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The Nematoda Members of this phylum are referred to as roundworms.

They have long, thin bodies that are tapered at both ends. Roundworms are pseudocoelomates.

They have a “false” .

It is a hollow, fluid filled , but is only partially lined with tissue. Roundworms have a “tube within a tube” digestive system:

The digestive system has two openings: a mouth and an .

Food enters the mouth and wastes leave the body through the anus. Examples of Roundworms Include:

Ascaris

Trichinella Pinworms

Where is this commonly found?

Ascaris in the intestines of pigs, horses, , , etc. What happens if Ascaris becomes too numerous in the ?

They can completely A female can block the produce 200,000 intestine of per day. the host. Hookworms

The ’s mouth has cutting hooks that clamp to the intestinal wall of the host. Hookworm’s feed on the of the host.

The live in the . They enter a host by boring through the bottom of the feet. Trichinella are the smallest parasite of humans, have an unusual lifecycle, and are one of the most widespread and clinically important parasites in the world. The small adult mature in the intestines of a definitive host such as a pig. Each adult female produces batches of live larva, which bore through the intestinal wall, enter the blood (to feed on it) and lymphatic system, and are carried to striated. Once in the muscle, they encyst, or become enclosed in a capsule. Humans can be infected by eating infected , horsemeat, or wild such as fox, , or bear. Trichinella The best way to prevent trichinellosis Don’t eat is to cook meat to safe undercooked meat, temperatures. A food especially PORK! thermometer should be used to measure the internal temperature of cooked meat. Do not sample meat until it is cooked. Prevent Contamination

•Wash your hands with warm water and soap after handling raw meat. •Curing (salting), drying, smoking, or microwaving meat alone does not consistently kill infective worms; homemade jerky and sausage were the cause of many cases of trichinellosis reported to CDC in recent . •Freeze pork less than 6 inches thick for 20 days at 5°F (- 15°C) to kill any worms. •Freezing wild game meats, unlike freezing pork products, may not effectively kill all worms because some worm species that infect wild game are freeze-resistant. •Clean meat grinders thoroughly after each use. To help prevent Trichinella in populations, do not allow pigs or wild animals to eat uncooked meat, scraps, or carcasses of any animals, including rats, which may be infected withTrichinella. Pinworms

Pinworms infect 16% of adults and 30% of the children living in the United States.

Since the eggs are laid on the outside of the body, the eggs may be stick to a person’s hands. Anything the person touches will become infected with these eggs. Ways to control parasitic worms:

Good meat inspection.

Cook all meats thoroughly.

Wear shoes in areas occupied by host animals, such as barns, pastures, etc.

Wear protective clothing when wading in waters that may be infested with parasites. Evidence of Parasitic Worms in Humans Compare and contrast the body plans of with roundworms.

Similarities: Both have three germ layers and bilateral . They both have anterior and posterior ends allowing to occur. Differences: 1.The roundworm has a body cavity called a coelom. It is a false coelom (pseudocoelom) because it is not completely lined with mesoderm tissue. A has no body cavity and is called an “acoelomate”.

2.A roundworm has fluids that circulate through the body; a flatworm does not.

3.A round worm has a tube within a tube digestive system, with a mouth at one end and an anus at the other end. A flatworm has a digestive system with only one opening. What is cephalization? What is the advantage of cephalization?

Cephalization means that the and organs are concentrated in the anterior part of the body. This allows the organism to meet its environment on, allowing quicker responses to the environment. How can parasitic worms survive when they no longer have a digestive system? What is this concept called?

They have no need for a digestive system. They absorb food that has already been digested by the host. The loss of a body system is called “degeneration”. How is the body shape of a parasitic roundworm an adaptation for its way of ?

The roundworm body is long and slender and tapered at both ends. This allows the roundworm to move easily through the tissues of the host. How can a flatworm survive without a circulatory or a ?

A flatworm is so flat that none of its cells are ever very far away from the external environment. and move by between the body cells and the environment.