Cocoon from medicinal leech Hirudo verbena

Photomacrograph of a cocoon from the medicinal leech Hirudo verbana. Leeches are hermaphrodites and have both a male and a female genital organ. They lay fertilised eggs into a cocoon which nourishes and protects the eggs as they develop. Leeches are aquatic, blood sucking, segmented worms, which mainly feed on mammalian blood. In a single feed they can consume over 3 times their body weight in blood. There are several species of medicinal leech which are used in medicine today to help re-establish blood flow to skin grafts and to reattached body parts. Leech saliva contains many proteins which have anti-coagulant, anti-inflammatory, vasodilating and anaesthetic properties. Historically leeches were used for blood letting in order to balance the humours of the body. Width of image is 2 cm.