During winter, they survive by burrowing into mud below the frostline. Although hermaphroditic, they reproduce sexually, with both leeches exchanging sperm. They deposit eggs in a cocoon, which they then typically attach to a rock or log underwater until the baby leeches emerge. The timing here depends on the species of leech. One of the bloodsucking leech species common in our region is Macrobdella decora , also known as the North American medicinal leech, although the European species Hirudo medicinalis and Hirudo verbana have been used more commonly for medicinal purposes.
While the medicinal use of leeches, which stretches back thousands of years, was often dubious, a modern version of the practice has been making a comeback in recent years.
While pharmaceutical anticoagulants tend to be strong and can cause bleed-outs in remote parts of the body, leeches, Weaver said, target the specific area that needs treatment. All of this may seem irrelevant for the swimmer who jumps into the water for refreshment and comes up with a leech — or several — attached. If leeches make you squirm, just be glad to live here, where leeches typically measure only an inch or two and are confined to shallow water.
So leeches, like all blood suckers, usually like to bite without causing too much pain. They like to bite in spots where they are hard to find.
The other thing leeches have to worry about is that blood clots. A blood clot forms whenever you get a cut which stops bleeding in a few minutes — eventually the blood clot forms a scab. This happens when blood contacts the air. It clumps together and forms a solid lump. The leech cannot feed if the blood forms a lump and so it releases a chemical that prevents this clumping.
This keeps the blood flowing so the leech can suck for two or three hours without stopping. That way it collects enough food to last until it finds another animal to bite. Read more: Curious Kids: how does our heart beat? Leeches are not the only animal that feeds on the blood of animals. Others include mosquitoes, ticks, vampire bats yes they exist, but only in South America , bed bugs, lice, other insects and the lamprey fish.
Parasites all live on or in other animals and many of them feed on blood. The average human adult has about 4. After a feeding, leeches can subsist on the blood for several months. So we decided to only count one feeding per leech since your body will reproduce all the blood long before they need to feed again. Of course, a human would die long before bleeding out completely. We used Hirudo Medicinalis , a common medicinal leech for these numbers.
Swarms can be anywhere from 10s to s. And leeches have been observed in large group formations. In theory, an opportunistic leech swarm could attack and kill a fully grown adult. Although that would rely on the human not fighting them off. There have been deaths from people in North Kenya drinking water containing the Myxobdella Africana leech. The victims suffered anemia, resulting in death.
In cases treated with blood transfusions, the patients have survived. Not to forget, as recently as , a 65 year old man in Turkey was rushed to ER with leech bites.
Fortunately, he survived after receiving 8 units of frozen plasma. Still, most of the time, leeches are low to no risk. Their bad reputation comes from their blood-sucking nature and their virtually alien genetics. A blue whale is big. And not the way other animals are. But in a blue whale, their blood alone weighs 14, lbs. An entire blue whale is more like , kg about twice the weight of a space shuttle.
So depending on the size of the leeches it would take about thousand to 2. Or about thousand to 1.
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