Tamra Gaskins, age 10, of Lake City, South Carolina, for her question:
When do fish sleep?
People used to think that fishes never go to sleep. Certainly they never close their staring eyes. But this is because they can't. Actually fishes have see through eyelids. They are sealed shut like glassy windows. So they cannot close their eyes as we do. This makes it hard to figure out whether a fish is awake or asleep. Scientists would like to know a lot more about this interesting question. But they now feel sure that most fishes take rest periods and at least some of them go to sleep.
There are hundreds of different fishes and each one has his own way of life. The prettiest ones live around tropical islands and coral reefs. The masses of rainbow¬tinted corals look like lovely underwater gardens. The pretty little fishes dart among the tufts of stony coral and waving seaweeds. Some of them are called sleepers because they speed most of their time dozing on the sandy floor. If nobody disturbs them, these lazy sleepers seem to sleep day and night, though of course they must wake up now and then to grab themselves a bit to eat.
The wrasses and the gaudy parrot fishes also share the blue green watery world of the coral reefs. We know that these colorful fishes go to sleep, though usually they sleep only at night. When the watery world grows dark, the wrasse fish sinks to the bottom. He lies on his side and wriggles around until most of his body is covered with a blanket of sand. The sandy blanket does not keep him warm. But it does hide him from his hungry enemies.
The gaudy parrot fish has a built in system to protect himself when he takes. a nap. He oozes a sticky slime with a horrible flavor. This is spread over his body and when a hungry enemy takes a sniff, he decides to go off and find a more tasty meal. When darkness falls, other fishes find quiet caves among the tufts of stony coral. There they go to sleep. Often a poke in the ribs or a bright flash light does not wake them up.
Most fishes cannot abide sudden changes from hot to cold or from cold to hot. Many of them do not mind so much when the changes come slowly with the gentle seasons, though others swim on long journeys to enjoy the summers or winters where the temperature is more to their liking. But some fishes cannot leave their fresh water streams and ponds. Many of these spend the winter in the long, deep sleep of hibernation. Others sink into a long, deep sleep when the summer gets too hot and suffocating.
Out in the open seas, most fishes lead a hungry life. Day and night the larger ones hunt the smaller ones. There is no time to rest, no time to sleep. As a rule, schools of smaller fishes must swim faster during the night to escape their hungry foes. The greedy sharks have huge appetites and they are always famished. The flying fishes are never safe, always ready to leap out of the water to escape the sharks. Some experts think that these dainty fish never dare to sleep, day or night.
If you have a pet goldfish, maybe you think he never sleeps. But his glassy eyelids may fool you. Watch when he stops swimming around, sinks down low in his bowl and hovers lazily in the water. Chances are, he is taking a nap. And he is more likely to do this at night, when you do.