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The segmented worms “annelus” - little ring ZOOLOG Y Southern Boone County High School Bill Palmer TYPICAL ANNELIDS • Segmented worms – Earthworms – Leeches – Bristleworms ANNELIDS-Characteristics • • • • • 12,000 species Tube-within-a-tube Structure Bilateral Symmetry Mouth and Anus Setae (tiny bristles) – Help annelids to move • Terrestrial, Marine, and Aquatic ANNELIDS-Characteristics • All have segments (Like stacked donuts) General characteristics • segmented body • each segment has paired excretory nephridia, nerves • closed circulatory system • nervous system with double ventral nerve cordganglia for brain • respire through skin or with gills • body wall with longitudinal and circular muscle • setae/ bristles in skin used for locomotion 3 variations in setae structure 3 classes of Annelida Class Polychaeta – mostly marine fanworms, bristle worms, tube worms Class Oligochaeta - earthworms Class Hirudinea - leeches Marine tubeworms, fanworms and bristle worms Most primitive class- have well developed anterior end (head) lots of variety and color in marine species Setae on parapodia Marine polycheate – bristle worm Bristle worms Fleshy parapodia Ciliated feathery tentacles for feeding tube Marine fanworm Feather duster worms ( Polychaetes) Filter feeder Feather Duster worms Giant tube worms ( 4 ft long) in ocean thermal vents Calcareous (limestone) tubes of marine annelids Earthworms are important Food chains Aerate soil Bloodworm - Marine species Lives in mud at ocean bottom Great fishing bait! Polychaeta worm larva – pelagic ( planktonic ) Branching nerves Polychaete larva the leeches parasites Segmentation evident Suction disk Leech Leech Leech 3 pairs of eyes The earthworms plus some freshwater species Flatworm meets Annelid Crime scene Scotland Earthworm gathering Fossil Polychaete worm Bristles and segmentation evident Spriggina fossil Precambrian segmented invertebrate Segmented body ( metamerism ) Trochophore larva- typical of some annelids Mollusca phylum also has trochophore Larvae… suggesting related evolution Wrap-ups • • • • • How many species of annelida are there? What are the characteristics of annelida? What are the three classes of annelida? List three reasons why earthworms are important. How are leeches used in medicine?
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