Annelids
Annelids are a phylum of worms whose bodies are separated into segments. Annelids are divided into two major groups. The first is Polychaetes and the second is Clitellates. They have over 17,000 species today, some species can be found on land, but most are found in marine environments. Although there is no single characteristic that distinguishes Annelids from other Invertebrate phyla, they have a specific combination of characteristics. For example, their body is segmented on the outside by ring like constrictions called annuli and on the inside by septas at the same point. Their bodies are long and covered by an outer coating that does not contain cells, but actually is made and secreted by the cells underneath. This outer covering is called a cuticle and is made of tough and flexible collagen. Also most Annelids have a closed circulatory system where their blood is moved throughout its entire body via blood vessels. They have a one way digestive that runs from the mouth to the anus. This allows Annelids to continually digest food and release it as waste.
Leeches
Leeches are a segmented worms that belong to the Annelid Phylum. They use a form of mucus to stick to their prey. While they are attatched, they use "suckers" in order to feed off the blood of their prey. Their digestive system begins with the jaw witch is extends to their esophagus. The esophagus extends down to the leeches crop. The crop is a leeches form of a stomach. The crop acts as a storage compartment which allows the leech to hold up to five times its body size. Because of an anticoagulant the leech produces, all the blood stays in a liquid form. The crop then extends to the gizzard. The gizzard has bacteria and enzymes in it which help the leech break down and digest the blood. The digested product is then absorbed in the leech's intestinal wall.
Earth Worms
Earth Worms are a species that also belong to the Annelid Phylum. It's digestive system begins with the worms mouth. Because it has no jaw or teeth, the worm uses its muscular pharynx to suck in soil containing food. The soil and food then go through its esophagus into the worms crop. The crop stores the food temporarily. It is then forced into a very muscular organ called the gizzard. The gizzard contract and expands causing whatever is inside to run together. By doing this the worm's food is ground up. The food is digested in te intestine which stretches almost the entire length of the worm. In the intestine enzymes break down the food. Then the digested food is absorbed by the blood which circulating through the intestine walls.
Nereididae (RagWorms)
Nereididae or otherwise known as RagWorms are a species belonging to the Annelid Phylum. Ragworm's teeth are made of a very tough, yet lightweight material. Unlike bone and tooth enamel, this is not mineralized with calcium. It is formed by a histidine rich protein, with zinc bound ions. Ragworms are mainly omnivorous but many are active carnivores.