The leech is a segmented worm With manners impolite.Upon unwilling hosts he feeds His growing appetite. And that is why this annelid Is called a parasite.
LEECHES and earthworms are members of a large group of animals known as annelids, or segmented worms. The leech's body is always divided into segments.
Leeches are temporary parasites which feed upon the blood of higher animals. You know that the animal upon which a parasite feeds is called a host. Frogs, turtles, cattle, and sometimes human beings, may be the hosts of leeches.
Blood is not the only food of leeches.
They will eat tadpoles, snails, worms, and other small animals living in ponds. Different kinds of leeches have somewhat different food habits. Thus, a leech may be a cannibal, a scavenger, a parasite, or a free-living animal, but it is said that he will usually make a meal of blood when he can get it.
Years ago many people believed that letting blood from a patient's body would cure his illness. The large medicinal leech which was often used for this purpose can take two or three times its own weight in blood into its body at one feeding. The leech's saliva mixes with the blood of the host and prevents it from clotting while the leech is feeding. After a meal, its body is short and broad, and it will drop off the host of its own accord. A leech digests blood slowly and can live on a single meal for a long time.
You may see leeches swimming through the open water or moving over submerged plants or logs. A sucker is located at each end of the leech's body. The mouth is in the
oral or anterior sucker. The posterior sucker is at the other end of the leech's body. Like his relative, the common earthworm, a leech does not have legs. His suckers are useful not only to attach his body to some object but assist him in locomotion as well. When he moves he may remind you of a measuring worm.
A leech does not have gills or lungs for respiration. Many fine blood vessels near the surface of his body take in oxygen and give off carbon dioxide.
Large American leeches are about six inches long. Adults of others are from one to four inches in length, but you may find young ones which are quite small. Leech eggs are usually covered with a cocoon which the parent attaches to stones or other objects. A few leeches bury their egg cocoons in moist earth. Others living in streams on the under surface of stones have the odd habit of attaching their eggs to their own bodies. After the eggs have developed into young leeches, you may see
dozens of them clinging to the under side of the parent's body.