Monday, March 5, 2007

General Characteristics

Annelids are triploblastic protosomes that have a complete coelom. They have a closed circulatory system (blood is contained inside blood vessels) and are segmented. The segmentations are called Septa.

Oligochaetes and Polychaetes typically have spacious coeloms, but in leeches, the coelom is filled in with tissue and reduced to a system of narrow canals.

Typically, each compartment corresponds to a single segment of the body, which also includes a portion of the nervous and circulatory systems, allowing it to function somewhat independently. This means that if part of it is cut off, it can still function without the other half since it has the nessecary parts in each segment!

Each segment is marked externally by something called an Annuli. Annelids have a wide variety of diets, including active and passive hunters, scavengers, filter feeders, deposit feeders, and blood-suckers. Annelids have two main blood vessel; dorsal and ventral blood vessel.

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