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Phylum Nematoda : Roundworms. 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. Roundworm Body Systems.
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Phylum Nematoda: Roundworms • 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
Roundworm Body Systems • 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
Free-Living Roundworms • 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
Parasitic Roundworms • 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 • Trichinosis causes severe pain as the worms burrow through the tissues
Filial Worms • 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)
Ascarid Worms • Ascarislumbricoides 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)
Hookworms • 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
Great Website on Parasites • http://www.dpd.cdc.gov/DPDx/HTML/Para_Health.htm