Leeches are annelids comprising the subclass Hirudinea. There are fresh water, terrestrial, and marine leeches. Like the Oligochaeta, they share the presence of a clitellum. Like earthworms, leeches are hermaphrodites.
The European Medical Leech (Hirudo medicinalis) and some congeners as well as some other species have been used for clinical bloodletting for thousands of years. But most leeches do not feed on blood, but hunt small invertebrates, which they devour whole.
Haemophagic leeches attach to their hosts and remain there until they become full, at which point they fall off to digest. Leeches' bodies are composed of 34 segments. They all have an anterior (oral) sucker formed from the first six segments of their body, which is used to connect to a host for feeding, and also release an anesthetic to prevent the host from feeling the leech. They use a combination of mucus and suction (caused by concentric muscles in those six segments) to stay attached and secrete an anti-clotting enzyme into the host's blood stream.
Some species of leech will nurture their young, providing food, transport, and protection, which is unusual behavior in an invertebrate.
Monday, June 9, 2008
Tories have little room to grow, Liberals preferred choice in polarized vote: poll
Wow. There's a shocker. Anyway, I have to concentrate more on the nature of my blog.