Among the most numerous of animals (more than a million in a bucket of pond water or garden soil)

Slender, unsegmented, with tapering ends Most microscopic, but can be more than 1 meter

in length Free-living or parasitic

Respiration and Circulation occur through simple diffusion

Some cephalization - simple brain in head region

Many types have separate males and females (only some are hermaphroditic)

Fertilization is internal

Live in soil, salt flats, aquatic sediment, and water (from polar regions to tropics)

Eat microscopic animals, fungi, algae, bacteria, or detritus (dead leaves)

Have a tube-like digestive system with two ends: mouth and anus

Source

Although most roundworms are free-living, the parasitic roundworms are most well known

Examples include Trichinosis-causing roundworms, filial worms, ascarid worms, and hookworms

Trichinosis causes severe pain as the worms burrow through the tissues

Filial worms spread from host to host by biting insects (mosquitoes)

Live in blood and lymph tissues of the host which may lead to elephantiasis (lymph vessels are blocked by too many worms)

Ascaris lumbricoides is found in more than 1 billion people worldwide, leading to malnutrition

Live in the intestine and/or bloodstream of the host

Ascarid worms may reach up to 50 cm in length! (Link to convert to inches = http://www.worldwidemetric.com/metcal.htm)

25% of the world’s population is affected

Found in the soil, they use their sharp hooks and teeth to burrow into the skin and enter the bloodstream

They then travel to the lungs and then to the small intestine where they stay as adults.

Ancylostoma duodenaleNecator americanus

http://www.dpd.cdc.gov/DPDx/HTML/Para_Health.htm

Please choose from one of the categories belowor from the alphabetical listing at left.