[PROVISIONAL] Chromosomal characterization of Amazonian freshwater stingrays with evidence for new karyomorphs and XX/XY sex chromosomes

Abstract

Abstract Cytogenetic studies in the subfamily Potamotrygoninae has already provided valuable insights into the understanding of the evolution and diversification of its species. In the present study, the chromosomal features of seven nominal potamotrygonin species are provided: Plesiotrygon iwamae (2n=74, FN=120), Potamotrygon amazona (2n=66, FN=107), P. constellata (2n=66, FN=110), P. leopoldi (2n=64, FN=102), P. motoro (2n=66, FN=106) from four different localities, P. orbignyi (2n=66, NF=106), Potamotrygon scobina (2n=66, FN=104), from Central Amazon. Additionally, we found new karyomorph in P. wallacei. We considered the localization of Nucleolus Organizer Regions (NORs), as well as the pattern of constitutive heterochromatin, as species-specific characters. We found an XX/XY sex chromosome system in P. orbignyi, and we suggest that P. scobina and P. amazona also possess the same sex chromosome system. Overall, the chromosomal evolution in this group appears to have progressed toward a reduction in the diploid number, with a concomitant increase in the number of bi-armed and nucleolar chromosomes.

Keywords

• Elasmobranchs
• cytogenetics
• chromosomal rearrangements
• sex chromosomes
• karyotypic diversity