Page 21 - Shark

eyes on stalks
Hammerheads’ eyes are Compass Imaginary
on the end of their head magnet
projections, giving them
a good view as they
swing their heads back
and forth. The nostrils are
widely spaced on the front of
the head, helping them detect
where an odor is coming from.
The head projections contain sensors
that detect electrical signals from
potential prey nearby.

coMpass sense
Some sharks migrate hundreds of miles
and they seem to know where they North-
are going, in what to us is a south
duck-billed platypus featureless ocean. Scientists axis
One of the few animals, aside think sharks have compass
from sharks, which has a sixth sense to guide them. In a real Earth’s magnetic field
sense of being able to detect compass, a magnetic needle swings
electric signals of its prey, is around to align itself to the Earth’s
the duck-billed platypus from magnetic field. The Earth’s magnetic field
Australia. The platypus’s electro- (above) is created by its molten iron core, which acts like a giant magnet.
receptors are on the lefthand Sharks seem able to swim in one direction by sensing changes in their
side of its bill. Platypuses live own electric fields in relation to the Earth’s magnetic field. Corrections
in streams where they hunt for have to be made for speed and direction of ocean currents, which
insects and other small creatures may sweep the shark off course. Sharks may also be able to
on the bottom. navigate by detecting magnetic patterns on the seabed.

Nurse
shark

Barbel

Feelers and
taste buMps
The pair of feelers,
or barbels, on
the nurse shark’s
nose (right) means it can
feel prey such as shrimp
hiding in the sand. Many of the
sharks that live on the seabed have
barbels that they use to probe the sand
for food. Barbels may also play a role in
taste. Sharks have taste buds on bumps in
their mouths and gullets (left). They spit out
anything if they do not like the taste.

Nostril

nice nose
Water is taken
in through the
epaulette’s
big nostrils
and passed
to a nasal sac
spotty nose where odors are smelt.
The spots in front of the nostrils on this sand tiger’s snout are sensory pores, Sharks can detect
called ampullae of Lorenzini. Full of jelly, the deep pores connect at their base very weak odors—as
to nerves. The pores detect the weak electric signals produced by their prey’s little as one drop of
muscles and bodily processes. Sometimes sharks are confused by electric Snout of an fish extract diluted a thousand
signals given off by metal, so they will bite shark cages (pp. 52–53). epaulette shark million times.

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