How Fish Sleep
By A. Hyatt Verrill
From Everyland magazine,
Everyland Nature Club column, Oct. 1916, digitized by Doug Frizzle, Dec. 2011.
DOESN'T it seem funny to
think of fish going fast asleep? Most people think of fish as always being wide
awake and swimming about, but, strange as it seems, fish sleep just like other animals, and some of them
even make beds in which to sleep.
Still other
kinds sleep upon the surface of the water and rest just as comfortably, when tossing
about on the-waves, as their cousins resting in their
beds on the bottom.
Some kinds of fish change their clothes
before going to bed and put on night-dresses which are so very different from their everyday clothes
that you would never recognize them,
while others never bother about such matters, but doze off wherever they happen to be when sleepy.
But the
funniest thing about fish sleeping is that they
never shut their eyes, for fish do
not have eyelids like most animals, and so they
couldn't close their eyes if they wanted to. For this reason fish are all very
light sleepers, and wake up at the
least change of light, or at a shadow moving past them.
This is why it is so hard to catch a fish asleep, for even in an aquarium the finny creatures wake up as soon as any one goes
near.
Some fish sleep much more
soundly than others, however, and
nearly all we know about sleeping fish has been learned by watching these heavy-sleeping species.
I said some fish made beds,
and any boy or girl who lives near a fresh water pond or stream in the United
States may find some of these with a little search. The common "pumpkin
seed," or "sunfish," is a fellow who makes these beds, which look like little hollows lined
with sticks and pebbles upon the
bottom of the pond or stream. If you
approach very cautiously you may be able to find one of the
fish resting in its "nest," and fast asleep, for fish doze in the daytime as well as at night. Another kind of fish, also known as the "sunfish," is a great giant of a
fish found in the open ocean, and
this sunfish is one of the kinds
which love to sleep on top of the
sea. This funny sunfish, which looks as if he were all head, is one of the largest of all fish, and when he sleeps he lies
in a nice comfortable position with his big fin sticking up in the air. This big sunfish is a very sound sleeper,
and sometimes one may be seen with half a dozen seabirds perched on his fin
while he slumbers on without knowing he is the
resting place of his feathered
friends.
But the
funniest fish are those which wear
nightclothes. One of these is the
common "blackfish," or "tautog," and as the blackfish are very sound sleepers, one may watch
them very easily when they are kept in an aquarium. During the day the
blackfish is dull colored, dark brown or nearly black, with faint blotches or
stripes, but when he goes to bed he changes his colors and sleeps in a suit of
silver and black. Like many other
fish, the blackfish rests on the bottom, and lies on one side, or propped up
against some rock or weed. If you should see a blackfish sleeping in this way
you would certainly laugh, for, resting on his side with his mouth half open,
he looks as if he were actually snoring.
Illustrations by the Author |
Another
common fish who puts on a night-dress is the
"scup" or "porgy." During the
day the scup is plain silvery gray,
but when he feels sleepy he puts on a coat of brown and gray stripes. Then he
searches about until he finds a nice comfortable spot among the eel grass or seaweeds where he goes to bed and
sleeps soundly, for he knows the
striped nightgown will make it very difficult for any enemy to see him among the shadows of the
weeds. It is for this very reason that the
sleeping fish change their colors,
for if dressed in their daytime clothes some prowling shark or other
foe might come along and gobble them
up before they were half awake. This
is known as "protective coloration," and while the
commonest fish—such as the blackfish
and scup, protect themselves in this
way, yet some of their cousins are much
more remarkable in their manner of
changing color to protect themselves
while asleep.
One of the
commonest and most wonderful of these
is the green parrot-fish, found
along the southern
coasts of the United States
and in tropical waters.
During the
day and when awake, the parrot-fish
is a beautiful clear turquoise green, but just as soon as he goes to the bottom to rest or to sleep, his colors change to
a dull olive covered with spots and blotches of brown. In this costume you
would never recognize him. But the
funniest part of it is that he knows when to change his coat and when
not to, and if he is placed in an aquarium with a plain green bottom he will go
to sleep in a coat of plain green. Then, if some stones or other objects are placed in the
aquarium he will make the brown
spots appear on his body, and unless you look very closely you will find it impossible to distinguish the wise little fish as he snuggles down among the pebbles in his piebald suit.
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