A leech can ingest several times its weight in blood from one host before dropping off and not feeding again for weeks, or even months. Leeches inject hirudin, an anesthetic, to keep the hosts from feeling them break the skin. They also inject an anticoagulant to keep the blood from clotting so that they can feed. Some of the most common predators of leeches include turtles, fish, ducks, and other birds.
They are an important part of the pond ecosystem. Leeches reproduce in the spring. They are hermaphrodites, and reproduce through reciprocal fertilization, in which both leeches become impregnated at the same time. Leeches are famous as blood-suckers. The species that feed on blood have special chemicals in their saliva that prevents blood-clotting. Many blood-feeding leeches attack only fish , a few attack any vertebrate including people , and a few are specialists on another group of animals, like turtles or waterbirds.
There are also lots of leech species that don't suck blood. They are predators, eating worms , snails , aquatic insects , and other invertebrates.
Most leeches hide while resting, staying in thick plant growth or hiding in mud. Many leech species are nocturnal, this helps them avoid predators and locate resting prey. If attacked, some species swim away as fast as they can, others go limp and "play dead," others curl into a ball and sink to the bottom. When parasitic leeches attach to their host, they sometimes select places that are hard for their host to reach. Leeches are sometimes important members of aquatic food webs.
They are mid-level consumers, eating smaller animals and in turn being eaten by larger predators. Many leech species are parasites feeding on blood. Some will bite humans. Others may attack domesticated animals that are valuable to humans, such as ducks or fish.
Leeches are used in some medical procedures to remove excess blood from body parts that have been reattached after injury. Carl notices. The tanks are where leeches are born, by the happy meeting of any two of them: leeches are hermaphrodites and very flexible. Carl lifts a corner of muslin covering a tank and picks up one. It is surprisingly beautiful, its belly striped with iridescent gold and green. I select them for colour.
The menu at Biopharm is always black pudding. The leeches ate it more readily, and one cow held the blood volume of 10 sheep. But BSE has ruled out cow blood, for leeches and humans. Carl points out an immobile leech on the bottom of the tank. The bulk of it is storage. A small leech can expand eightfold. Carl sticks his finger in the water and a leech immediately appears. They can digest at different rates. The best method for peace among leeches is to adjust the temperature so they are half asleep and half awake.
The safest leech is a spaced-out leech. Biopharm also experiments with tank size to give leeches the optimal amount of exercise. Carl is tank builder, leech grower, and personal trainer: leeches have to be exercised twice a day. Sometimes it gets more exercise than Carl bargained for.
He has often arrived home to find some attached to his ankles. They stick to your shoe and then they dry out. There may also be a delayed irritation and itching after a bite.
There appears to be no support for the theory that mouthparts left behind after forced removal of the leech causes this reaction. There is no evidence to suggest that they do. The presence of trypanosomes in the gut of jawless leeches has been noted, but jawed leeches do not appear to be hosts. Trypanosomes cause the African sleeping sickness in humans. Leeches transmit trypanosomes that infect fish, crocodiles and even platypus, but none of them are dangerous to humans.
Allergy to leech bite has been reported. Medical opinion should be sought, depending on the severity of the reaction. Trypanosomes of Australian mammals: A review Craig K. Thompson , Stephanie S. Godfrey, R. Andrew Thompson. The Australian Museum respects and acknowledges the Gadigal people as the First Peoples and Traditional Custodians of the land and waterways on which the Museum stands. Image credit: gadigal yilimung shield made by Uncle Charles Chicka Madden.
This website uses cookies to ensure you get the best experience on our website. Learn more. Skip to main content Skip to acknowledgement of country Skip to footer This photo was taken at Somersby Falls, New South Wales, where the leeches were 'searching for blood'. This one was on a leaf and I'm sure it could smell blood as he arched and was looking for a spot to attach.
Introduction Leeches are annelids or segmented worms, and although closely related to the earthworms, are anatomically and behaviourally more specialised. Identification Leeches are segmented worms in the Subclass Hirudinea that are usually ectoparasitic. Habitat Most leeches are freshwater animals, but many terrestrial and marine species occur. Distribution There are around species of leeches world wide. These are divided into two major infraclasses Euhirudinea: the 'true' leeches — marine, freshwater and terrestrial — which have suckers at both ends and lack chaetae bristles Acanthobdellida: a small northern hemisphere infraclass ectoparasitic on salmoniid fish, which lack an anterior sucker and retain chaetae.
The Euhirudinea is further divided into two orders: Rhynchobdellida: jawless marine and freshwater leeches with a protrusible proboscis and true vascular system Arynchobdellida: jawed and jawless freshwater and terrestrial leeches with a non-protrusible muscular pharynx and a haemo-coelomic system. Feeding and diet Most leeches are sanguivorous, that is they feed as blood sucking parasites on preferred hosts.
Leeches are grouped according to the different ways they feed: One group the jawed leeches or Gnatbobdellida have jaws armed with teeth with which they bite the host. The blood is prevented from clotting by production of a non-enzymatic secretion called hirudin.
The land leech commonly encountered by bushwalkers is included in this group. A second group the jawless leeches or Rhyncobdellida insert a needle-like protrusion called a proboscis into the body of the host and secrete an enzyme, hemetin which dissolves clots once they have formed.
Leeches which live on body fluids of worms and small freshwater snails possess such an apparatus. A third group , the worm leeches or Pharyngobdellida have no jaws or teeth and swallow the prey whole.
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