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Phylum Annelida Leech Segmented Worms Fireworm Christmas tree worm Feather duster worm Annelid Characteristics • Segmentation = Metamerism – metameres (=somites, segments) – Show true segmentation - both internal and external – Allows for specialization Annelid Systems All systems found in Annelids but skeletal • Complete digestive tract - some specialization - crop and gizzard • Closed circulatory system - is segmentally arranged dorsal and ventral vessels aortic arches (hearts) Annelid Systems All systems found in Annelids but skeletal • Excretion – Nephridia segmentally arranged Annelid Systems All systems found in Annelids but skeletal • Nervous system – ladder shaped – pair of cerebral ganglia – double ventral nerve cords – pair of ganglia in each segment – several sensory structures • • • • taste buds tactile organs eyes in some statocyst Annelid Systems • Reproduction – some are monoecious, others dioecious – marine species have trochophore larvae – some have asexual reproduction by • Budding • fragmentation Annelid Systems • Respiration – across body surfaces – some have gills – some use parapodia Class Polychaeta • Make up 2/3 of phylum • most primitive annelids; ancestral to other two classes • almost all are marine, few freshwater species Polychaet Characteristics • differentiated head – Tentacles – first segment • Prostomium • Peristomium • Mouth – Palps – eyes Polychaet Characteristics • Parapodialateral appendages – notopodiumdorsal – neuropodiumventral – acicula- rods • Respiration – By parapodia Polychaet Characteristics • Reproduction – sexes separate – no permanent gonads • • • • egg and sperm form from coelomic peritoneum pass out of nephridia or burst thru body wall fertilization is external in sea free swimming larva- trochophore Polychaet Ecological Types • free living- all are predators • tube dwelling- all are filter feeders – secrete their own tube – burrow into substrate Class - Oligochaeta • Terrestrial or Freshwater • No distinct head - but contains pro- and peri- stomium • Clitellum - present at all times – Used in copulation – Cocoon production Class - Oligochaeta • Reproduction – – – – – Monoecious Copulation Internal fertilization Eggs laid in cocoon no larval stage Class - Oligochaeta • Digestive system - well differentiated – mouth – pharynx – crop – gizzard – intestine - Typhlosole – Anus Class - Oligochaeta • Circulatory system – Closed – 5 pairs of aortic arches – Hemoglobin • Respiration – Body surface • Excretion – Nephridia Class - Hirudinea • • • • • Freshwater or terrestrial Have suckers Segmentation fixed (34 segments) Clitellum only during season Digestive tract – large crop – Anticoagulant • Medically important
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