Genomic signatures associated with recurrent scale loss in cyprinid fish

Abstract

AbstractScale morphology represents a fundamental feature of fish and a key evolutionary trait underlying fish diversification. Despite frequent and recurrent scale loss throughout fish diversification, comprehensive genome‐wide analyses of the genomic signatures associated with scale loss in divergent fish lineages remain scarce. In the current study, we investigated genome‐wide signatures, specifically convergent protein‐coding gene loss, amino acid substitutions, and cis‐regulatory sequence changes, associated with recurrent scale loss in two divergent Cypriniformes lineages based on large‐scale genomic, transcriptomic, and epigenetic data. Results demonstrated convergent changes in many genes related to scale formation in divergent scaleless fish lineages, including loss of P/Q‐rich scpp genes (e.g. scpp6 and scpp7), accelerated evolution of non‐coding elements adjacent to the fgf and fgfr genes, and convergent amino acid changes in genes (e.g. snap29) under relaxed selection. Collectively, these findings highlight the existence of a shared genetic architecture underlying recurrent scale loss in divergent fish lineages, suggesting that evolutionary outcomes may be genetically repeatable and predictable in the convergence of scale loss in fish.