ANATOMY OF LEECHES
Medical leeches have an remarkable unique anatomy. The body has been flattened typically in dorso-ventral direction. Segments have been transformed into sucking discs in anterior and posterior ends. The anterior sucking disc is generally smaller than the posterior one, and mouth is surrounded by this disc. The posterior sucking disc is formed by eight segments merged in the form of a disc. The body always consists of 34 segments. The second-order external rings are hidden by the main segments. It has no seta. Clitella are located on segments 9, 10 and 11 of leeches, and this area is called the clitellar area. The clitellar area bears one male and one female reproductive hole. The mid-part of the body contains 15 segments. This is the largest part of the body (between the segments 12 and 26). (Davies, 1991; Barnes, 1974; Kaestner, 1967; Sawyer, 1986).