notes for Class Cephalopda for Zoology

1. Class: CephalopodaClass: Cephalopoda
(head-foot mollusks)(head-foot mollusks)
Cuttlefish, squids,
octopuses, and nautiloids
are examples of
cephalopods. They are
so named because their
head is situated directly
on top of their foot. The
foot is divided into
tentacles.
Cuttlefish

2. CephalopodsCephalopods
• The most complex mollusks and also the mostThe most complex mollusks and also the most
complex invertebrate.complex invertebrate.
• The mantle encloses everything except head andThe mantle encloses everything except head and
tentacles.tentacles.
• Mantle is very muscularMantle is very muscular
– Mantle acts as pump to bring large quantities ofMantle acts as pump to bring large quantities of
water into the cavity.water into the cavity.

4. CephalopodsCephalopods
• External shells are absent in all cephalopodsExternal shells are absent in all cephalopods
except?except?
– NautiloidsNautiloids

5. This is a chambered nautilus. Its foot is easily visible here
(divided into many tentacles). The arrow is pointing to a
leathery cover that works somewhat like an operculum,
closing the aperture when the animal is at rest or in
danger.

6. CephalopodsCephalopods
• Squids and cuttlefish have an internal shell thatSquids and cuttlefish have an internal shell that
is made of 3 layers with gas-filled spacesis made of 3 layers with gas-filled spaces
between each layerbetween each layer
• helps with buoyancy.helps with buoyancy.
– CuttleboneCuttlebone

7. Octopuses are the
most familiar
cephalopods. They
have eight arms, all
equipped with
powerful suckers, and
eyes capable of sight
that rivals our own.

9. Below: The eyes are
elevated and capable of
excellent vision, even in
the dark.
Above: The suckers on the
ventral surface of the arms are
used to capture and grip food,
which consists of crabs, lobsters,
and shrimp.

10. A female octopus stays with their eggs until they hatch,
then she dies. This hatchling is still with the unhatched
eggs from its clutch.

11. CephalopodsCephalopods
• Are the only mollusk to have a closed circulatoryAre the only mollusk to have a closed circulatory
system.system.
• This means blood is confined to vesselsThis means blood is confined to vessels
throughout its circuit around the body.throughout its circuit around the body.

12. The blue-ringed
octopus is considered
to the most
venomous animal in
the world,
Second is the box
jellyfish. Both
animals are native to
the Great Barrier
Reef of Australia.

13. Squids are also cephalopods. Instead of eight
arms, they have ten. They are fast swimmers.
The fins along the sides of their body facilitate
their ability to swim fast.

14. This giant squid was found
dead. This species lives at
great depths, perhaps
greater that one mile. An
adult has never been
collected or seen alive.

16. Cuttlefish are
very similar to
squids. Their
head is smaller
and their
tentacles are
shorter. Some
of them have
incredible color
patterns.

17. ReproductionReproduction
• Are DieciousAre Diecious
• Male and female look different.Male and female look different.
• Males consists of testes that produce sperm andMales consists of testes that produce sperm and
structures that encase sperm into packets calledstructures that encase sperm into packets called
spermatophoresspermatophores..

18. ReproductionReproduction
• Females produce large yolk eggs and surroundFemales produce large yolk eggs and surround
them with a gel-like case that hardens when it isthem with a gel-like case that hardens when it is
exposed to seawater.exposed to seawater.

19. ReproductionReproduction
• Males have a specialized tentacle calledMales have a specialized tentacle called
hectocotylus that is used to transfer thehectocotylus that is used to transfer the
spermatophores.spermatophores.

21. ReproductionReproduction
• The hectocotylus transfers the spermatophoresThe hectocotylus transfers the spermatophores
to the female’s mantle cavity near the oviduct.to the female’s mantle cavity near the oviduct.
• The eggs move out of the body through theThe eggs move out of the body through the
oviduct and then the mantle cavity and areoviduct and then the mantle cavity and are
fertilized in the oviduct.fertilized in the oviduct.

22. ReproductionReproduction
• The eggs are then attached to the substrate.The eggs are then attached to the substrate.

23. The chiton’s shell is divided into many
plates, hence the class name Polyplacophora,
“bearing many plates”.
Class: Polyplacophora - ChitonsClass: Polyplacophora - Chitons

24. THE
END