PAR: Leeches

This unit is based on the genetic formation of Leeches



Biology (Characteristic Features)

biology of leeches

Leeches are dorso-ventrally flattened and segmented worms, with anterior and posterior suckers present for attachment to host and movement. Leeches are ectoparasitic, hence all organ systems are well developed. Their suckers are for attachement to their host during blood meal. Leeches are able to display a variety of behaviors that allow them to explore their environments and feed on their hosts. Exploratory behavior includes head movements and body waving

Most leeches do not feed on human blood, but instead prey on small invertebrates, which they eat whole. To feed on their hosts, leeches use their anterior suckers to connect to hosts for feeding, and also release an anesthetic to prevent the hosts from feeling them. Once attached, leeches use a combination of mucus and suction to stay attached and secrete an anticoagulant enzyme,hirudin, into the hosts’ blood streams. Though certain species of leeches feed on blood, not all species can bite;

Life Cycle

life cycle of leech

Members are hermaphrodites, with exchange of gametes between two individuals, with eggs (in cocoons) buried in damp/moist or aquatic sites. Leeches reproduce by reciprocal fertilization, and sperm transfer occurs during copulation. Similar to the earthworms, leeches also use a clitellum to hold their eggs and secrete the cocoon.


Involves benign skin inflammation upon blood meal, as well enhance secondary infection via viral, bacterial and fungal agents.

Epidemiology and mangement

Leeches are found in fresh water bodies, particularly in slow moving streams, rivers, lakes and pond of the tropics, where residents have intermittent contact with water.



ASSIGNMENT : Leeches Assignment MARKS : 10  DURATION : 1 week, 3 days

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