Cytogenetic and molecular characteristics of Potamotrygon motoro and Potamotrygon sp. (Chondrichthyes, Myliobatiformes, Potamotrygonidae) from the Amazon basin: Implications for the taxonomy of the genus.

The chromosomes of two freshwater stingrays, Potamotrygon motoro and Potamotrygon sp., from the Amazon River basin in Brazil were investigated using integrated molecular (cytochrome c oxidase subunit 1) and cytogenetic analyses. Potamotrygon motoro presented intraspecific variation in the diploid number, with 2n=66 in the females and 2n=65 in the males, while Potamotrygon sp. had a karyotype with 66 chromosomes, in both sexes. The C-banding revealed the presence of heterochromatic blocks accumulated in the centromeric region of all the chromosomes in both species. The FISH assays with 18S DNA probes highlighted the terminal region of three or four chromosome pairs in P. motoro and seven chromosomes in Potamotrygon sp. The rDNA 5S sequences were found in only one chromosomal pair in both species. The interspecific genetic distance based on the COI sequences, between P. motoro and Potamotrygon sp. from Amazon River was 10.8%, while that between the Amazonian P. motoro and Potamotrygon amandae from the Paraná River was 2.2%, and the genetic distance between Potamotrygon sp. and P. amandae was 11.8%. In addition to the new insights on the cytogenetics of the study species, the results of the present study confirmed the existence of heteromorphic sex-linked chromosomes in P. motoro.

Molecular identification of Brachygenys and Haemulon species (Perciformes: Haemulidae) from the Brazilian coast

The fishes of the Haemulidae family are currently allocated to 19 genera with a worldwide distribution in the tropical and subtropical waters of the world's oceans. Brachygenys and Haemulon are important genera of reef fish in Brazil, as they occur in large shoals, which are both ecologically and commercially valuable. This study identified the Brazilian species of the genera Brachygenys and Haemulon using DNA barcodes. While we found only a single lineage in Brachygenys chrysargyrea, Haemulon melanurum, H. parra, and H. squamipinna, more than one molecular operational taxonomic unit (MOTU) was identified in H. atlanticus, H. aurolineatum, and H. plumieri, indicating the possible existence of discrete populations or cryptic species.(AU)

Os peixes da família Haemulidae estão atualmente distribuídos em 19 gêneros, com distribuição mundial em águas oceânicas tropicais e subtropicais. Brachygenys e Haemulon são importantes gêneros de peixes recifais do Brasil, visto que ocorrem em grandes cardumes, de valores ecológicos e comerciais. Este estudo identificou as espécies brasileiras dos gêneros Brachygenys e Haemulon usando o código de barras de DNA. Embora apenas uma única linhagem de Brachygenys chrysargyrea, Haemulon melanurum, H. parra e H. squamipinna tenha sido encontrada em nosso conjunto de dados, mais de uma unidade taxonômica operacional molecular (MOTU) foi identificada em H. atlanticus, H. aurolineatum e H. plumieri, indicando a possível existência de populações discretas ou espécies crípticas.(AU)

Karyotype description and evidence of multiple sex chromosome system X1X1X2X2/X1X2Y in Potamotrygon aff. motoro and P. falkneri (Chondrichthyes: Potamotrygonidae) in the upper Paraná River basin, Brazil

Análises citogenéticas de Potamotrygon aff. motoro e P. falkneri identificaram a ocorrência de um sistema múltiplo de cromossomos sexuais do tipo X1X1X2X2/X1X2Y, em ambas as espécies, com 2n = 66 cromossomos em fêmeas e 2n = 65 cromossomos nos machos. As regiões organizadoras de nucléolos (RONs) identificadas pela reação Ag-RON, evidenciaram marcações múltiplas em ambas as espécies (com variações de 5 a 7 RONs). A técnica de bandamento C, revelou a presença de blocos heterocromáticos localizados nas regiões centromérica em quase todos os cromossomos nas duas espécies em estudo. Através do presente estudo foi evidenciada uma heterogeneidade nos cariótipos, permitindo sugerir que rearranjos cromossômicos, como inversões e/ou translocações, ocorreram durante a evolução cromossômica nas duas espécies desse gênero.

Cytogenetic analysis of Potamotrygon aff. motoro and P. falkneri indicated the occurrence of an X1X1X2X2/X1X2Y multiple sex chromosome system in both species, with 2n = 66 chromosomes for females and 2n = 65 chromosomes for males. The nucleolus organizer regions (NORs) identified using Ag-NOR technique showed that both species have multiple Ag-NORs (5 to 7 chromosomes stained). C-banding technique indicated the presence of heterochromatic blocks in the centromeric regions of almost all chromosomes in both species. Through this study there was evidence of heterogeneity in the karyotypes, which suggests that chromosomal rearrangements such as inversions and/or translocations occurred during the chromosomal evolution in two species of this genus.