Comparative genomics of three non-hematophagous leeches (Whitmania spp.): focusing on antithrombotic genes

Leeches are well known for their blood-feeding habits and are widely used for medicinal purposes as they secrete various antithrombotic substances. However, some leeches such as Whitmania spp. exhibit non-hematophagous feeding habits and their significance for medicinal use is debated. In this study, we provide chromosome-level genomes of two non-hematophagous leeches Whitmania acranulata and Whitmania laevis, and combined with our previous results of Whitmania pigra, we systematically analyzed the similarities and differences on the genomes and especially their antithrombotic genes among the three non-hematophagous Whitmania leeches. For W. acranulata, W. laevis, and W. pigra, the genome size (181.72 Mb, 173.87 Mb, and 173.56), the percentage of repeat sites (29.55%, 28.28%, and 27.02%), and the number of protein-coding genes (27,068, 23,805, and 24,156) were close to each other, respectively. In contrast, both the total number of the antithrombotic genes (100, 63, and 79), and the detailed constitutes of different antithrombotic gene families were obviously different among the three leeches. There were also massive genetic variations among the members within each antithrombotic gene/protein family. RNA-Seq-based gene expression estimation showed that the expression profiles of the antithrombotic gene families were apparently different among the three leeches. This is the most comprehensive comparison of the genomes and antithrombic biomacromolecules for the Whitmania leeches to date. Our results will greatly facilitate the evolutionary research and application of leech derivatives for medical and pharmaceutical purposes of thrombosis.