The thought of leeches would gross some people out, as it is a type of worm that attaches itself to various animal prey and feed on its blood (I do not suggest a google image search of leeches!). However, some incredible characteristics of leeches attract biologists, mathematicians, and doctors.
DNA from blood in leeches are used to study shy or rare animals that are hard to encounter. Many animals in tropical forests are difficult to find due to their shy or cryptic nature, and this becomes a problem for endangered mammals that need to be closely monitored. Instead of going through the trouble of searching for the mammals or collecting traces of them, scientists turned to leeches. Since leeches feed on blood from other animals, scientists can extract DNA of whatever was prey to the leech within the last 4 months. With this information, scientists were able to better confirm the existence or distribution of threatened species, study genetic characteristics, and even discover new species.
Leeches have a weird pattern of heart beats! The human heart pumps blood around the body as its 4 chambers – 2 on the right, 2 on the left – contract in turns. In contrast, the leech heart has a row of 10-15 chambers on each side (right and left) of its body. As Ian Stewart describes eloquently in his book Mathematics of Life, all the right side chambers first beat in sync. At the same time, the left side chambers take turns, sending a wave of pulses from the back to the front of the leech. After 20-40 beats, the left and right side patterns switch, so now the left chambers beat together, while the right chambers beat in sequence. At any moment, one side of the heart is beating together, while the other side beats in a wave. Extensive studies model the neurological driving forces of this odd heart beat, but scientists still don’t know why they beat this way.
The chemicals that leeches secrete are helpful in surgery. When a leech attaches itself to its prey, it secretes a natural anaesthetic and anticoagulant that keep blood from clotting and allow it to keep flowing until the leech is full. To surgeons, this makes leeches useful tools to allow a healthy blood flow while amputated parts of the body are reattached. Records from as early as 2500 years ago suggest that leeches were used for medicinal purposes to draw blood out of a patient to cure various illnesses. Though these older methods are no longer supported by scientific evidence, the legacy of the “medicinal leech”, Hirudo medicinalis, carries on to modern medicine.