Coloration pattern in populations of the eastern medicinal leech, Hirudo orientalis Utevsky & Trontelj, 2005 (Clitellata, Hirudinida): geographical distribution and life history

Populations of the eastern medicinal leech, Hirudo orientalis from 13 localities at six freshwater eco-regions from Kazakhstan, Uzbekistan, Azerbaijan and Iran were analyzed for coloration pattern variability. In addition, coloration patterns of 1017 reared specimens including hatched, juvenile and adult leeches were considered. Elements of coloration pattern including dorsal paramarginal, paramedian and lateral stripes and ventral pattern variations were chosen as the basis of comparative population analysis. Data analyses revealed a strong association of the dorsal paramarginal stripe with other dorsal elements. The dominant morphotype remained stable from hatchlings to older individuals, and coloration traits seem to be inheritable. A sufficient monomorphy of dorsal elements of the coloration pattern was recorded in most localities suggesting potential signs of genetic drift. On a larger geographical scale, populations of the western Caspian Sea (Azerbaijan) differ from all other localities (Central Asia and Iran) in their pattern variation. The high morphotype diversity in the populations of southern distribution ranges, especially southern Caspian Sea, could suggest that the area is a probable historical refugium for the species.