Chapter 34Section 2

Phylum Nematoda & Rotifera

Phylum Nematoda• Roundworms (pseudocoelomates)

• Bilaterally symmetrical

• 1mm-120mm (4 feet)

• Digestive tract with two openings (mouth & anus)

• Cuticle- protective covering

Phylum Nematoda• Most are parasites and more than

50 species are parasites in humans

• Common roundworm studied by scientists in developmental biology is C. elegans

Ascaris• Genus of roundworm parasites

that live in pigs, horses, and humans

• Feed on food in intestines of host

• Females produce 200,000 eggs per day

Hookworms• Hookworm- intestinal parasite

• Have cutting plates that clamp onto the intestinal wall

• Feed on host’s blood

• Cause anemia• Like Ascaris, hookworms release

eggs

Trichinella• Form cysts in muscle of host

• Found in undercooked meat

• Trichinosis- disease causes muscle pain & stiffness

• Farmers no longer feed meat to hogs and freeze meat

Other Parasitic Roundworms

• Pinworm- most common roundworm parasite in the USA

• School age children

• Does not cause serious damage

• Found in feces

Other Parasitic Roundworms

• Filarial worms- disease-causing roundworms that infect over 250 million people in tropical countries

• Causes elephantiasis- limbs become swollen and skin hardens and thickens

Other Parasitic Roundworms

• Dogs & cats

• T. canis and T. cati

• Live in the heart and large arteries of the lungs

• Heartworm disease

Phylum Rotifera• Rotifers

• Transparent, free-living animals that live in freshwater

• Cilia surrounds the mouth- helps sweep food in- algae, bacteria, & protozoa

Phylum Rotifera• Food moves from mouth to

mastax- muscular organ that breaks down food

• Food is absorbed then passes from intestines to cloaca- common hole which reproduction, digestion, and excretory systems empty

Phylum Rotifera• Rotifer reproduction

• Parthenogenesis- unfertilized eggs develop into adult females

• Other eggs form into males and the males fertilize other eggs with sperm

REVIEW!!!• Identify two characteristics of the

Phylum Nematoda and the Phylum Rotifera.

• What is the name of the most common roundworm studied by scientists in developmental biology?

• What type of worm causes elephantiasis?