1) Cephalopods such as octopuses, squid, and cuttlefish have adapted for life in the water through mechanisms like buoyancy control, shell reduction, and specialized cells and organs. 2) They possess acute sensory abilities, speed that rivals fish, and intelligence with large brains relative to body size. 3) Defenses include camouflage through chromatophores and iridophores that can change skin color and patterns rapidly, as well as ink secretions.

1. Best understood in the context of their
largely sedentary adult life style

2. ctenidium umbo
Excurrent
Incurrent
siphons
Adductor
muscle
Foot Mantle edge
Labial
palps
mouth
Right
valve

3. Ctenidia of Bivalves are modified for feeding
except in one group: the Protobranchs

4. In most bivalves ctenidia are sheet-like
with high S.A., and are used for feeding

5. The sheetlike, arrangement of ctenidia in most
bivalves is known as the Llamellibranch condition
Summary of Water Flow and Feeding
http://web.uconn.edu/jevanward/video/musselsum.MPG

6. There are two basic type of
Llamellibranch ctenidia in bivalves
Filibranch
(in mussels)
Eullamellibranch
(most clams)

7. Living Cephalopods
Octopods
Cuttlefish
Nautilus
--The class as a whole is adapted for
swimming, suspended in the water by
buoyancy mechanisms.
Squid
-- all are carnivores, occupying the same niche as fishes

8. Ammonites
Largest is 3 m in
diameter

9. Sub Class Nautiloidea
5-6 species remain from
diversity in geologic past
Live in the last chamber of
a multi-chambered shell
Move by forcing water
through a siphon.

10. Sub Class Nautiloidea
How does a Nautilus adjust and maintain
its buoyancy in water?

11. Cuttles, Squids and Octopuses
-tendency is reduction of shell.
- compensated for by selective
ionic control; accumulate ammonium
- other adaptations to shell loss
and life style

12. Specifically, compensation takes the
following forms:
Stealth and other defenses
Acute sensory structures
Speed
Cunning

13. Ink Sack : ink with melanin and mucus
also dopamine, L-DOPA, tyrosinase
A. Stealth and other defenses
Pseudomorphs

14. A. Stealth and other defenses
Chromatophores: each cell contains a different pigment
which may be red, orange, brown, black, yellow or blue

15. Cephalopod Chromatophore
neurophilosophy.files.wordpress.com
Black, brown, orange or yellow colors
Also iridiophore reflective cells
Most cephalopods are completely colorblind
9/16/2004 11:42 AM
The most well known of these cells is the chromatophore. Chromatophores are
groups of cells that include an elastic saccule that holds a pigment, as well as 15-25
muscles attached to this saccule (Hanlon and Messenger 1996). These cells are located
directly under the skin of cephalopods. When the muscles contract, they stretch the
saccule allowing the pigment inside to cover a larger surface area. When the muscles
relax, the saccule shrinks and hides the pigment. Unlike other animals, the
chromatophores in cephalopods are neurally controlled, with each chromatophore being
attached to a nerve ending (Messenger 2001). In some squid, each chromatophor muscle
is innervated by 2 to 6 nerves that directly link to the animals brain (Messenger et al
2001).
In this way the animal can increase the size of one saccule while decreasing the
size of another one right next to it. This allows the cephalopods to produce complex
patterns (Messenger 2001, Messenger et al 2001), such as the zebra stripes seen in
aggressive displays by male cuttlefish. The speed at which this can be controlled allows
the animal to manipulate these patterns in a way that makes them appear to move across
the body. In some species of cuttlefish, it has been noted that while hunting, the cuttlefish
may produce a series of stripes that move down their bodies and arms. Some scientists
have suggested that this could be used to mesmerize prey before striking, but the purpose
of this behavior has yet to be proven. The pigments in chromatophores can be black,
brown, red, orange or yellow. They are not responsible for producing the blue and green
colors seen in some species. Interestingly, many deep water forms possess fewer
chromatophores as they are less useful in an environment in little or no light.
Figure 2. A) Chromatophores on skin of Loligo. (CephBase image No. 280 by Roger T. Hanlon) B)
Chromatophores visible on Lolliguncula brevis (CephBase image No. 263 from UTMB).
Iridophores are found in the next layer under the chromatopphores (Hanlon et al
1990, Cooper et al 1990). Iridophores are layered stacks of platelets that are chitinous in
some species and protein based in others. They are responsible for producing the metallic
looking greens, blues and golds seen in some species, as well as the silver color around
the eyes and ink sac of others (Hanlon and Messenger 1996). Iridophores work by
reflecting light and can be used to conceal organs, as is often the case with the silver
coloration around the eyes and ink sacs. Additonally they assist in concealment and
communication. Previously, it was thought that these colors were permanent and
unchanging unlike the colors produced by chromatophores. New studies on some species
of squid suggest that the colors may change in response to changing levels of certain
hormones (Hanlon et al 1990, Cooper et al 1990). However, these changes are obviously
slower than neurally controlled chromatophore changes. Iridophores can be found in
cuttlefish, some squid and some species of octopus.

16. -- Vision
-- Lateral line analogs
B. Acute sensory structures

17. Rival fish in ability to swim, attaining
burst speeds of 5-10 m second sustained
for short distances at speeds of up to 40 km hr.
Burst speed is achieved by jet propulsion
More gradual swimming is fin undulation
C. Speed

18. complex nerve control
of locomotion
C. Speed :
Assures synchronized contraction of mantle muscles

19. Requires a
closed,
elaborate
circulatory
system
Hearts
C. Speed : circulatory system

20. D. Cunning
-- Relative to body size, the
brain is larger than that of
most fish