Cephalopodes are advance molluscs-Among Mollusca, Cephalopodes are the highly specialized and advanced group.

2. Introduction
• Among Mollusca, Cephalopodes are highly specialized and
advanced group.
• The advanced characters are the following:

3. Morphology
• Look like vertebrates
• Body distinctly into three regions(head, neck, trunk)
• Eg: Spepia, Loligo

4. Head
• The head is large globular and
prominent like vertebrates.
• It bears tow large eyes,
tentacles, a mouth and a funnel

5. Eyes
• The head bears two large eyes like vertebrates. The eye
posses an orbit, a sclerotic coat, a retina, the rods, a cornea,
a lens, an iris, a cilliary body, the aqueous membrane, the
vitreous humours, etc.

6. Colour change
• The skin of cephalopodezs contains
chromatophores and iridocytes.
• It contains colour pigments such as red, yellow
and orange.
• The pigments can be concentrated or
disappeared producing different shades of colour
for protection.

7. Shell
• In Sepia and Loligo, the shell is internal. It forms a
short of endoskeleton as in the case of vertebrates.

8. Digestive system
• Digestive system is well developed.
• It formed of a mouth, lips,jaws, a buccal
cavity, an oesophagus, a stomach, an
intestine, a rectum and an anus.
• The three major types of digestive glands
are present
• Salivary gland, the pancreas and liver(like
vertebrates)

9. Locomotion
• Sepia and Loligo –move backward & forward
• Swim- by wings
• Eject out water through the siphon.
• Siphon is directed forward the animal is propelled
backward.

10. Ink gland
• Have ink gland
• Secrete a dark ink for protection.
• When attacked by an enemy, it liberates the ink into
the water producing a smoke-screen and the enemy
is confused.

11. Nervous system
• Well developed
• It forms of ganglia, commissures,
connectives and nerves.
• have a special type of star shaped
ganglia in the mantle, called stellate
ganglia.
• The brain is enclosed in a cranial
cartilage

12. Circulatory & excretory system
• Closed type
• Arteries and veins are connected by capillaries
• Have two type of heart
-arterial heart
-venous heart
Carried out by kidney
Excretory product is in the form of guanine

13. Reproduction & copulation
• Sexes are separate
• Male –have modified tentacle
called hectocotylized arm.
• This arm inserted into femal
mantle cavity.
• He deposits spermatophores
in the funnel of the female
safety.

14. Development
• Fertilization is internal
• Fertilization egg is enclosed in a capsule
• The eggs are larger in size and are heavily loaded
with yolk.
• The eggs are made into bunches and are attached to
sea-weeds.
• Development is direct.