The gastropods are an extremely diverse class of mollusks that includes snails and slugs. While many have coiled shells, some have no external shell at all. They have a well-defined head and lack ears, but have excellent senses of smell and taste. Gastropods are found in nearly every marine habitat and feed by scraping algae and decaying matter using a rasping tongue called a radula. Reproduction involves external fertilization and development of egg cases.

1. The Gastropods
Phylum Mollusca

2. Class Gastropoda – “Stomach Foot”
-Extremely diverse
and numerous group
of animals
-Many are snails, but
there are species
without shells or
without coiled shells

3. 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

4. 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withdrawn in its shell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

5. Habitat
• Benthic
– Motile
– Epifauna –live on
seafloor
– Have adapted to
almost every
marine
environment in the
world (i.e., rocks,
sand, mud, etc.)

6. Feeding
-Most are scavengers
using radula to
scrape algae off rocks
or decaying animal
matter from the
bottom
-Some are predators
Ex: cone snail
http://www.youtube.
com/watch?v=zcBm
MPJrrKk

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

8. Radula in Action

9. Bivalve Reproduction
-Separate sexes
-External
fertilization and
development
-Distinct egg
cases

10. Nudibranchs - Sea Slugs
• Most brightly
colored to
ward off
predators
• Many have
little
outgrowths
that are part
of their
respiratory
system

11. Snail Internal Anatomy