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MARINE WORMS

MARINE WORMS. Common Characteristics of All Worm Phyla. Hydrostatic skeleton Bilateral symmetry. Phylum Platyhelminthes - Flatworms. Dorsoventrally flattened – flat backs and bellies Have real organs and organ systems Ladderlike nerve cord with a simple brain

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MARINE WORMS

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  1. MARINE WORMS

  2. Common Characteristics of All Worm Phyla • Hydrostatic skeleton • Bilateral symmetry

  3. Phylum Platyhelminthes - Flatworms • Dorsoventrally flattened – flat backs and bellies • Have real organs and organ systems • Ladderlike nerve cord with a simple brain • Saclike digestive system (only one opening) • 15,000 species • Turbellarians – mostly free swimming carnivores • Flukes (trematodes) – all are parasites • Tapeworms (cestodes) – parasites with long segmented bodies

  4. Phylum Nemertea – Ribbon Worms • Long flattened bodies • Complete digestive tract (separate mouth and anus) • Circulatory system with blood • Proboscis – long fleshy tube used to entangle prey • 900 species, mostly marine

  5. Phylum Nematoda - Roundworms • Common in sediments or as parasites • Cylindrical body typically pointed at both ends • Complete digestive tract • 10,000-15,000 species but many could yet to be discovered

  6. Phylum Annelida – Segmented worms • 13,000 species • Complete digestive tract • Efficient crawlers and burrowers • Closed circulatory system – blood always remains in blood vessels (arteries, veins, capillaries) • Class Polychaeta • On each segment they have a pair of parapodia and setae (bristles) • Gills for respiration • 6000 species almost entirely marine

  7. 4 to 10 cm in length • Deposit or suspension feeders • Some are tube dwelling • Class Hirudinea – Leeches • Mostly freshwater • Suckers at each end • No parapodia

  8. Other Marine Worms • Phylum Sipuncula – Peanut worms • Peanut shaped, deposit feeders • Phylum Echiura • Sausage shape, buried in mud • Phylum Pogonophora – Beard Worms • Lack a digestive system, symbiotic relationship with bacteria for obtaining nutrients • Vestimentiferans found at hydrothermal vents • Phylum Chaetognatha – Arrow Worms • 60 species, but common in plankton, fishlike body, voracious carnivores

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