The GastropodsPhylum Mollusca

Class Gastropoda – “Stomach Foot”

-Extremely diverse and numerous group of animals-Many are snails, but there are species without shells or without coiled shells

Examples:• Whelk – can be large, predators• Conch – can be large, wind instruments• Periwinkle – very common snail in our area• Nudibranchs – no external shell (interior one

made of protein)• Limpets – not coiled like most snails; conical

or relatively flat• Slipper Snail – can change from male to female• Abalone – used for jewelry

Anatomy• Most have a spiraling shell

surrounding a soft bodied animal

• Well defined head, ganglia, no hearing

• Excellent sense of smell/taste

• Gills to take oxygen from water

• Trap door (operculum) to protect animal when withdrawn in its shell

• Mantle secretes the shell• Bilateral symmetry

Habitat• Benthic– Motile– Epifauna –live on

seafloor– Have adapted to

almost every marine environment in the world (i.e., rocks, sand, mud, etc.)

Feeding-Most are scavengers using radula to scrape algae off rocks or decaying animal matter from the bottom-Some are predators

Ex: cone snailhttp://www.youtube.com/watch?v=zcBmMPJrrKk

Feeding cont.Some of predatory snails feed by drilling a hole in another MolluskExamples: moon snail, oyster drill

Radula in Action

Gastropod Reproduction

-Separate sexes-External fertilization and development-Distinct egg cases

Nudibranchs - Sea Slugs• Most brightly

colored to ward off predators

• Many have little outgrowths that are part of their respiratory system

Snail Internal Anatomy