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Did you know? ... Leeches

Leeches are worms.

Leeches live not only on land and in fresh water, but also in salt water.

Leeches are hermaphrodites, so each leech is both mother and father (but it still takes 2).

Most leeches eat small invertebrates or detritus. Only a few species feed on blood.

All leeches have 34 body segments.

Leeches have a sucker at the front end, surrounding the mouth, and another at the rear end.

Leeches in Australia have 2 jaws and leave a V-shaped wound. In the rest of the world, leeches have 3 jaws and leave a Y-shaped wound.

Australian leeches range in length from 7 mm to about 200 mm when fully extended.

Only Australian and South-East Asian leeches live on land. Land leeches don’t live in water, but can cope with it.

During dry weather, some species can survive for months underground, shrivelled and dry. When water returns, they can be back in action in only 10 minutes.

Blood-sucking leeches can ingest several times their empty body weight. One meal will last for several months.

Leeches have 2 to 10 tiny eyes, which help them locate a meal.

Medicinal leeches used to be popular in 18th and 19th century Europe for their imagined ability to cure all sorts of ailments. During the peak of their popularity, several species came close to extinction on account of enthusiastic collecting in the wild.

Medicinal leeches are used today, but for verified benefits. The most common use is to maintain blood flow in reattached fingers after microsurgery.

Leeches prevent blood clotting by injecting a protein called hirudin. They also inject an anaesthetic that prevents the host from feeling them.

Leeches are not known to transmit diseases among humans, although human viruses have been found in them.

If you are bitten by a leech, you have a few options:

• Let it have its fill, and it will drop off when it is ready.
• Slide your fingernail under each sucker to break the hold and then flick the leech away.
• Apply salt, lemon juice, insect repellent or something else likely to irritate it. This has the possible drawback that the leech can regurgitate its meal along with bacteria into the wound.

Don’t apply a flame, as you can burn yourself.

Leech bites can bleed for many minutes to many hours. The best treatment is to staunch the flow with a firmly applied Band-Aid.

If you are allergic to leech bites and the bite swells and becomes red and itchy, over-the-counter antihistamines can counter the effects. If in doubt, consult your GP.

Further reading

Australian Museum: http://australianmuseum.net.au/Leeches

Wikipedia: http://en.wikipedia.org/wiki/Leeches

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