Freshwater Leech

Phylum Hirudinea
Monday, June 21, 2010
Leeches are a fairly common resident of the Mountain Lake pond. They are annelids (segmented worms), and can be found in most fresh water ponds and lakes. They are hermaphrodites, like most annelids. All leeches’ bodies are composed of 34 segments. The first six segments make up the oral sucker, which is used to attach to a host for feeding. They have another sucker at the anterior end used to move “like an inchworm.” All leeches breathe through their body walls and have eyespots on their head to detect light.
 
Although some leeches consume small insects and larvae whole, this species is mainly a hematophage, meaning that it feeds on blood. The hematophagic leeches feed on invertebrates, fish, frogs, and, notably in the Mountain Lake pond, snapping turtles. Snapping turtles have been found here with more than eight leeches attached to them. They also feed on warm-blooded creatures when the opportunity arises. Although leeches, (especially large ones) can be a significant health detriment to smaller animals, they are not harmful to most large animals. A leech can ingest several times its weight in blood from one host before dropping off and not feeding again for weeks, or even months. Leeches inject hirudin, an anesthetic, to keep the hosts from feeling them break the skin. They also inject an anticoagulant to keep the blood from clotting so that they can feed.
 
Some of the most common predators of leeches include turtles, fish, ducks, and other birds. They are an important part of the pond ecosystem.
 
Leeches reproduce in the spring. They are hermaphrodites, and reproduce through reciprocal fertilization, in which both leeches become impregnated at the same time. The mother leech forms a tough, gelatinous cocoon around the egg mass and attaches it to a hard object or buries it in the mud. The cocoon contains all the nutrient that the young leeches need to survive, and the young emerge several weeks later. Some species nurture their young, which is unusual among annelids. However, most leeches only reproduce once or twice in their lifetimes. Leeches are not capable of regeneration and can only reproduce sexually.
 
Although leeches are mainly nocturnal, they are attracted to disturbances in the water which might indicate food sources. They live mostly in shallow water with many cover objects or hiding places.
 
This leech was intentionally attracted in the station pond with the purpose of capturing it. Jesse Galloway wishes to be listed as a willing blood donor in the name of science. 
Article by Hazel Galloway