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CRITTER SPOTLIGHT: North American Leech: Marcobdella decora


Good Morning Watershed Explorers,


Leeches have long been the focus of horror films and nightmares, mostly due to their characterization as a bloodsucker. However, not all leeches suck blood. The majority of leeches are not parasitic and feed on worms, aquatic insects, and snails. Leeches are important to a variety of ecosystems. They are food for other organisms and can also be used in traditional medicine. Leeches can be found in a variety of habitats including marine, freshwater, and terrestrial (on land). The focus of this post is the North American leech, Marcobdella decora. These leeches are found in freshwater and are a type of parasitic leech.


The North American leech can grow over 2 inches in length. It is usually brownish-green and can have dark spots. Like most leeches, the North American leech has suckers on both ends and is reported to have five pairs of eyes. An interesting fact that will come up in almost any search on leeches is that leeches have 32 brains. This is a little deceiving. Leeches do have 32 segments, and each segment does have nerve endings that act as a brain. Most research shows that these nerve endings still connect to one internal brain that is divided up into 32 different sections.


Unlike other parasites, parasitic leeches do not transmit disease to humans. They also don't take much blood when they bite, and their bites are painless. To avoid leeches, it is best to stay out of slow-moving, swampy, freshwater.


North American leeches are excellent swimmers and can detect prey several yards away. They primarily feed on the blood of amphibians and fish, but on occasion will attack mammals. Leeches only need to feed every few months.


Leeches lay about ten eggs at a time which are placed in cocoons that are positioned on the edge of water bodies. Once the eggs hatch, the young can swim directly into the water.


Leeches are sometimes associated with polluted water because they don't require a lot of dissolved oxygen. However, it is not uncommon to find leeches in healthy water bodies.


I hope you enjoyed learning a little more about the North American leech.


Happy Exploring,

Mrs. Morissette


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