BIOL 1010 Lecture Notes - Lecture 45: Gastrovascular Cavity, Flatworm, Cestoda
14 May 2017
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Flatworms from phylum platyhelminthes (platys flat, helmis. Worm) are the simplest bilaterians: thin, ribbon-like range from in length from 1mm-20m. o live in marine, freshwater, & damp terrestrial habitats. o. Free-living forms, many are parasitic species: flatworms have gastrovascular cavities with only one opening (same as cnidarians). Fine branches of the gastrovascular cavity distribute food throughout the animal. A planarian has a head with a pair of sensitive eye-cups & flap at each side that detects chemicals. Dense clusters of nerve cells form a simple brain, & a pair of nerve cords connects with small nerves branching throughout the body. When it feeds, it sucks food through the mouth at the tip of a muscular tube projecting from the mid-ventral surface of the body. They live on the undersurface of rocks in freshwater ponds. When searching for food, they crawl using cilia on their ventral surface. They also have muscles used to twist & turn.
