As fearsome
as this guy looks, he actually wouldn't harm a hair on your head. Whale
sharks may have big mouths, but it isn't for swallowing people - they're
plankton
feeders. Plankton are microscopically tiny organisms that thrive in
the oceans throughout the world. That's what the shark in the above
picture is doing - feeding on plankton. You may not see them in the
picture, but he knows they're there.
The huge, gaping
mouth is the whale shark's adaptation to feeding on plankton; the wider
his mouth opens the more plankton he can scoop up with each "bite".
All the water that he takes in to scoop up his meal is simply passed
out of his body through his gills, which have sieve-like membranes covering
them to filter out the little critters and prevent them from escaping.
If you were accidentally scooped up by the whale shark you would find
yourself being spit back out through an interesting process called gastric
eversion. The whale shark actually
turns its stomach inside out and spits it out through its mouth, ejecting
the entire contents.
Is it A Shark or a Whale?
You may wonder
why this fish is called a whale shark. Scientists have determined that
it is a species of shark, because of its skeleton (composed entirely
of cartilage), and its tough, leathery, scaleless skin. People called
it a whale shark because of its enormous size (like a whale), not because
it's a type of whale. A whale is a mammal; a warm-blooded creature that
has lungs and breathes air, gives birth to its young and nurses them
with milk produced by mammary glands. A shark is a fish; it "breathes"
its oxygen by passing water over its gills.
Whale sharks
are rare, elusive creatures that scientists still know very little about.
One interesting adaptation of the whale shark that scientists have discovered
is that it has sensors that run the length of its body which are used
for detecting pressure changes in the surrounding water. Whale sharks
swim with their huge mouths wide open to chow down, making it hard for
their proportionately small eyes to see where they're going. Being able
to detect large objects with their pressure sensors gives the shark
a "sixth sense" that acts like back-up vision.
