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Phylum Nematoda. The round worms. Public Health Image Library. 200,000 known species but scientists think there may be 100 times as many Abundant in marine and freshwater they are also found in soil and some are parasitic
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Phylum Nematoda The round worms
Public Health Image Library • 200,000 known species but scientists think there may be 100 times as many • Abundant in marine and freshwater they are also found in soil and some are parasitic • Nematodes found in soil are microscopic: a shovel-full of dirt can contain, on average, 1 million individuals
Gas Exchange: diffusion into and out of a fluid-filled cavity (pseudocoelom) • Circulation: Fluids circulate through pseudocoelom • Excretion: anus and excretory pore • Digestion/feeding: one-way digestive system • Reproduction: sexual, sexual dimorphism is present (differences between males and females) • Response to environment: Often parasites, mouths can be equipped with piercing organs called stylets • Movement: unlike the ‘worms’ you know, Nematodes have longitudinal muscles instead of circular
Trichinella sp. • results from eating undercooked pork • Guinea worm • Results from drinking water with larva in it • Filariasis (elephantiatis) • Spread by mosquitos in tropical areas