The beautiful shell
Millions of years ago, the sea was full of many octopuslike animals. But
these animals had shells, like those of snails. Today, of course, the
octopus has no shell at all. And its cousin, the squid, has only a small
sliver of a shell inside its body. However, there is still one kind of
octopuslike animal that lives in a shell. It is the animal called a
chambered nautilus [(naw]{.smallcaps} tuh luhs).
A chambered nautilus is much like a squid or octopus. But instead of
eight or ten arms, the nautilus has as many as ninety. The body of a
full-grown nautilus is about the size of a man’s fist. And the nautilus
lives in a shell
beautiful, spiral shell that is creamy white, with broad, orange-brown
stripes. The shell is about ten inches (27 centimeters) wide.
Both the octopus and the squid protect themselves by squirting a cloud
of thick, dark ink to confuse their enemies. But a nautilus depends on
its shell for protection. Much of the time, its arms and the front part
of its body stick partway out of the shell. If any enemy appears, the
nautilus pulls itself into its shell. It closes the entrance with a
tough, leathery hood that is formed by four of its arms.
The spiral-shaped shell of a chambered nautilus has about thirty
compartments. This is why the animal is called a \”chambered” nautilus.
Because the chambers are lined with a shiny substance called
mother-of-pearl, this animal is also called a pearly nautilus. The name
Nautilus means \”sailor.”
The nautilus grows a new chamber each time it gets too big for the old
one. Then it moves into the new chamber and seals off the old one. The
old chambers are filled with a gas that enables the nautilus to sink
down or float up, as it chooses. However, it can also swim by squirting
water out of its body, as the squid and octopus do.
During the day, a nautilus hides on the sea bottom. At night, it hunts.
Its arms do not have suction rings as do the arms of squids and
octopuses. Instead, some of the arms have sticky patches. If the
nautilus catches a crab or shrimp, it is able to hold it fast.
As it grows, a chambered nautilus adds new chambers to its shell. All
the chambers form a beautiful spiral design when the shell is cut in
half.
