33 Class Oligochaeta Oligochaetes are largely freshwater (small species) or terrestrial (earth-worms); they lack parapodia, and have very few setae per segment; earthworms have reduced heads and evidence of cephalization. Most are scavengers, feeding on dead organic matter, especially vegetation. Small freshwater species feed on detritus and microorganisms. They have a clitellum and are hermaphroditic . Sketch a typical oligochaete in the space to the right. What is the function of the clitellum? Class Hirudinea Leeches are largely fresh water, but have damp terrestrial members also. They lack the internal septa, are dorsoventrally flattened , have lobed intestines (which swell when they feed), and (like oligochaetes) possess a clitellum and are hermaphroditic . Leeches lack setae, which are characteristic of the other two classes. Most leeches are intermittent ectoparasitic blood feeders, but some are predators or scavengers. The anterior sucker is reduced, but the posterior sucker is conspicuous. Eyes
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