Additional file 1: Supplementary figure S1 and S2. Figure S1. GenomeScope Analysis of the 23-mers for W. Pigra genome sequencing data. Estimate of the heterozygous portion is 0.765%. The estimated genome size of W. Pigra was ~ 162 Mbp. Figure S2. The heatmap displays the pairwise similarities values among the Hirudin sequences in Fig. 4. The Hirudin sequences belong to G1, G2, G3, respectively. Within the group, the pairwise similarities of Hirudins are more than 60%. In contrast, in different groups, the pairwise similarities of Hirudins are between 30 and 60%. Whether between G2 and G1 or between G3 and G1, the pairwise similarities are always below 60%.