Two new leech species of the genus Haemadipsa Tennent, 1859 from Tibet, China and characterization of their mitochondrial genomes (Clitellata: Hirudiniformes: Haemadipsidae)

This paper presents two novel terrestrial leech species, Haemadipsa nigrilineata sp. nov. and Haemadipsa medogensis sp. nov., collected from forested regions in Tibet, China. On the basis of morphological observations, mitogenomic sequence analysis and the mitochondrial COI gene sequence phylogenetic inference, both species are herein described as new within the genus Haemadipsa Tennent, (Haemadipsidae). These two species are in line with the general diagnosis of the genus Haemadipsa in terms of living environment, annulation pattern, having five pairs of eyespots, and the position of the gonopores (XI b5/b6 and XII b5/b6).

The diagnostic features for the new species include: Haemadipsa nigrilineata sp. nov. possesses a continuous jet-black longitudinal stripe along the dorsal midline and has a vaginal sac large and quadrate; Haemadipsa medogensis sp. nov. exhibits scattered irregular patterns on the dorsum and the vaginal sac is significantly large, being two to three times as long as it is wide, and the epididymis presents a dagger-like shape.

Complete mitogenome sequencing revealed circular genomes of 14,755 bp for Haemadipsa nigrilineata sp. nov. and 14,892 bp for Haemadipsa medogensis sp. nov. Both genomes exhibit canonical invertebrate mitochondrial architecture, including 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), 2 ribosomal RNAs (rRNAs), and a non-coding control region. The phylogenetic analysis based on the mitochondrial genome showed that Haemadipsa medogensis sp. nov. is sister to H. crenata while Haemadipsa nigrilineata sp. nov. forms an independent lineage sister to H. hainana, H. yanyuanensis, Haemadipsa medogensis sp. nov. and H. crenata.