Divergence in the chromosomal distribution of repetitive sequences in Neotropical cichlid species of the genus Lugubria

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Abstract
Cytogenetic studies provide valuable insights into the evolutionary dynamics of fish genomes, particularly in groups with high species diversity and ecological relevance. Among Neotropical cichlids, chromosomal data have revealed both conservation patterns and significant structural variations, reflecting intense karyotypic diversification. In this context, mapping repetitive DNA sequences has proven useful in aiding understanding of genomic organization and chromosomal evolution. However, information remains scarce for several cichlid genera. The present study investigated the chromosomal distribution of repetitive sequences, such as 18S and 5S ribosomal genes, as well as telomeric sequences, in three Amazonian species of Lugubria: L. cincta, L. strigata, and L. lugubris. The results revealed a diploid number of 2n = 48, along with variations in the karyotypic formula among the species. Mapping of repetitive sequences revealed distinct patterns of 18S rDNA distribution, with clusters located on different chromosome pairs. Conversely, the 5S rDNA showed a conserved position on a subtelocentric/acrocentric pair in all three species. Furthermore, the presence of interstitial telomeric sequences in L. cincta and L. strigata indicates greater genomic plasticity in these species, suggesting more pronounced chromosome dynamics in the genus Lugubria. These data contribute to the understanding of chromosomal evolution and diversification in this diverse group of Neotropical cichlids and may aid in future cytotaxonomic studies.

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