What is Phylum Nematoda - Roundworms?
Nematodes are commonly known as the roundworms. They have a pseudocoelom type of body cavity, and they have a digestive tract that opens through a mouth and anus. Their bodies are relatively simple. Gases and wastes are exchanged with the environment directly through their body walls. Their nervous system consists of clusters of nerves called ganglia in the anterior head region of the body, and nerves run longitudinally down the body. Muscles enable the worm to move the body in a whiplash fashion, propelling it through the water. Reproduction in roundworms is sexual, and large numbers of eggs are usually produced.
Nematodes live just about everywhere on Earth-in the soil, as internal and external parasites on and in animals and plants, in fresh water, and in salt water. Because of this fact, some have imagined that if you could actually dissolve all of the soil and water, plants and animals on earth-except for the Nematodes-the Nematodes remaining would outline where the soil, water, plants and animals once were!
Several Nematodes are important parasites of humans and domestic animals for health reasons. These Nematodes live in the intestinal tracts of chickens, dogs, cats, pigs, and cattle. Eggs are shed with the feces and can be ingested by a new host. You have probably heard at one time or another about someone "having a dog (or cat) wormed" at the veterinarian's office. These roundworms are the worms to which the phrase refers. Some other common parasitic roundworms are pinworms; hookworms; heartworms; Trichinella, which causes the disease trichinosis; and filarial worms, which cause elephantiasis, a horrible disease that clogs the lymphatic vessels.