Page 19 - World of Animals - Book of Sharks & Ocean Predators

50 facts about sharks
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7 If a shark stops swimming Shark bites

does it drown?
4. Spiracle
Bottom-dwelling sharks have an opening Do sharks have
It’s essential that sharks keep moving in order to get enough water across behind the eye that can pump water over the 9 bones like dolphins?

their gills to breathe, find out more about shark respiration below…
2. Gill slits gills when the shark isn’t moving. No. Sharks belong to the
It passes over the gill bars elasmobranch group of fi sh
and exits through the that have lighter, more fl exible
gill slits.
Gill arch cartilage in their skeleton,
Gill septum
1. Inhale instead of bone. Their muscles
Capillaries Water enters through the are anchored directly to the
mouth, driven by the forward inside of their tough skin.
Oxygen-depleted water motion of the shark.
Gill fi laments
How do sharks
10 stay buoyant?
Sharks don’t have a swim
bladder like other fish, so they

use their liver instead. The
amount of squalene oil stored
there is adjusted to leave the
shark slightly heavier than
water. The extra buoyancy is
supplied by dynamic lift from
5. Gulping

Some species also use the the shark’s fins as it swims
mouth to actively gulp water
across the gills.
How good is a
11 shark’s eyesight?
Oxygen-rich water Sharks have good night vision
and can contract and dilate
their pupils, which bony fi sh
Gill arches can’t. Sharks are either colour-
blind or can see only shades
Ventral aorta of grey and green, depending
on the type of shark.

“A greatwhite shark Does a shark’s
Heart
12 skin help it to
can get through swim faster?
Shark skin is covered with
up to 50,000

scales like other fish, but shark
3. Passive ventilation
8 Open-water species need to keep teeth in its life” scales are made from dentine
swimming anyway or they will sink, so
and actually resemble tiny
this system works fine.

teeth more than scales. These
How many teeth does ‘dermal denticles’ generate
tiny vortices on their trailing
edges as the shark swims and
a shark get through in this vastly reduces the shark’s
drag through the water.
a lifetime? Why is this
number so high?
Shark teeth aren’t
embedded in the
jaw, but attached
to the skin. They The huge jaws of a
are designed to prehistoric shark,
be disposable and the megalodon
are continually
replaced like a © DK Images
conveyor belt from
the back of the
mouth. A great
white shark can
Growth
get through up to
Layers of razor-sharp, serrated © Getty
50,000 teeth in teeth roll forward to replace broken
its lifetime. or missing ones.
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