molluscs gastropods cephalopods bivalves. classshellexamples gastropods shell – less or single...
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Molluscs
GastropodsCephalopods
Bivalves
Class Shell Examples
Gastropods Shell – less or single shelled
Land snails, slugs
Bivalves Two shells held together by powerful muscles
Clams, Oysters, Mussels
Cephalopods Only small internal shells or no shells
Octopus, Squid, Cuttlefish, Nautilus
AnatomyThe basic body plan of mollusks consists of: A muscular foot, the mantle (contains glands that secrete the shell) and the visceral mass (heart, digestive organs)
OCTOPUS (cephalopod)
The most highly evolved of the invertebrates.
Muscular foot has evolved into tentacles.
Octopus have no bone structure but do have a skull, a shell rudiment and a beak.
An octopus has eight arms, each with two rows of suction cups. If it loses an arm, it will eventually regrow another one.
Defense Mechanisms1.Their main defense system is AVOIDANCE
a) MIMICRY: They use camouflage to escape predators and catch prey .
b) They release ink and initiate flight.
How do they camouflage?By changing shape: It can flatten out or contract inward in a variety of shapes.
It can imitate a fish, like the flounder, or a sea snake.
By changing color: Sacs of yellow, red, brown and black pigment called chromatophores cover their bodies and allow them to change colors and patterns by contracting their muscles. Tightening certain muscles can also transform the texture of their skin to look like the smooth ocean floor or a craggy reef.
The octopuses of the genus Grimpoteuthis are also known as "Dumbo Octopuses" from the ear-like fins protruding from the top of their head-like bodies, resemblingthe ears of Walt Disney's flying elephant. They live at extreme depths: 3000-4000 m.
The beautiful and deadly Blue-ringed Octopus can be found in the Pacific Ocean between Australia and Japan. When it is full grown, it is only the size of a golf ball.
The Giant Pacific Octopus, the largest and longest living species of octopus , can be found in the Pacific Ocean, from CaliforniaTo Alaska.
The biggest one found to date weighed 272 Kg and had an arm span of 9 m.
The indonesian mimic octopus