It serves as a circulatory system and also makes the worm rigid, like a hydrostatic skeleton. Roundworms are parasitic to both animals and plants. Some examples are trichinella, found in pork, pinworms, hookworms, and brainworms. In lab, we collected deer feces, enticed the brainworm larvae out of the feces with warm water, and collected the sample to study under the microscope. The larvae of the brainworm is found in the deer feces.
Snails eat the larvae.
Later, deer eat the snails and come in contact with the brainworm as larvae again. This larvae penetrate into the gut of the deer and get into the nerves. They migrate up into the spinal cord where the adults are formed. The adults live in the sinuses and surrounding tissues of the brain, but cause few problems for the deer. The eggs are taken by the blood vessels to the lungs where they hatch into larvae.