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Mollusk Life Cycle

Mollusk Life Cycle. Most mollusks are dioecious (separate sexes) Some are hermaphroditic The life cycle of many mollusks includes a free swimming, ciliated larval stage called a TROCHOPHORE. Major Mollusk Classes. Four major classes of mollusks: Class Polyplacophora – the chitons

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Mollusk Life Cycle

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  1. Mollusk Life Cycle • Most mollusks are dioecious (separate sexes) • Some are hermaphroditic • The life cycle of many mollusks includes a free swimming, ciliated larval stage called a TROCHOPHORE

  2. Major Mollusk Classes • Four major classes of mollusks: • Class Polyplacophora – the chitons • Class Gastropoda – snails & slugs • Class Bivalvia – clams, mussels, oysters • Class Cephalopoda – octopus & squid

  3. Class Polyplacophora • Includes the chitons • Eight overlapping shell plates • Can roll up • All marine • Use radula to scrape algae off rocks.

  4. Class Gastropoda • largest of the mollusk classes • 70,000+ named species • Include snails, slugs, nudibranchs (sea slugs), sea butterfly • Marine, freshwater, terrestrial • Creep along using foot

  5. Class Gastropoda • The shell of a gastropod is always one piece, called a valve. • Gastropods are considered univalves

  6. Class Gastropoda • Many snails can withdraw into the shell and close it off with a lid called an operculum.

  7. Class Gastropoda • Nudibranchs are sea slugs • Do not have shell • Have colorful branches of gut or gills exposed • Prey on sponges, cnidarians, & other invertebrates • May produce noxious chemicals

  8. Class Gastropoda- Nudibranchs

  9. Class Gastropoda- Nudibranchs

  10. Gastropod Feeding Habits • Most gastropods are herbivores and feed by scraping algae off of rocks using the radula. • Some (like nudibranchs) are carnivores

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