MOLLUSCA

Characteristics Class Gastropoda – snails, slugs Class Gastropoda – snails, slugs Class Cephalopoda – octopus, squid, nautilus Class Cephalopoda – octopus, squid, nautilus Class Bivalvia – oysters, clams Class Bivalvia – oysters, clams Soft body covered by shell (usually) Soft body covered by shell (usually) Bilateral symmetry Bilateral symmetry Word mollusca means “soft” Word mollusca means “soft”

Anatomy One way digestive system – mouth to anus One way digestive system – mouth to anus Coelomates Coelomates Open circulatory system in gastropods and bivalves- blood sloshes around body cavity Open circulatory system in gastropods and bivalves- blood sloshes around body cavity Closed circulatory system in cephalopods Closed circulatory system in cephalopods Gills for respiration on mollusks that live in water Gills for respiration on mollusks that live in water

Anatomy Mollusks have strong muscles to help them move and swim Mollusks have strong muscles to help them move and swim The skeleton of most mollusks is a shell, but not all mollusks have a shell The skeleton of most mollusks is a shell, but not all mollusks have a shell

Anatomy Gastropods and Bivalves have a simple nervous system and Cephalopods have a complex nervous system Gastropods and Bivalves have a simple nervous system and Cephalopods have a complex nervous system Mollusks cover their bodies with skin and shells. Most mollusks have to keep their skin moist. Mollusks cover their bodies with skin and shells. Most mollusks have to keep their skin moist.

Anatomy Mollusks all have a “foot”. In bivalves this is the soft inside of the clam. In gastropods, they use their foot to move along the ground. In cephalopods, the foot has been adapted to be the mantle. Mollusks all have a “foot”. In bivalves this is the soft inside of the clam. In gastropods, they use their foot to move along the ground. In cephalopods, the foot has been adapted to be the mantle.

Anatomy All mollusks have a full excretory system. A snail’s anus is located right over it’s head and it poops right onto itself. Squid and octopi excrete waste out of the mantle as they swim. All mollusks have a full excretory system. A snail’s anus is located right over it’s head and it poops right onto itself. Squid and octopi excrete waste out of the mantle as they swim.

Feeding Radula – rough tongue or ribbon of teeth Radula – rough tongue or ribbon of teeth Herbivores, scavengers, carnivores, omnivores Herbivores, scavengers, carnivores, omnivores

Reproduction All mollusks reproduce sexually All mollusks reproduce sexually Both males and females Both males and females

Habitat Terrestrial Terrestrial Marine Marine Freshwater Freshwater Rocky shores Rocky shores Niche? Niche? Biotic factors? Biotic factors? Abiotic factors? Abiotic factors?

Adaptations Cephalopods need to swim very fast so have closed circulatory system Cephalopods need to swim very fast so have closed circulatory system Bivalves have flattened shape and strong foot to hold on in intertidal zones Bivalves have flattened shape and strong foot to hold on in intertidal zones Shells for defense Shells for defense

Gastropods Largest group of mollusks Largest group of mollusks “stomach foot” “stomach foot” 0 to 1 shell 0 to 1 shell Movement on foot – slippery mucus Movement on foot – slippery mucus radula radula

Bivalves 2 shells held by hinge 2 shells held by hinge No radula – filter feeders No radula – filter feeders Mostly sessile Mostly sessile Grain of sand that gets stuck between mantle and shell causes bivalve to produce mucus – pearl Grain of sand that gets stuck between mantle and shell causes bivalve to produce mucus – pearl Found in all water environments Found in all water environments Omnivores Omnivores

Cephalopods “Head foot” “Head foot” Ocean dwelling Ocean dwelling Foot forms tentacles around mouth Foot forms tentacles around mouth Carnivores with radula Carnivores with radula Swim by jet propulsion Swim by jet propulsion Most complex nervous system of all invertebrates Most complex nervous system of all invertebrates Nautilus-external shell Nautilus-external shell Squids-small internal shell Squids-small internal shell Octopus- no shell Octopus- no shell