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Leeches in Australia
Leeches
• Leeches are Annelids (or segmented worms) and are closely related to earthworms.
• There are over 100 different leech species in Australia.
• Leeches have 34 segments, with a powerful sucker at the end.
• Leeches breathe through their body walls.
• Australian leeches vary in size from 7mm up to 200mm when extended.
• They are commonly found in dimly lit places. Most leeches live in freshwater but some live on land, in damp areas of tropical rainforests.
• In Australia’s tropical rainforests the most common leech is the land-dwelling jawed leech (Gnatbobdellida libbata).
• Leeches are hermaphrodites. Each leech has both male and female sex organs. Leeches die after they have reproduced once or twice.
• Leeches are an important part of forest and stream ecosystems because they act as both predators and prey in the life cycle of many animals.
• Leeches are carnivorous. Some prey on invertebrates. They feed on insect larvae, snails, crustaceans and other worms. Their digestive enzymes process their food within a few days.
• Other leeches feed on the blood of vertebrates such as amphibians, birds, reptiles, fish and mammals - including humans! Animals that feed on blood are called sanguivorous. Leeches need symbiotic bacteria to help digest their blood meals which can take weeks or even months.
• Leech bodies are covered with receptors so they can detect warmblooded animals by sight, smell, vibrations and temperature.
• They can also sense carbon dioxide in the air. This indicates there is a breathing animal nearby, which could be their next prey!
• In wet weather the leech waits in foliage or on the forest floor to attach itself to a passing warm-blooded animal. It will wave its head and body around, looking for signals that food is nearby.
• Birds, fish and frogs get their revenge on these bloodsuckers by feasting on them. (Pittas feed leeches to their chicks.) Other predators of leeches are turtles, and the larvae of damselflies and dragonflies.
• Rainforest bushwalkers are a very convenient food source because they brush against low foliage or sit on damp logs or rocks. A waiting leech can easily hitch a ride and grab a snack. When leeches are aware of a meal nearby, they climb the victim’s legs and attach themselves to the first area of bare flesh.
• Leeches use suckers on each end of its body to loop swiftly in pursuit of its host. Once the leech is on the host it looks for a shadowy, protected spot. It holds on tightly with the larger sucker at its mouth, then cuts a hole in the host with its sharp teeth.
• The leech releases an anaesthetic in its saliva which numbs the skin and keeps the host from knowing it is sucking their blood.
• Leeches also release an anti-coagulant called hirudin which stops blood from clotting and keeps it flowing for as long as the leech is feeding. This anti-coagulant also stops the victim’s blood from clotting in the gut of the leech and giving them digestive problems.
• Leeches can consume several times their own weight in just one bloody meal. It can be up to five times heavier than it was at the beginning of its meal.
• When they are full of blood they drop off and find a dark spot to rest and digest their meal.
• After a good feed, a leech can survive several months to a year before feeding again.
• It is difficult to outwit leeches. To keep leeches from biting you, avoid brushing against low vegetation in damp or wet places.
• Cover your socks and shoes with eucalyptus oil or soap. The lather repels leeches. You can also wear pantyhose on the outside of socks and long pants to keep leeches off your legs.
• If you apply insect repellent to your socks and shoes, keep clear of creeks so you don’t pollute the water.
• To detach a leech, carefully expose the leech to heat such as a lighted cigarette or a flame or try sprinking it with salt, tea tree oil, eucalyptus oil, alcohol or insect repellent. Don’t pull leeches off. This can tear the skin which may then become infected.
• If you just want to move the leech on, slide a fingernail under the biting end. (The hirudin might cause the bite to bleed for some time, and the bites are often itchy.)
• Leeches can be dangerous if they fasten themselves to an eyeball. The only safe thing to do is wait for 15-40 minutes until the leech detaches itself and drops off. Don’t pull the leech off and don’t apply salt or you may damage your eye.
• People use leeches in medicine. They are important source of anti-coagulants to prevent blood clots from forming in patients. (Blood clots cause strokes.) Leeches produce vasodilators. Leeches are used in plastic surgery to prevent bruising and in reattaching amputated limbs.
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发表于 25-10-2010 15:47:06
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发表于 25-10-2010 20:55:19
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