Members of the phylum Nematoda contain roundworms which range in size from microscopic to one meter long. Roundworms are unsegmented worms that contain specialized tissues, organ systems and digestive tracts with two openings. Some roundworms live in aquatic habitats, soil, or as parasites which can infect plants and humans. digestive tract begins with an oral cavity or mouth which opens into a muscular pharynx where enzymes are released to begin the breaking down of food. Nematodes do not contain a stomach, so the pharynx leads to the intestines where more enzymes are released and where nutrients are absorbed. The end of the intestine forms a rectum which releases wastes to the anus located at the tip of the tail where wastes are disposed of.
Caenorhabditis elegans (C. elegans) C. elegans, is a non-parasitic free living roundworm measuring one millimeter in length. C. elegans obtains its food from the soil in its environment. C. elegans digests its food in a digestive tract that begins with the pharynx. The pharynx grinds the food and transports it to the intestines. Digestive enzymes in the intestines absorb the nutrients from the food, and wastes leave the body through its anus at the end of the tail.
Necator americanus (New World Hookworm) Hookworms, are parasitic nematodes that reside in its hosts' small intestine, and obtains its food by sucking blood from the intestinal walls of its host. The hookworm digests its food in a digestive tract. Once its food enters the mouth, it enters a muscular pharynx where digestive glands release enzymes to break down the food. The hookworm does not contain a stomach, and the pharynx connects to the intestines where nutrients are absorbed; the digestive tract ends at its anus where its wastes are expelled.
Trichinella spiralis (Trichina worm) Trichinella spiralis are parasitic roundworms that can infect humans, pigs, and rats. It matures in the intestines of its host and obtains its food by sucking blood from its host's intestinal walls. It digests its food by releasing enzymes in the pharynx to break down the food, and then by releasing more digestive enzymes in the intestines to absorb nutrients. Its wastes are then excreted from the anus at the end of its digestive tract.