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| Leeches
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Arhynchobdellida Rhynchobdellida
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The leeches are clitellate when breeding and are derived from some oligochaete ancestor. They attach to their hosts and remain there. Leeches' bodies are composed of 32 segments. They all have a ventral sucker formed from the last six segments of the body, and that is a combination of mucus and suction caused by concentric muscles formed from the circular muscles of the segments from which the sucker is derived. Like earthworms, leeches are hermaphrodites.
Some species of leech will nurture their young, providing food, transport, and protection, which is unusual behavior in an invertebrate.[1]
All leeches are from one of three orders:
The leech has long been used in medicine, although today its use is mainly limited to limb reattachment procedures instead of the wide-ranging medical use of the past. Leeches were once so commonly used that doctors were popularly called leeches. In Old High German, lāhhi ( etymon of leech) means "physician".
Leech saliva contains a number of compounds which assist in its feeding. An anaesthetic limits the sensations felt by the host (and thus reduces the chance of the host trying to detach the leech). A vasodilator causes the blood vessels near the leech to become dilated, and thus provide the leech with a better supply.
Lastly, the leech saliva contains a complex protein called hirudin , which is a highly effective anticoagulant. The leech needs this to prevent blood clots (which would block its feeding) from forming in the wound created by its mouthparts. These properties are difficult to achieve using other medical techniques, and it is for this reason that leeches have come back into clinical practise in the last 25 years. The small amounts of hirundin present in leeches makes it unsuitable to be harvested for more general medical use, so hirudin (or related chemicals) have been synthesised using recombinant-DNA technology.
Bdellatomy is the practice of cutting the leech open slightly while it is sucking blood to let the blood in it out, so thinking that it is not full yet, the leech continues to bite instead of detach itself. This practise was first recorded in 1868 by Daily News .
The anatomy of medicinal leeches may look simple, but more details are found beyond the macro level. Externally, medicinal leeches tend to have a brown and red stripped design on an olive colored background. These organisms have two suckers, one at each end, called the anterior and posterior sucker. The posterior is mainly used for leverage while the anterior sucker, consisting of the jaw and teeth, is where the feeding take place. Medicinal leeches have three jaws that look like little saws, and on them are about 100 horny teeth used to incise the host.
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