The document discusses bivalve mollusks such as mussels, clams, oysters, and scallops. It defines key anatomical features including the umbo, pallial line, and adductor muscles. The foot of bivalves is described as extendable and used for digging or swimming. Scallops swim by clapping their shells together. Zebra mussels were introduced accidentally to North American waters and have become an invasive species, costing millions in damage by clogging water intake pipes. Bivalves play an important ecological role which has been disrupted by zebra mussels in some areas.

1. Phylum: MolluscaPhylum: Mollusca
Class: BivalviaClass: Bivalvia
Mussels, Clams, Oysters, ScallopsMussels, Clams, Oysters, Scallops

2. Class: BivalviaClass: Bivalvia
(bivalved mollusks)(bivalved mollusks)
Scallops are an example of a
bivalve. Bivalves have two
valves (hinged halves to their
shells).
Their foot is extendable and it
looks like a tongue. It is
normally used for digging,
allowing the animal to bury itself.
Not all bivalves dig.

3. This photograph shows the important anatomical structures of
a bivalve mollusk.
umbo

4. Important WordsImportant Words
• UmboUmbo – is the oldest part of the shell, on the– is the oldest part of the shell, on the
dorsal side of the shell (the point).dorsal side of the shell (the point).
• Pallial LinePallial Line – is the scar where the mantle– is the scar where the mantle
attached.attached.
• Adductor MusclesAdductor Muscles – are the muscles that hold– are the muscles that hold
the valves closed and leave scars on the anteriorthe valves closed and leave scars on the anterior
and posterior end.and posterior end.

5. umbo

6. foot
The foot of this clam
is in the extended
position. The tip is
bent as it searches for
sand or mud into
which it can dig and
pull its entire body,
shell and all, beneath
the sea floor.
mantle

7. This scallop’s valves are slightly open. The white tissue on the
inside is the mantle. The dark dots are the eyes. Notice the
thread-like structures extending from the mantle. Scallop use
these for protection. They extend them to entangle predators.
The threads can detach while the scallop swims away.

8. This scallop is swimming. It does so by clapping its valves
together. The foot is visible at the top of the picture and the
threads are extended. If a potential predator touches those
threads it will become entangled in them and they will break
off of the scallop.

9. These are zebra
mussels, a European
bivalve that was
accidentally
introduced into the
Great Lakes by cargo
ships from Europe.
Fishing boats from Lake Erie have accidentally carried
zebra mussel larvae to other Ohio bodies of water,
including the Ohio River. This species has become a major
conservation issue. It is costing Ohio residents millions of
dollars per year in damage. Zebra mussels invade Ohio
only ten years ago.

10. Zebra mussels
reproduce so fast that
in ten years their
populations have
grown large enough to
clog the intake pipes
for Cleveland and
Toledo’s water
supplies. They also
clog water intakes for
power plants.
Almost all freshwater clams are now
extinct in western Lake Erie. Zebra
mussels rob them of their food
supply. This has taken only ten years.

11. Types of BivalvesTypes of Bivalves
• OystersOysters- are very asymmetrical- are very asymmetrical

12. Types of BivalvesTypes of Bivalves
• ClamsClams- shells have ridges- shells have ridges

13. Types of BivalvesTypes of Bivalves
• MusselsMussels- dorsal ventral is longer than anterior- dorsal ventral is longer than anterior
and posterior.and posterior.

14. Types of BivalvesTypes of Bivalves
• CocklesCockles- valves look like a heart- valves look like a heart

15. Types of BivalvesTypes of Bivalves
• ScallopsScallops- have wings on the umbo (looks like the- have wings on the umbo (looks like the
symbol of shell gas station)symbol of shell gas station)

16. THE
END