Head Foot Octopuses are cephalopods. T is Greek word means “head-foot.” An octopus's arms are attached directly to its head. Cephalopods were among the fi rst animals to hunt in seas more than 500 million years ago. Today, there are more than


750 known cephalopods. A giant Pacifi c octopus can weigh more than 90 kilograms (198 pounds). A star-sucker pygmy octopus weighs less than 20 grams (one ounce).


Octopus 101


An octopus makes decisions not just by using its brain but also by using its arms.


BRAIN The brain makes decisions and remembers things.


Counting Neurons T ese are intelligent animals. T ey have the skills to solve problems. How? T e answer lies in their nervous system. An octopus’s nervous system has cells called neurons. T ese cells carry messages to the brain. Diff erent neurons carry diff erent messages. With 500 million neurons, the octopus can do a lot of thinking. But the octopus is no match for humans. A human brain has almost 90 billion neurons.


s c n do a lot of thin in


stomach liver


central heart


ink sac


gills funnel ARMS


Each arm has a bundle of nerves and as many as 300 suckers. The nerves control the arms and send messages to the brain.


beak nerves


Pond snail Mouse 0.01


80


millions of neurons Octopus Human


500 86,000


6 NATIONAL GEOGRAPHIC EXPLORER


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