The role of satellite DNAs in the chromosomal rearrangements and the evolution of the rare XY1Y2 sex system in Harttia (Siluriformes: Loricariidae).

The underlying processes behind the formation, evolution, and long-term maintenance of multiple sex chromosomes have been largely neglected. Among vertebrates, fishes represent the group with the highest diversity of multiple sex chromosome systems and, with six instances, the Neotropical fish genus Harttia stands out by presenting the most remarkable diversity. However, although the origin mechanism of their sex chromosome systems is well discussed, little is known about the importance of some repetitive DNA classes in the differentiation of multiple systems.

Repetitive DNAs and chromosome evolution in Megaleporinus obtusidens and M. reinhardti (Characiformes: Anostomidae).

The high dynamism of repetitive DNAs is a major driver of chromosome evolution. In particular, the accumulation of repetitive DNA sequences has been reported as part of the differentiation of sex-specific chromosomes. In turn, the fish species of the genus Megaleporinus are a monophyletic clade in which the presence of differentiated ZZ/ZW sex chromosomes represents a synapomorphic condition, thus serving as a suitable model to evaluate the dynamic evolution of repetitive DNA classes.

Homeology of sex chromosomes in Amazonian Harttia armored catfishes supports the X-fission hypothesis for the XXY sex chromosome system origin.

The Neotropical monophyletic catfish genus Harttia represents an excellent model to study karyotype and sex chromosome evolution in teleosts. Its species split into three phylogenetic clades distributed along the Brazilian territory and they differ widely in karyotype traits, including the presence of standard or multiple sex chromosome systems in some members. Here, we investigate the chromosomal rearrangements and associated synteny blocks involved in the origin of a multiple XXY sex chromosome system present in three out of six sampled Amazonian-clade species.