Leech

The leech (Hirudinea) is a predator and blood-sucking parasite that is native to almost every continent. This aquatic worm is a member of the Annelida phylum, which means it’s related to the earthworm.

Leeches have a bad reputation among humans. We consider them bloodsucking pests and use the term “leech” as an insult. Most of them don’t attack humans, however, and many don’t depend on blood as their main diet. In ancient times, they were used medicinally. Today, doctors use medical leeches to clean delicate tissue during surgery.

Have you ever been out hiking in a damp area, or gone fishing in some wetlands, and later that day discovered a leech attached to your lower leg? It would leave more than a couple of folks screaming for help, while others may just shrug it off–then pull it off. So how would you wind up with a leech attached to one of your extremities in the first place? Where do leeches live? Read on to learn more about these intriguing invertebrates, including the answer to that burning question.

5 Amazing Leeches Facts!

• They have 10 eyes, but they have poor eyesight.
• They can go 6 months without feeding.
• Leeches live in every continent except Antarctica.
• Some people use them as fishing bait.
• Leech therapy is an accepted medical practice.

Scientific Name

The leech’s scientific name is Hirudinea. There are over 680 different species or types of leeches. Of these, 100 are saltwater leeches, 480 are freshwater and the rest live on land. Land-dwelling leeches usually live on the banks of ponds and lakes. They are invertebrates that are members of the Annelida phylum, which is the phylum that includes earthworms.

The scientific name comes from the word hirudin. Hirudin is a naturally occurring peptide in the salivary glands of bloodsucking leeches that prevents blood clotting.

Types of Leeches

• Kinabalu Giant Red Leech – The Kinabalu Giant Red Leech definitely lives up to its name. This insect is bright reddish-orange in color and is twenty or more inches long. It’s found on a mountain in Borneo. Kinabalu giant red leeches are carnivores eating a worm that lives alongside it in Borneo.
• Piscicola geometra – These leeches can be found in freshwaters of North America and northwestern areas of Europe, in both stagnate and fast-moving water. They do prefer highly-oxygenated waters.
• Hirudo medicinalis – These types of leeches are known as “medical leeches” and can consume ten times their body weight in blood. They have a thin red stripe on is back side.
• Americobdella Valdiviana – The Americobdella valdiviana can be found in South America, particularly in Chile. Its presence of eyes is up for debate, and this leech has yellow front area and grey back side.

Appearance

A leech looks like a fat, dark, and glossy earthworm. It has a solid, segmented body with tapered endings that include a pair of suckers at each end. The leech uses its suction cups to attach itself to the skin of an animal and suck its blood.

A leech typically has two or three rows of tiny teeth. The small size of these teeth is part of the reason you can’t feel a leech bite.

The leech’s body is usually a dark, greenish-brown color with no spots or stripes. Some are so dark that they look black. Leeches vary in size, but a typical one is 2 inches long. The largest leech species is the giant Amazon leech (Haementeria ghilianii), which can grow 18 inches long and 4 inches wide.

Behavior

Leeches usually inhabit in lakes and ponds, and move slowly through the water in search of food. They don’t form complex societies, but they can usually be found in groups together.

Some types of leeches are parasites and predators. They prey on insects and small aquatic animals, and they also suck blood from fish and warm-blooded animals. Their saliva includes an anticoagulant, which keeps the blood of their prey flowing when they bite, and an anesthetic, which prevents their prey from feeling the bite.

They are an important part of pond ecosystems, and some people who keep natural ponds in their gardens put leeches in them for this reason. They are an important food source, and they clean up the waste from dead animals. Pond and fish keepers, however, must be careful to use the right type of leech. Some leeches cause damage to fish by sucking their blood, and this can cause the fish to get sick or weak.

Leeches don’t seek out people, but they will try to grab a meal if you swim or wade in their territory.

Habitat

Most types of leeches live in freshwater ponds and lakes. Their preferred habitat is a warm, slow-moving body of water. They don’t do well in swiftly moving streams or rivers. There are some saltwater leech species, but they mostly live in the ocean depths far from human habitation.

Although leeches prefer warm temperatures, they are extremely adaptable to their environment. They can go a long time without eating, and they will adjust their body temperature to their current environment. That’s why they are found everywhere except the freezing regions of Antarctica.

Diet

Despite their bloodsucking reputation, leeches have a varied diet. While they do suck blood, freshwater leeches also eat mollusks, insects, insect larvae, fish eggs, and worms. When they suck blood, they prefer to suck the blood of other water creatures, including worms, snails, and fish.

Some types of leeches are scavengers who feed on dead animals and plants. Only a small percentage sucks the blood of mammals.

History and Evolution

While there are other parasitic animals in the world, the leech has evolved to be especially successful at feeding well and feeding undetected. The saliva of the leech is comprised of roughly thirty different elements, which tells us that it has been one of its most impressive adaptations. Leeches evolved over time to have saliva that numbs their hosts and also keeps the blood flowing freely.

Predators and Threats

Leeches are an important food source for fish, turtles, and ducks. Their population is stable and isn’t vulnerable to any threats. Any activities that harm pond life will harm all types of leeches.

Reproduction and Life Cycle

Leeches are hermaphrodites, and there are no differences between males and females. During reproduction, they use cross-fertilization. Once the leech’s eggs are fertilized, the female lays them in a cocoon. There may be anywhere from 1 to 300 eggs in the cocoon. The female then attaches the cocoon to a fixed place like a plant or stone.

Baby leeches develop inside the cocoon. Unlike moths and butterflies, which go through several stages in the cocoon, they develop to their full size. In some cases, the mother leech carries the cocoon on her body to protect it.

Development of the young inside the cocoon can take up to nine months. Leeches are born fully formed and ready to live on their own. They reach sexual maturity in two years.

Where do leeches live with regard to others of their kind? Leeches are solitary and only mingle with other leeches during reproduction.

Compared to many invertebrates, they have a long lifespan. They can live up to 10 years in the wild. Their lifespan in captivity is even longer.

Population

There are no estimates of leech populations in the world. They live in every part of the world except Antarctica, and their population is not threatened.

Likable Leeches?

We hope you’ve learned some interesting facts about these common, creepy but harmless animals. Like all animals, they play an important role in their ecosystems. They may not be lovable, but they’re not dangerous.

1. The Knowledge Burro: What Does Hirudinea Mean? FactInformer: 20 Facts About Leeches. Healthline: What Is Leech Therapy?, Available here: https://theknowledgeburrow.com/what-does-hirudinea-mean-in-latin/
2. FactInformer, Available here: https://factinformer.com/facts/82/about-leeches/#:~:
3. Healthline, Available here: https://www.healthline.com/health/what-is-leech-therapy