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Annelida Polychaeta Larva = Trochophore Band of cilia around body; tuft on apex

Annelida Polychaeta Larva = Trochophore Band of cilia around body; tuft on apex Same larval stage in Mollusca, Echiura, Sipuncula Diverse lifestyles Free-living predators Often well-developed eyes and sense organs, jaws Burrowing deposit feeders Burrowing suspension feeders

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Annelida Polychaeta Larva = Trochophore Band of cilia around body; tuft on apex

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  1. Annelida • Polychaeta • Larva = Trochophore • Band of cilia around body; tuft on apex • Same larval stage in Mollusca, Echiura, Sipuncula • Diverse lifestyles • Free-living predators • Often well-developed eyes and sense organs, jaws • Burrowing deposit feeders • Burrowing suspension feeders • Tube building suspension feeders • Tubes may be calcium carbonate, agglutinated or parchment • Solitary • Colonial

  2. Annelida • Oligochaeta • Few marine species • Small organisms • Benthic – mud and sand • Deposit feeders • No parapodia • Hirudinea (Leeches) • Few marine species • Parasitic • No parapodia

  3. Mollusca • More species (200,000+) than any other animal phylum except Arthropoda • Soft body • Unsegmented, typically bilaterally symmetrical • Often protected by calcium carbonate shell • Mantle secretes shell • Ventral muscular foot • Many with head bearing eyes, sensory organs • Radula – Ribbon of small chitin teeth used in feeding • Gills for gas exchange • Many permutations on basic plan • Bivalves lack radulas • Squids have internal shells • Octopuses have no shells

  4. Fig. 7.19

  5. Mollusca • Gastropoda (Class) • Largest, most common, most diverse group • Snails • Limpets - Territorial • Abalones • Nudibranchs – Some store elements of diet • Shell often coiled (Exceptions ?) • Ventral creeping foot • Diet • Many vegetarian (scrape algae off rocks with radula) • Some predatory • Prey on bivalves, worms, fishes, sponges

  6. Nudibranchs with symbiotic algae

  7. Fig. 7.20 Glaucus atlanticus

  8. Mollusca • Bivalvia • Laterally compressed • Two-valved shell • No head • No radula • Some have muscular foot for burrowing (How?) • Gills used for suspension feeding (active) & respiration • Water enters and leaves through siphons • Some anchor to substrate with byssal threads • Largest mollusk (giant clam) • Shipworms (boring – use shells as rasps) • Common fouling organisms • Oysters – Produce pearls • Scallops – Swim!

  9. Fig. 7.22

  10. Mollusca • Bivalvia • Laterally compressed • Two-valved shell • No head • No radula • Some have muscular foot for burrowing (How?) • Gills used for suspension feeding (active) & respiration • Water enters and leaves through siphons • Some anchor to substrate with byssal threads • Largest mollusk (giant clam – Tridacna gigas) • Shipworms (boring – use shells as rasps) • Common fouling organisms • Oysters – Produce pearls • Scallops – Swim!

  11. Tridacna gigas Geoduck Video Geoduck

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