Comparative analysis reveals highly conserved satellite DNA landscapes in two sympatric Gymnotus (Teleostei, Gymnotiformes) electric knifefish

Significant structural and evolutionary aspects associated with satellite DNAs (satDNAs) have been uncovered through the combination of cytogenetic and genomic analysis in a wide variety of organisms. In the last few years, several complete catalogs of satDNAs (the so-called satellitomes) were characterized in fishes, and despite the presence of comparative analysis in Neotropical fishes, the order Gymnotiformes remains largely unexplored. Thus, this study aimed to present a comparative satellitome analysis for weakly electric fishes by investigating the richness of satDNA sequences in the genomes of two banded knifefishes: Gymnotus cuia and Gymnotus sylvius. Our investigations identified 72 and 66 satDNA families in G. cuia and G. sylvius, respectively, characterized by varied motif genomic expansion and a high abundance of monomers in both species. The comparative study revealed a widely shared satDNA library, identifying 40 pairwise correspondences of satDNA sequences among the species, exhibiting varied levels of sequence similarity. The chromosomal mapping of the main sequences common to the catalogs facilitated inferences regarding the structural dynamics of satDNA accumulation and distribution throughout Gymnotus. Furthermore, we incorporated a species identification method utilizing quick-FISH of GcuSat07|GSySat05, thereby facilitating the identification of these species. Our data demonstrate significant satDNA sharing between these species, reflecting the recent divergence between these two species.