A chromosome-level, gap-free genome assembly of the fish parasite Trypanosoma larimichthysi from large yellow croaker.

Chromosome-level genome assembly of the bitterling Rhodeus sinensis (Acheilognathidae) reveals genomic signatures associated with its mussel-dependent reproductive system.

Bitterlings (Acheilognathidae) exhibit a unique reproductive strategy characterized by symbiotic embryonic development inside the gill cavities of freshwater unionid mussels. Despite extensive ecological and physiological research on this system, genomic resources for bitterlings have remained limited, hindering comparative and evolutionary studies. Here, we present a high-quality, chromosome-level genome assembly for Rhodeus sinensis, a widely distributed bitterling species in the Korean Peninsula. By combining PacBio Continuous Long Read (CLR) sequencing, Illumina short reads, and Hi-C scaffolding, we generated a 0.77 Gb genome assembly with a scaffold N50 of 30.06 Mb. The final assembly comprises 24 chromosome-scale scaffolds, accounting for 98.3% of the assembled genome, with a BUSCO completeness score of 96.3% against the Actinopterygii_odb10. Comparative genomic analyses identified prominent expansions in gene families associated with alcohol metabolism, lipid catabolism, and oxidative stress responses. These genomic signatures of metabolic rewiring suggest a potential fuel flexibility, which may serve as a critical adaptive mechanism to mitigate the severe hypoxic stress encountered within the host mussel's gill environment. Ultimately, our chromosome-level genome assembly and findings provide a robust genomic foundation, contributing to a deeper understanding of the extreme physiological adaptations and unique life-history evolution within the Acheilognathidae.

A chromosome-scale Plasmodium cynomolgi Berok genome reveals a distinct subtelomeric architecture and a highly diverged primate malaria lineage

A gap-free, telomere-to-telomere chromosome-scale genome assembly of the mangrove red snapper, Lutjanus argentimaculatus

The mangrove red snapper (Lutjanus argentimaculatus) is a commercially important marine fish species in the Indo-Pacific region. Despite its significant economic value for aquaculture, existing genomic resources remain fragmented, limiting the advancement of molecular breeding and functional genomic studies. Here, we present a gap-free, telomere-to-telomere (T2T) genome assembly of L. argentimaculatus, generated using a hybrid approach combining PacBio HiFi, Oxford Nanopore ultra-long reads and Hi-C technology. The resulting assembly comprises exactly 24 scaffolds spanning 1.03 Gb, perfectly matching the haploid chromosome number with a contig N50 of 46.17 Mb. Notably, this assembly resolves all physical gaps present in previous versions, achieving a BUSCO completeness score of 98.2%. Comprehensive genome annotation successfully predicted 23,167 protein-coding genes. Among these, 22,067 genes (95.25%) were functionally annotated across major public databases, including eggNOG, InterPro, and Swiss-Prot. Furthermore, structural analysis successfully identified 19 telomeres and 20 centromeres, validating the chromosomal integrity. This high-fidelity, gap-free reference genome provides a robust foundation for comparative genomics, population genetics, and the genetic improvement of Lutjanidae species.

Chromosome-level genome assembly of the cyprinid fish Onychostoma lini using PacBio HiFi and Hi-C sequencing

Onychostoma lini is an ecologically and economically important cyprinid species endemic to the mountain rivers of southern China. Wild populations have sharply declined due to habitat fragmentation, hydropower development, and overexploitation, yet genomic information remains unavailable, hindering studies on its diversity, adaptation, and conservation. Here, we assembled the first chromosome-level genome of O. lini using PacBio HiFi long-read sequencing, Illumina short-read polishing, and Hi-C scaffolding. The 907.5 Mb assembly achieved a contig N50 of 32.83 Mb and a scaffold N50 of 34.89 Mb, with 99.93% of sequences anchored to 25 chromosomes. Repetitive elements occupied 387.36 Mb, representing 42.69% of the genome. We predicted 28,597 protein-coding genes, 99.05% of which were functionally annotated in NR, KEGG, InterPro, SwissProt, and GO databases. BUSCO analysis identified 97.9% complete orthologs, confirming assembly completeness and annotation accuracy. This high-quality reference genome provides a foundational resource for investigating cyprinid evolution, environmental adaptation, and molecular breeding, and supports the conservation of O. lini .

Chromosome-Level Genome of Simulium vittatum Links Black Fly Cytogenetics to Genome Organization and Evolution

Black flies (Diptera: Simuliidae) are important vectors of pathogens affecting human and animal health, yet the absence of a chromosome-level nuclear reference genome has constrained molecular and evolutionary studies of the family. Here, we present the first chromosome-level nuclear genome and a developmental transcriptomic resource for the long-established IS-7 laboratory lineage of Simulium vittatum. Combining Oxford Nanopore long-read sequencing with Hi-C scaffolding, we assembled a 340.4-Mb genome, with 99.1% of the assembly resolved into three chromosome-length scaffolds (N50=104.8 Mb, BUSCO completeness 93.9%), consistent with the known 2n = 6 karyotype. Using the historically mapped molecular landmarks SVAT and SVEP, we assigned the two arms of chromosome III as IIIS and IIIL, respectively, linking sequence coordinates to the classical polytene chromosome map. Repetitive DNA comprises 46.48% of the assembly, including 29.68% unclassified repeats, and annotation identified 14,732 protein-coding genes and 16,417 transcripts. This reference genome connects classical black fly cytogenetics with sequence-level analyses of genome organization, structural variation, and gene content, addressing a major genomic gap within Culicomorpha and providing a foundation for comparative studies of chromosome evolution, hematophagy, and vector biology across Simuliidae.

Near telomere-to-telomere genome assembly of the rainbow trout (Oncorhynchus mykiss)

The rainbow trout (Oncorhynchus mykiss) exhibits extensive karyotypic diversity (2n = 58–64) driven by Robertsonian translocations, yet widely used reference genomes are derived from North American lineages, leaving Chinese aquaculture populations underrepresented. Here, we present a near telomere-to-telomere (T2T) genome assembly of a farmed rainbow trout from China. Integrating PacBio HiFi, ONT ultra-long reads, and Hi-C data, we assembled a 2.29 Gb genome with 99.04% anchored to 30 chromosomes. Notably, the genome contains only 18 gaps, with 16 gap-free chromosomes and 13 achieving T2T status. Comparative synteny analysis revealed a third chromosomal fission/fusion iteration in which Swanson Omy14 splits into Arlee Omy14 and Omy32. Annotation identified 43,137 protein-coding genes, with a BUSCO completeness of 98.9%. This dataset provides a valuable resource for resolving lineage-specific structural variation, supporting pangenome construction and facilitating molecular breeding in rainbow trout.