Facts about Leeches
Animals with unusual properties
Leeches, being eurytopic animals, are common on almost every continent. Although they usually lead a parasitic or predatory life, they have been used by humans for centuries for medicinal purposes. In the past, they were used for bloodletting, today, kept in sterile cultures, they support various medical therapies.
1Leeches (Hirudinea) belong to the phylum Annelida.
Annelida includes more than 500 species, which are equipped with one or two suckers. Most of them are erybionts, organisms that show excellent tolerance to environmental factors. They can live in a wide variety of conditions and colonize large areas of the earth. In addition to leeches, eurytopic species include the house sparrow, the common reed, and the common bracken.
2Leeches have a parasitic or predatory lifestyle.
Most are aquatic or amphibiotic (adapted to live both in water and on land); species that live on land are rare.
3Leeches are found in inland freshwaters as well as in marine waters on all continents except Antarctica.
They can live in freshwater, brackish water, saltwater, and on land. Leeches prefer shallow, still, or slow-moving water. They are not found in rushing mountain streams or raised bogs. Those adapted to life on land (few) inhabit the litter of tropical forests, such as the Ceylon leech.
4The body of leeches is elongated, obovate, or dorsoventrally flattened and may range in length from a few millimeters to over 30 cm.
Their bodies are contractile and distinctly segmented, tapering towards the ends ending in one or two suckers. The suction cups are used by the leeches to attach to the substrate, and by the bloodsucking species only to penetrate under the skin of their prey - for sucking they use their strongly muscled pharynx and esophagus. The anterior sucker contains the mouth opening.
5The cephalic segment of the leech is made up of a prostomium and four segments.
Eyes are located on the prostomium. There may be from one to ten pairs of different shapes and sizes. Eye positioning varies between species, and there are even ones that do not have eyes at all.
6The body color of leeches is shades of brown and green with a hint of black.
7In water, leeches move in a wavy, meandering motion.
They move in a similar way to the caterpillars, with the help of suction cups - they extend their bodies forward, attach themselves to the bottom with the front suction cup, and move by contracting the rest of their body.
8The vast majority of leech species are parasites, the rest being predatory species.
Parasitic species, which are permanent external (rarely internal) parasites, feed on the blood of vertebrates or the body fluids of invertebrates. Predatory species prey on invertebrates, fry, and tadpoles.
9Leeches are hermaphrodites.
They use cross-fertilization and developed complex mechanisms to prevent self-fertilization. Leeches lay their eggs in a cocoon (the number of eggs ranges from 1 to 300) attached to plants, stones, in the soil, or on the underside of the parent organism. Simple development (no metamorphosis) takes place in the cocoon.
10The young hatch fully formed and adapted to independent life.
Many leech species take care of their offspring by carrying the young on the abdominal side of the body for some time.