill the gaps in the understanding of the karyotype of the genus Pithecopus and reinforce the role of the evolutionary dynamics of the rDNA genes in karyotype diversification in this group.

Anuran genomes have a large number and diversity of transposable elements, but are little explored, mainly in relation to their molecular structure and evolutionary dynamics. Here, we investigated the retrotransposons containing tyrosine recombinase (YR) (order DIRS) in the genome of Xenopus tropicalis and Xenopus laevis. These anurans show 2n = 20 and the 2n = 36 karyotypes, respectively. They diverged about 48 million years ago (mya) and X. laevis had an allotetraploid origin (around 17–18 mya). Our investigation is based on the analysis of the molecular structure and the phylogenetic relationships of 95 DIRS families of Xenopus belonging to DIRS-like and Ngaro-like superfamilies. We were able to identify molecular signatures in the 5' and 3' noncoding terminal regions, preserved open reading frames, and conserved domains that are specific to distinguish each superfamily. We recognize two ancient amplification waves of DIRS-like elements that occurred in the ancestor of both species and a higher density of the old/degenerate copies detected in both subgenomes of X. laevis. More recent amplification waves are seen in X. tropicalis (less than 3.2 mya) and X. laevis (around 10 mya) corroborating with transcriptional activity evidence. All DIRS-like families were found in both X. laevis subgenomes, while a few were most represented in the L subgenome. Ngaro-like elements presented less diversity and quantity in X. tropicalis and X. laevis genomes, although potentially active copies were found in both species and this is consistent with a recent amplification wave seen in the evolutionary landscape. Our findings highlight a differential diversity-level and evolutionary dynamics of the YR retrotransposons in X. tropicalis and X. laevis species expanding our comprehension of the behavior of these elements in both genomes during the diversification process.

The inshore area of the Southwestern Atlantic between 22 °S and 29 °S (South Brazilian Bight) is a transitional climatic zone, where the tropical and warm temperate provinces mix. In its northern part, i.e., in the coastal waters of Rio de Janeiro, Brazil, local oceanographic conditions, such as upwelling in the north, and great bays with different degrees of anthropogenic influences in the center and south can determine the population structure of several fish stocks. The Whitemouth croaker (Micropogonias furnieri) is one the most heavily exploited fishing resources in this area, but there are still some doubts about its population structure. In this study, through combined analyses using nuclear genetic markers and morphological and geochemical signatures of otoliths, a divergence of individuals between two populations was identified using microsatellites, while a finer spatial structure with three populations (north, center and south, respectively) was found based on otolith shapes and elemental signatures. This regional population structure may have direct implications for rational fisheries management and conservation of the species.