While longevity data are not available for many sharks, maximum
ages do vary by species. Some sharks like the smooth dogfish
may only live 16 years, while others such as the porbeagle
shark, may live as long as 46 years. Whale sharks, now the
largest fish in the world though they seem to be shrinking
in size, may well live over 100 years.
Sharks can shed and renew thousands of teeth during their
life, this is why sharks teeth can be found washed onto beaches.
A young shark may lose a set of teeth in a week. 'Spare' teeth
are ready to rotate forwards to replace broken or worn teeth.
They may have up to 3,000 teeth at one time. Most sharks have
about 5 rows of teeth at any time.
They have lots of teeth arranged in layers so if any break
off, new sharp teeth can immediately take their place. Shark
teeth also fossilize easily while the rest of the shark decomposes.
Shark teeth have the same basic consistency as ours, but
they don't sit in the mouth in the same way. Our teeth rest
in sockets and aren't replaced after childhood. Shark teeth
are attached to the jaw by soft tissue and fall out all the
time. This is crucial to the shark's effectiveness -- worn
or broken teeth are continually replaced by new, sharper teeth.
Sharks also have a very unique jaw structure which makes
their mouths especially effective weapons. In most animals,
the lower jaw moves freely but the upper jaw is firmly attached
to the skull. In sharks, the upper jaw rests below the skull,
but can be detached when the shark attacks its prey. This
lets the shark thrust its entire mouth forward to grab onto
its prey. Jaw mobility varies among different species but
all modern sharks have this ability to some degree. Most sharks
do not chew their food but gulp it down whole it in large
pieces. The front set is the largest and does most of the
Sharks teeth come in many different shapes and sizes, as
they are used to catch and kill different prey.
Some sharks have teeth that are very sharp, wide, wedge-shaped,
and serrated (having a jagged edge), designed for catching
and tearing apart prey (for example, the great white shark,
the tiger shark, the hammerhead and the bull shark). There
is a formula for calculating the size of a shark based on
the size of triangular tooth: measure the length of one side
of the tooth in inches, then multiply by ten to get the total
length of the shark in feet.
Some sharks have thin, sharp, knife-like teeth designed to
catch and hold slippery fish (for example, the lemon shark
and mako shark).
Many bottom-dwelling sharks have thick conical or flattened
teeth in the back of their mouths that are used for crushing
crabs and mollusks (for example, the nurse shark, Port Jackson
shark, angelshark, and zebra horn shark).