Medicinal leech
Scientific name: Hirudo verbana
Country: Albania, Armenia, Austria, Azerbaijan, Belarus, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Georgia, Germany, Greece, Hungary, Ireland, Italy, Kazakhstan, Latvia, Lithuania, Luxembourg, Moldova, Netherlands, Norway, Poland, Portugal, Romania, Russia, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom, Yugoslavia
Continent: Europe, Asia
Diet: Blood of birds, fish, frogs, mammals
Food & feeding: Carnivore
Habitats: Freshwater
Conservation Status: Near threatened
Relatives: Earthworm, lugworm
Description: Leeches have segmented bodies like an earthworm. They have a sucker at the head, surrounding the mouth and at the tail end. The mouth contains three jaws that can break the skin of their hosts to suck their blood. Medicinal leeches are greenish brown on their backs with thin red stripes running along the body and paler below. They grow up to 20 cm in length.
Lifestyle: Leeches live in shallow muddy pools and ponds with plenty of waterweeds. When hungry, they attach themselves to a passing animal, break the skin with their jaws, and inject special chemicals that prevent the blood from clotting and reduces any pain. They then suck the blood of the host until they are full, when they withdraw their jaws and drop off into the water. They can consume 15 grams of blood, ten times their own body weight, before they are full. They only need to feed every six months.
Family & friends:Leeches are true hermaphrodites, having both male and female parts, but they still need to come together to mate with each other.
Keeping in touch: Leeches have a number of ways of sensing the outside environment. They can detect changes in temperature which can help with prey location. They also have 5 pairs of eyes that can determine light intensity.
Growing up: After mating, 15-50 eggs are laid in a spongy case or cocoon, above the waterline often under stones. The eggs hatch in three to five weeks and the young leeches need two seasons of feeding before they are ready to breed themselves.
Conservation news: The removal of millions of leeches for medical use in the 19th century reduced the numbers of wild leeches dramatically and in the last century, numbers were reduced further due to drainage of the ponds and ditches that they live in. The reduction of plough horses on farms (now replaced by tractors) has also affected leech numbers as horses used to be a favourite source of blood when they went to drink in ponds and ditches. Thankfully medicinal leeches in the wild have made a great recovery in much of its UK distribution.
