Cytogenetics of Neotropical fishes: Patterns, advances and prospects after five decades of research.

This review synthesizes the most significant advances and innovations in the cytogenetic study of Neotropical fishes, with emphasis on recurrent chromosomal patterns, evolutionary mechanisms, and the integration of modern genomic tools. The Neotropical region, which harbors more than 12,000 fish species, exhibits not only extraordinary taxonomic richness but also remarkable chromosomal diversity. Chromosomal rearrangements have been associated with speciation and ecological adaptation in both freshwater and marine lineages. Modern techniques, including fluorescence in situ hybridization, chromosome painting, and comparative genomic hybridization (CGH), have substantially improved our ability to resolve morphologically indistinguishable species and clarify their evolutionary relationships. When integrated with phylogenetic and genomic approaches, cytogenetics becomes a robust framework for exploring biodiversity and chromosomal evolution within the complex Neotropical fauna. Despite these advances, substantial challenges remain, particularly the scarcity of cytogenetic data for many taxa and regions. Future research, driven by high-throughput genomic technologies, is expected to deepen our understanding of chromosomal evolution and to support conservation efforts for this rich but increasingly threatened fish fauna.