Clam Worm
It is a freeswimming polychaete, scavenging on the bottom of shallow marine waters. It feeds on other worms and algae. To feed, it uses a proboscis, which has two hooks at the end, to grasp prey and draw it into its mouth. Clam worms feed on algae and other invertebrates that they find by burrowing in the sand or mud. The oral cavity is lined with cuticle, which is often strengthened with ridges or other structures, and, especially in carnivorous species, may bear a number of teeth. The mouth often includes a sharp stylet, which the animal can thrust into its prey. In some species, the stylet is hollow, and can be used to suck liquids from plants or animals.
Tube Worm
The worms' white tube home is made of a tough, natural material called chitin. Tube worms do not have a mouth, eyes, or a stomach. Their survival depends on a symbiotic relationship with the billions of bacteria that live inside of them. These bacteria convert the chemicals that shoot out of the hydrothermal vents into food for the worm. This chemical based food-making process is referred to as chemosynthesis. Scientists found that during its earlier stage, the tubeworm does have a mouth and stomach for bacteria to enter. But as the worm grows, these features disappear
Strongylus Vulgaris
It has a large mouth opening that leads to a buccal cavity with thick walls that often contain teeth. The buccal cavity leads directly to an esophagus that is muscular and used to pass food into the intestines via pumping action. The intestine is a straight tube generally circular consisting of hundreds of projecting microvilli used in absorption and because of their vast numbers provide an immense absorptive capacity. The intestine terminates in a rectum in females and a cloaca in males. In either case, the cloaca and rectum lead to an anus which usually opens to the outside at the end of the body.