Mollusca

Mollusca Phylum

representative organisms

• Cephalopods (i.e. Octopus, Squids, Cuttlefish)
• Gastropods (i.e. slugs, snails, whelks)
• Bivalves (i.e. oysters, clams, cockles)

Characteristics

• Soft bodied
• Mantle
• Radula
• Open circulatory system (except octopus)
• Bi-lateral symmetry

Characteristics

• Body without cavity
• Gaseous exchange organs
• Reproduce sexually
• Muscular foot/tentacles
• Some protected by hard shell 

DISTINGUISHING characteristics

• Digestive system is complete
• Mollusks have mucus covered foot
• This allows the mollusk to move around

Habitat

• Live predominately in:
• Freshwater
• Terrestrial
• Rocky shores
• Coral reefs

Habitat

• Mud flats
• Sandy beaches
• Oceans
• Phylum Mollusca is the most diverse phylum
• This is why they can be found in various habitats

body plan

• Contain a thin layer of skin called the mantle
• Between soft body and mantle is the mantle cavity
• Contain gills
• Mantle protects the body
• If there is no shell, the body is comprised of several layers

Body System

• Type: Open circulatory system

Mode of reproduction

• Sexual reproduction
• Usually with male and female
• Some are hermaphroditic
• Aquatic environments: fertilization is external
• Terrestrial Environments: fertilization is internal

MOde of REproduction (Mussels)

• Mussels have 2 separate sexes (hermaphroditic)
• These bivalves reproduce by releasing eggs
• Males release sperm into the open water
• Which is drawn into the female through the siphons
• Fertilized eggs develop into microscopic glochidia.

Mode of reproduction (snails)

• Snails are also hermaphroditic
• One snail stabs the skin of another snail with a "Love Dart"
• Stimulates the other snail and sperm is transferred 
• Female snail then produces eggs internally
• They fertilize the eggs in each other; both will deliver eggs

MODE OF REPRODUCTION (Squid)

• Male squid produces a special arm: a hectocotylus
• Transfers sperm to the female pallial cavity
• Eggs produced internally
• Thousands of eggs can be produced at a time by one female
• The female dies from being weak after the hatching process

Value of mollusks

• Scientific study on squid for memory
• Source of calcium for some organisms
• Indicate condition of ecosystem
• Can be poisionous

Value of mollusks

• Sold and raised
• Shells are typically worn as jewelry
• Used for decorations