1. Ch. 27 Phylum Mollusca Soft bodies Soft bodies Internal or external shell Internal or external shell Body Plan w/ 4 parts: Body Plan w/ 4 parts: Foot Foot Mantle Mantle Shell Shell Visceral Mass Visceral Mass Bilateral symmetry Bilateral symmetry

2. Shell Mantle cavity Foot Gills Digestive tract Snail Early mollusk Clam Squid Figure 27–21 The Mollusk Body Plan

3. Molluscan Body Visceral mass: Organ systems Visceral mass: Organ systems Foot: movement and feeding Foot: movement and feeding Mantle: thin tissue layer covering the body Mantle: thin tissue layer covering the body Shell: made of calcium carbonate (secreted by glands in mantle) Shell: made of calcium carbonate (secreted by glands in mantle)

4. Mouth Shell Stomach Coelom Heart Nephridium Adductor muscle Anus Excurrent siphon Incurrent siphon Gills Mantle cavity Foot Intestine Mantle cavity Adductor muscle Figure 27–23 The Anatomy of a Clam

5. Feeding Herbivores, carnivores, filter feeders, detritivores, or parasites Herbivores, carnivores, filter feeders, detritivores, or parasites Use of a radula (scrape or drilling)or siphon ( suck water in and push out) Use of a radula (scrape or drilling)or siphon ( suck water in and push out)

6. Mollusk

7. Respiration Aquatic  Gills inside mantle cavity Aquatic  Gills inside mantle cavity Land  mantle cavity has large surface area lined w/ blood vessels (moist places) Land  mantle cavity has large surface area lined w/ blood vessels (moist places)

8. Circulation Open Circulatory System (simple heart w/ vessels and sinuses-saclike spaces) Open Circulatory System (simple heart w/ vessels and sinuses-saclike spaces) Slow-moving: snails/clams Slow-moving: snails/clams Closed (network of blood vessels) Closed (network of blood vessels) Delivers oxygen faster Delivers oxygen faster Faster-moving (need more energy) Faster-moving (need more energy) – octopi/squid (higher demand for Oxygen)

9. Excretion Nephridia tubes remove ammonia from blood and release to outside Nephridia tubes remove ammonia from blood and release to outside Clams and bivalves  simple: ganglia, nerve cords, chemical receptors, eyespots Clams and bivalves  simple: ganglia, nerve cords, chemical receptors, eyespots Octopi  complex: most intelligent invertebrates w/ highly-developed nervous system and brain Octopi  complex: most intelligent invertebrates w/ highly-developed nervous system and brain Response

10. Movement Mucus Mucus Foot Foot Jet Propulsion w/ siphon Jet Propulsion w/ siphon Snails: sexually by external fertilization Snails: sexually by external fertilization Free swimming larva stage (trocophore) Free swimming larva stage (trocophore) Tentacles: internal fertilization Tentacles: internal fertilization Some hermaphrodites Some hermaphrodites Reproduction

11. Phylum Mollusca 3 classes near shore 3 classes near shore Gastropoda- Snails and slugs Gastropoda- Snails and slugs Bivalvia-Two shelled Bivalvia-Two shelled Cephalopoda- Squid & octopi Cephalopoda- Squid & octopi

13. 1) Gastropods Examples: snails, whelks, slugs Examples: snails, whelks, slugs Shell-less or single-shelled Shell-less or single-shelled Muscular foot on ventral surface Muscular foot on ventral surface Foot acts as door Foot acts as door Some scrape algae from rocks (radula) Some scrape algae from rocks (radula) External fertilzation External fertilzation

14. Cone snail-radula w/ toxins

15. Mud Snail

16. Channeled Whelk

17. 2) Bivalves Two shells Two shells Byssal threads- protein fibers attaching to rocks/surfaces Byssal threads- protein fibers attaching to rocks/surfaces No head No head No radula No radula Adductor/abductor muscles to close/open valves. Adductor/abductor muscles to close/open valves.

18. Feeding Cilia form currents to fill body cavity with water Cilia form currents to fill body cavity with water Mucus traps food on the gills Mucus traps food on the gills

20. 3) Cephalopods Soft bodied mollusk. Soft bodied mollusk. Foot is divided into tentacles or arms. Foot is divided into tentacles or arms. Foot attached to head Foot attached to head Octopi, squids, cuttlefishes, and nautiluses. Octopi, squids, cuttlefishes, and nautiluses.

21. Cuttlefish Nautilus

22. Ecology of mollusks Some concentrate pollutants in their tisssue. Some concentrate pollutants in their tisssue. Scientists check levels of pollutants to monitor level in environment Scientists check levels of pollutants to monitor level in environment Never develop cancer Never develop cancer Research as to why can be very important Research as to why can be very important http://www.youtube.com/watch?v=FFOEZ h1Lbbg http://www.youtube.com/watch?v=FFOEZ h1Lbbg http://www.youtube.com/watch?v=FFOEZ h1Lbbg http://www.youtube.com/watch?v=FFOEZ h1Lbbg