General Information: The Annelida are a large phylum of segmented worms with over 17,000 modern species including ragworms, earthworms and leeches. They are typically found in moist environments. This phylum is divided into five subphylums that include:
1. Polychaeta
2. Clitellata
3. Myzostomida
4. Archiannelida
5. Echiura
1. Polychaeta
2. Clitellata
3. Myzostomida
4. Archiannelida
5. Echiura
Lumbricus terrestris (nightcrawler)
The gut of the earthworm is a straight tube, which extends from the worm's mouth to its anus. Food enters through the mouth. Food moves into the esophagus, where calcium is pumped in to maintain proper blood calcium levels in the blood and food pH. From there the food passes into the crop and gizzard. Once through the gizzard, food continues through the intestine for digestion. The intestine secretes pepsin to digest proteins, amylase to digest polysaccharides, cellulase to digest cellulose, and lipase to digest fats. After this it goes to the excretory system.
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Hirudo medicinalis (Medical leech)
In feeding they slice their way through the skin of the host, leaving a Y-shaped incision. Behind the blades is the mouth, located ventrally at the anterior end of the body. It leads successively into the pharynx, then the esophagus, the crop, the gizzard, and the intestinum, which ends at the posterior sucker. Once food travels to the gut, amino acids are unwinded one monomer at a time. This digestive system of this leech takes such a long time that it only needs to feed twice a year.
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Alitta virens (King Ragworm)
Ragworms get their food into their system by using a net-like mouth or using their jaws to eat at their food. They have a direct path from the mouth to the anus, without a stoppage in a heart or anything of that sort. The food goes through the mouth and into the esophagus where it immediately goes into the intestine. Nutrients and the like are passed around to the needed areas of the worm, and then the waste is passed on to the anus.
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