Cytogenomics of Myloplus tiete reveals conserved satellite DNAs since the Late Eocene in Serrasalmidae (Teleostei, Characiformes)

The Neotropical family Serrasalmidae (pacus and piranhas) exhibits remarkable karyotype conservation, yet cytogenetic data remain limited for several genera, particularly Myloplus. Here we present the first integrative cytogenomic characterization of Myloplus tiete, an endemic and near-threatened species from the upper Paraná River basin, combining classical cytogenetics with satellitome analysis. Karyotyping of 12 specimens collected from Rio Grande, Frutal-MG, Brazil, revealed a consistent diploid number of 2n = 58 chromosomes with karyotype formula 16m + 20sm + 22a, while C-banding identified heterochromatic blocks predominantly in pericentromeric and subtelomeric regions. Genome sequencing and iterative satDNA mining identified 32 satellite DNA families, with repeat lengths ranging from 24 to 2,265 bp and a predominance of AT-rich sequences. Comparative analysis with the Colossomatinae species Colossoma macropomum and Piaractus mesopotamicus revealed 12 conserved satDNAs across ~ 40 million years of divergence, with moderate consensus turnover rates. FISH mapping of the ten most abundant satDNAs revealed diverse chromosomal distributions, including pericentromeric, subtelomeric, and dispersed patterns, highlighting the diverse genomic integration of conserved repeats. These findings provide evidence for long-term evolutionary conservation of both karyotype architecture and satDNA repertoires across Serrasalmidae subfamilies and suggest that structural or functional constraints may contribute to shaping the evolution of repetitive DNA in this ecologically and aquaculturally important fish group.