1. Mollusks

2. Mollusk Vocabulary Word Definition foot mantle siphon
An appendage that some invertebrates use to move.
mantle
A layer of tissue that covers the body of many invertebrates; secretes a shell.
siphon
A hollow tube of mollusks, used for sucking in and expelling sea water.

3. What is a Mollusk?
Photo credit: NOAA

4. Characteristics Soft-bodied coelomates 3 part body plan Visceral mass
Mantle
Foot
Bilateral symmetry
MOST have a shell

5. Mollusk Body Plan
Visceral mass: central section of a mollusk’s body  contains the organs

6. The Mantle
Layer of tissue that covers the body of many invertebrates: secretes a shell
Univalve: 1 shell
Bivalve: 2 shells
Photo credits: MSC

7. The Foot
Muscular region; used for movement

9. Organ Systems: Digestion
Clams (filter feed)
All mollusks (except bivavles) have a radula.
Radula – a rasping, tonguelke organ that is covered with “teeth”; used for feeding by many mollusks

10. Circulation & Respiration
3 chambered heart
Most mollusks breathe with gills
Open circulatory system
Terrestrial snails – membrane that lines the snail’s mantle = basic lung
Octopi – closed circulatory systems
Some sea snails = diffusion through skin

11. Reproduction Male & female individuals Snails & slugs = hermaphrodites
Fertilized eggs of most mollusks  trochophore
Trochophore – free-swimming ciliated larvae

12. 3 Major Mollusk Classes

14. Gastropods – (Snails & Slugs)
Marine, freshwater, & terrestrial habitats
Pair of tentacles on their head – eyes at the tips
Mucus comes from their foot – glide along
Use radula to scrape off food

15. Cephalopod – “head foot”
Foot = tentacles (w/ suction cups or hooks)
Squids = 10, octopi = 8
Most intelligent of all invertebrates
Complex nervous system
Siphon – “jet propulsion”, also release “ink”
What are CHROMATOPHORES!?
Ex: Octopus, squid, nautilus

16. Bivalves Two-part, hinged shell Flattened body between two shells
Most are filter feeders (gills to filter food)
Pearl Production – grain of sand gets stuck betweent he mollusk’s mantle & shell
Coat with nacre (mother-of-pearl); shiny substance
Ex: Clams, oysters, scallops, mussles