Telomere-to-telomere gap-free genome assembly of the Opsariichthys evolans (Cypriniformes: Cyprinidae)

Opsariichthys evolans is a stream-dwelling fish species endemic to China, with its primary distribution encompassing southeastern China and Taiwan. Initially classified under the genus Zacco, it was later reclassified into the genus Opsariichthys based primarily on mitochondrial DNA evidence. However, this taxonomic revision remains partially inconclusive due to the absence of whole-genome data. Therefore, we assembled a telomere-to-telomere, gap-free genome assembly of O. evolans, consisting of 39 chromosomes with one contiguous sequence per chromosome. The assembly had a total size of 886.9 Mb and a contig N50 of 25.44 Mb. The presence of the telomere repeat was clearly confirmed in the genome. BUSCO assessment confirmed 99.34% genome completeness. Collinearity analysis revealed high synteny between O. evolans, O. bidens and Zacco platypus. Genomic comparisons revealed key candidate genes and related biological pathways potentially responsible for color patterning and hydrodynamic adaptation. The complete O. evolans genome provides insights into its genome structure and function, and supports the taxonomic reclassification between the genera Opsariichthys and Zacco.