[Sequence analysis of rDNA-ITS gene in medicinal leeches and their closely related species (Euhirudinea:Arhynchobdellida)]

To explore the phylogenetic relationships among medicinal leeches and their closely related species by comparing their ITS gene fragments.

8 different leech species, including Whitmania pigra, Whitmania acranulata, Whitmania laevis, Hirudo nipponia, Poecilobdella manillensis, Poecilobdella javanica, Poecilobdella hubeiensis and Erpobdella octoculata were collected as the materials for study. After the total DNA of all samples was extracted, amplified by PCR and cloned, their ITS sequence, AT content, variable sites and evolutionary relationships were analyzed.

The length of ITS was 948-981 bp with 210 variable sites and 43 inserts on/deletion. The average G + C content was high up to 56.0%-57.8%. The aligned ITS sequence demonstrated that their ITS genes were relatively conserved in species. Data analysis showed that the relationship between E. octoculata and P. javanica was closer than others, their genetic distance was only 0.007. Through the phylogenetic tree analysis, three species of Haemopidae and four species of Hirudinidae were obviously clustered into two branches.

The results support the taxonomic status of Haemopidae and Hirudinidae, and provide sufficient evidences that Erpobdella octoculata and Poecilobdella javanica should not be assigned to two genera, of which the taxonomic system should be further researched.