Comparative Genomics Unveils Unique Antithrombotic Gene Expansion in Haemadipsa yanyuanensis

Abstract Haemadipsa yanyuanensis is a terrestrial blood-feeding leech with underexplored anticoagulant adaptations. Here, we present its first chromosome-level genome assembly (165.32 Mb, 9 chromosomes; BUSCO completeness: 97.6%) generated using Nanopore, Hi-C, and RNA-seq data. We identified 193 antithrombotic genes across 15 families, representing a 2.2- to 2.7-fold increase in gene number but a reduction in gene family diversity compared to aquatic medicinal leeches (Hirudo medicinalis, Hirudinaria manillensis, and Hirudo nipponia). Notably, bdellin, LDTI, and LCI gene families exhibited large-scale expansions ranging from 8.7- to 25-fold compared to aquatic leeches. while the progranulin gene exhibited a lineage-specific structure with 122 cysteine residues and nine tandem repeats. Transcriptomic profiling revealed high expression of these expanded families, suggesting their pivotal role in terrestrial blood-feeding adaptation. Our study reveals a novel gene family expansion-contraction model for antithrombotic evolution. These unique genomic data provide a new resource for the development of next-generation anticoagulant drugs.