HELMINTHS These are the parasitic worms. They belong to two phyla, Platyhelminthes (flatworms) and Nematoda (round worms). Both phyla contain many free-living species, but only the parasitic species will be discussed. Helminths are multicellular eukaryotic animals. They generally have digestive systems, circulatory systems, nervous, excretory, and reproductive systems. Parasitic helminths must be highly specialized to live within their hosts. Compared to free-living helminths, the parasitic forms: 1. May lack a digestive system, and live by absorbing nutrients from the food, body fluids and tissues of the host. 2. 2. May have a reduced nervous system, because they do not have to search for food or respond much to their environment.
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