1. Soft – bodied invertebrates Clams, Octopus, Snails
Phylum Mollusca
Soft – bodied invertebrates
Clams, Octopus, Snails

2. Characteristics Coelomates Trochophore larva (aquatic molluscs)
Divided into head – foot and visceral mass
Visceral mass contains the heart and organs for digestion, excretion, and reproduction
Coleom surrounds the heart

4. Mantle, epidermal tissue secretes the shell Gills
Calcium carbonate
Gills
Found within the mantle cavity
Most are bilaterally symmetrical
Nervous system
Pair of ganglia in head – foot and visceral mass
Radula

5. Phylum Mollusca Divided into 7 classes
Focusing on 3 classes
Gastropoda, one or no shell (snails)
Bivalvia, two shells with hinge (clams)
Cephalopoda, tentacles (octopus)

6. Snapshot of Mollusca Diversity

7. Class Gastropoda Largest and most diverse group Single shell Torsion
Larval development visceral mass twists 180 degrees in relation to the head
Brings anus, gills, and mantle cavity in the front
Allows adult to pull itself into the cavity when threatened

9. Moves by using wave – like motion of foot Open circulatory system
Hemolymph
Flows into hemocoel (blood cavity)
Separate Sexes but may be hermaphroditic

10. Class Bivalvia
Shell is divided into 2 halves (valves) and connected by a hinge
Close the shell by contracting is adductor muscles, open by relaxing them
Three layers secreted by mantle
2nd layer consists of calcium carbonate

11. Bivalvia Sessile (foot) Filter – feeders Nervous system
3 pr of ganglia (mouth, digestive system, foot)

12. Clams Bury in mud Siphons extend past shell
Cillia on the gills pull water in the incurrent sipon
Water/food particles pass over the mucus on the gills and food becomes trapped
Oxygen is absorbed
Water exits the clam through the excurrent siphon

13. Clam Anatomy

14. Separate sexes Freshwater clams Gametes are released into water
Trochophore larvae
Freshwater clams

15. Class Cephalopoda Head – foot
Specialized for free – swimming predatory life
Circle of tentacles from the head
Beak
Advanced nervous system
Lobes with nerve cells
Sensory system

16. Closed circulatory system Separate sexes
Rapid movement of materials
Separate sexes
Egg into juvenile without trochophore larva
Chromatophores

17. Squid/Cuttlefish
10 tentacles
Internal shell

18. Octopuses
8 tentacles

19. Chambered Nautiluses Retains external shell
Coiled and divided into series of gas – filled chambers
Soft – body moves forward as the organism grows
Buoyant