A complete telomere-to-telomere chromosome-level genome assembly of X-ray tetra (Pristella maxillaris).

X-ray tetra (Pristella maxillaris) originates from the lower Amazon basin in South America. It is renowned for its strikingly transparent body, which has drawn significant interests in biomedical research and the world ornamental fish industry. Nevertheless, genomic resources for this interesting fish species remains scarce, hindering exploration of the molecular basis behind its unique transparency. To address this gap, we constructed the first complete telomere-to-telomere (T2T) chromosome-scale genome assembly of the X-ray tetra by integration of PacBio HiFi, ONT ultra-long, and Hi-C sequencing technologies. This haplotypic assembly spans approximately 1.1 Gb, with a contig N50 of 42.8 Mb. It is anchored onto 25 chromosomes, highlighting a complete set of 50 telomeres and 25 centromeres. We predicted 514.3 Mb of repetitive sequences and annotated 28,456 protein-coding genes in the assembled genome. Subsequent BUSCO analysis discovered high genome completeness (98.0%). This high-quality T2T genome assembly provides a valuable genetic resource for investigating the molecular mechanisms underlying transparency, and supporting in-depth studies on functional genomics, genetic diversity, and selective breeding for this economically important species.