Even though leeches are similar to earthworms, leeches have suckers on both ends and the earthworm only has one. However, some primitive leeches will have a single sucker at the back. Each leech is structured with 34 segments. The first five contain the brain, eyes, and one sucker; the middle 21 have nerves and reproductive organs; and the last seven have a posterior brain and tail sucker.

Leeches have 32 brains! With their nervous system being so similar to ours, they are often used in the study of invertebrate nervous systems, and brain and cardiovascular disorders. Their complex nervous system can detect touch and vibrations from nearby objects. For example, leeches that feed on warm-bodied prey can sense heat and will move towards warmer objects.

In fact, leeches are found on every continent in the world except for Antarctica, and even then, they can still be found in the Antarctic waters! Leeches can usually be found in marshes, rivers, and ponds, with 1/5 of leach species being found in the sea.

Leeches that consume blood use their suckers to attach to mammals, reptiles, birds, and fish. Their teeth are so sharp, they’re even able to pierce the thick skin of hippos. Leeches can ingest amounts of blood five times bigger than their own weight allowing them to go up to a year between meals!

Leeches are known as protandric hermaphrodites, which means they change sexes throughout their life span. They will first have male reproductive organs and then later develop female parts. Some leeches can self-reproduce, not needing a partner, while other species require a male and female. Depending on the species, the female will either lay eggs or produce a cocoon!

Scientists have discovered over 700 different species of leeches.

Leech bites are usually more alarming than hazardous; however, some people are highly allergic to leech bites and will need urgent medical attention.