ミトコンドリアDNA解析を基軸にしたヤマビルの進化学的研究

Abstract

The land leech, Haemadipsa, is a terrestrial bloodsucking leech. Haemadipsa leeches are segmented worms belonging to the phylum, Annelida. In Japan, Haemadipsa leeches are found in the forest region between Akita and Okinawa, which is known to be very humid. Haemadipsa leeches are also found in the tropical and subtropical regions of Taiwan, Vietnam, Thailand, and Malaysia. Deer, monkey, and birds serve as host animals for Haemadipsa leeches. These leeches inhabit a wide range of regions owing to the movement of the host animals and due to global warming. Despite the high global abundance of land leeches, their diversity and expansion routes are poorly understood. The distinct morphological differences in Haemadipsa leeches have not been discovered. In this study, mitochondrial DNA (mtDNA) sequences were analyzed to determine the species identity and to evaluate the genetic relationship among Haemadipsa leeches. First the complete mtDNA sequences of several Japanese land leeches were determined. The results revealed 70% sequence similarity—at the amino acid level—with the reference sequences of Megascolecidae and Hirudo nipponia. The tRNA or rRNA sequences of Haemadipsa leeches are unique compared to those of other leeches belonging to the phylum, Annelida. Next, the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene from 10 Haemadipsa leeches in Japan was analyzed and compared with that of land leeches from around the world. Phylogenic analyses for COX1 gene were performed using the neighborjoining method. These results suggest that Haemadipsa leeches have evolved independently and by different mechanisms compared to other leeches.