BI 173 - Chapter 22 - Annelids.  Segmented Worms.

    Bilateral Symmetry

        Cephalization - "Brain," senses.

    Metamerism / Segmentation. Between front & back segments.

         Usefulness.

        Fluid-filled Chambers.

            Hydrostatic Skeleton.

        2 "Opposed" Muscle Layers.

        Setae: Sometimes on Parapods.

    Closed Circulation w/ segmented characteristics.

        Respiratory carriers in blood.

     Surface respiration, sometimes gills.

        Thin, permeable cuticle.

    Segmented nephridia. Open tubes w/ reabsorption.

    Double Ventral Nerve Cord.

        Segmented. Paired Ganglia.

    Digestive System - One-Way tube, non-segmented.

    Sexual, w/ monoecious or dioecious species.

        Trochophore Larva common.

    Polychaete Worms. Marine worms, tubeworms, fanworms, etc.

        Mostly marine. Small, all sorts of niches.

        Important in food chain & materials/sediment recycling.

    Oligochaete Worms.

        FW - somewhat similar to marine worms.

        Terrestrial - Earthworms.

    Leeches. Hirudinea.

        Always same # segments as adults - usually 34.

         Segmentation lessened internally.

        Mostly Predators.

            Some facultative parasites.

            Few obligate parasites.

Michael McDarby,
        Based Upon Hickman-Roberts-Larson Biology of Animals,
            1998, WCB McGraw-Hill.
        Internet Version Uploaded 2001.