Cephalopods
Corresponding Reading Material
~ Squid section in Lab
Manual
~ Levinton: Chapter 8
The Phylum Mollusca
General Characteristic:
1. Bilaterally symmetrical
2. Possess a mantle which secretes the shell
3. muscular foot
4. radula (file-like feeding structure); modified in some
classes
5. Possess a one way gut
6. Reproduces sexually
There are 7 different classes within the mollusk phylum:
~ Class Polyplacophora - Chitons
~ Class Aplacophora - Mollusks without shells
~ Class Monoplascophora - Mollusks with one shell
~ Class Schapoda - Mollusks with a tubular shell
~ Class Gastropoda - Gastropods, snails and their relatives
~ Class Bivalvia - Bivalves
~ Class Cephalopoda - Cephalopods, squids and octopuses
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The Class Cephalopoda
Are the most highly evolved mollusks and invertebrates.
General Characteristics:
1. A funnel derived from the molluscan foot
2. Chitinous beaks
3. Complex eyes.
4. Have a head surrounded by a foot divided into arms
5. Are carnivorous
6. Well organized nervous system
7. Have complex behaviors
Cephalopod Evolution
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The earliest cephalopods were shelled mollusks that were probably similar
to limpets. They appeared 500 million years ago during the Upper
Cambrian Period.
The ammonite with its coiled shell appears in the Devonian period around
400 mya same time as sharks). This organism shows a great
advancement in mobility. Ammonites continued with numerous
developmental variations and became the dominant cephalopod until the
end of the Cretacious period about 144 mya.
The driving force of the extensive evolutionary change seems to be
related to the changes in the continental configuration between 500 and
140 mya. These changes brought about severe alterations in climate,
major reconfigurations of continental shelves, reduction in estuaries and
wetlands, and changes in oceanic current patterns.
The Nautilus
The nautilus is different from many of the other
cephalopods because it has retained its shell.
The Diversity of Cephalopods
Today there are approximately 650 different species of cephalopods.
Ecology of Cephalopods
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Cephalopods are strictly marine. They usually live in the deeper waters of
the ocean, but some species are known to live in shallower waters.
They are found from the warm waters of the tropics to the near freezing
waters by the poles.
Most species are nektonic (live in the water column far above the sea floor)
All cephalopods are predators. They use tentacles to capture prey, and they
have beaks that tear apart the flesh.
The Blue Ring
Octopus
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bdxg
It lives in warm,
shallow reefs off the
coast of Australia,
New Guinea,
Indonesia, and the
Philippines.
It has a life span of
about 1.5 years.
The Blue Ring Octopus is the
most venomous octopus.
It catches prey with its
arms, bites it with its tough
beak, and kills it by
delivering a poison in the
saliva. The poison is a
neurotoxin that is strong
enough to kill a human.
The Giant Pacific Octopus
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largest species of octopus in the world.
Most individuals weigh less than 100 lbs
but an individual captures near Victoria,
British Columbia in 1967 weighed 156
lbs. and was almost 23 ft from arm tip to
arm tip.
mainly lives on the continental shelf of
the north Pacific ocean.
After hatching, the Giant Pacific Octopus
swims towards the surface and spends 412 weeks drifting in the plankton until it
reaches a size of >14mm.
They typically live 3-5 years.
The Giant Squid
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the largest invertebrate to ever live on
Earth. No one has ever seen a giant squid
alive in its own habitat.
Scientists know of their existence through
the study of specimens found in the
stomachs of sperm whales, washed up on
beaches, or caught in fishermen’s nets.
can grow up to 21.3m (70ft.) long. Their
arms alone can grow to be 10 feet long
while their tentacles can extend as far out
as 36 feet.
They can weight up to 4 metric tons.
The Color Changing Cuttlefish
Cuttlefish, and other cephalopods change colors by using chromatophores. All
of this is under the control of the cuttlefish’s advanced nervous system. When
the muscles are relaxed, the surface area of the sac is small and the color is
not expressed. When the muscles contract the surface area becomes much
greater and the color is seen.
Cuttlefish use the change in color for mating purposes and to communicate.
Cephalopod Behaviors
Navigation and Spatial Maps:
 species Octopus vulgais found in Bermuda is a
cental place forager- uses a spatial map.
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finds and lives in homes of shells, beer bottles,
or sheltered niches. environment.
This same species of octopus also seems to
cover different parts of its home range one after
another on subsequent hunts and days which
suggests they also have a working memory.
Cephalopod Behaviors
“Playing” behavior:
A group of Octopus at the Seattle Aquarium were
subjected to 10 trials over 5 days. On the first trial each
was given a floating bottle. During this trial all the
individuals grabbed the bottle and brought it to their
mouths. Several of the octopuses jetted water at the
bottle during later trials. But two of the octopuses aimed
water jets that made it circle the tank and come back to
them for further jets. One octopus set it up so that the
bottle circled the tank for a round trip time of 2 minutes.
The other made it return every 30 seconds.
Conservation
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Currently cephalopods have no conservation
status
Very little known about cephalopod natural
history.
The California Department of Fish and Game
recommended a management plan for the squid
fishing industry. This plan was signed into law on
September 20, 2001.
The Australian Giant Cuttlefish’s population was
decimated in 1997 and 1998. In 1998 the
commercial season was closed early and a
complete closure occurred in 1999 and 2000.
concerned local sport divers have rallied to
establish permanent refuges and long-term
conservation plans.