Laurene Primer, age 12, of Pittsburgh, Pa., for her question:
WHAT IS A NAUTILUS?
Out in the deep, dark ocean lives a little animal about the size of your fist. Although we don't get much of a chance to see him, we know that he is there. In 1870 Jules Verne wrote a book about Captain Nemo and his fantastic submarine the Nautilus. In 1880 Robert Fulton named his newly completed submarine the Nautilus. And guess what the name of the first U.S. atomic submarine was? Right the Nautilus.
The sea is home for thousands of fish type animals. There are also an almost endless number of not so fishy animals, and one of these is the nautilus. He is a member of the mollusk clan and is related to the snails, mussels and clams. But his closest relatives are the squids, octopuses and cuttlefish.
During the Paleozoic Era, which began some 600 million years ago and lasted for 327 million years, he was one of the dominant forms of life found in the seas. Although today he only measures about 10 inches in diameter, at that time he was a whopping 16 feet long. Scientists have identified at least 2,000 species from their fossilized remains, but, sad to say, only about a dozen species live today.
The nautilus looks somewhat like a small squid living in a borrowed snail shell. His large shell is his own, of course, and looks like a coiled watch spring. Many shells are cream or soft brown in color, but some have striking stripes of deeper red brown. Inside the shell is a beautiful rainbow ¬colored substance called mother of pearl, or nacre. Because of this substance he is often called the pearly nautilus.
The body of a full grown nautilus is about the size of a man's fist. His head peeks out and is surrounded by 60 to 90 or more slender tentacles. The tentacles are used for gathering food. When he snares a tasty tidbit, he uses his tentacles to push it back into his mouth. Two beady eyes peering out from under a hoodlike structure give him a somewhat sinister look.
A nautilus shell is composed of many small chambers, each chamber a bit larger than the one before it. As the nautilus grows and gets too big for his present home, he builds a new one and seals up the old one.. He leaves behind in each chamber, however, a slender fleshy tube called a siphuncle. The siphuncle connects all the chambers and is used to secrete, or absorb, a gas the nautilus can make. This helps the nautilus go up or down in the water much like a modern day submarine.
The chambered shell of the nautilus may be made up of 30 or more chambers. By adjusting the amount of gas in each chamber, he can rise to the surface of the sea or sink down as deep as 1,800 feet. Nautiluses live in the South Pacific and Indian oceans.