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Class: Chondrichthyes
The shark’s skeleton is entirely
composed of cartilage.
The skin is covered with tiny scales called denticles. Feels like
sandpaper.
They are similar in structure to teeth and cause the skin to be very
abrasive if rubbed in the wrong direction.
Most have gray, brown, white or black coloring; are not camouflaged
but may be counter-shaded.
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Predation: Efficient, top carnivore of the sick, weak, old and injured.
Sharks will not eat a fish called Moses Sole. Researchers think this
information may lead to a better shark repellant.
Jaw is lined with rows of teeth like
a conveyor belt. Teeth can be
replaced every 24 hours and are
used to identify species.
Jaw can be extended out of the mouth for extra reach.
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Their large liver may help detoxify their diet. It is unusual that
they are somewhat resistant to tumors and cancer.
However, shark cartilage does not
prevent cancer in humans, and sharks
with tumors have been observed.
Mote Marine Laboratory in Sarasota, FL
is a leading research center in shark
immunology.
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Circulation: 2 chambered heart; cold-blooded
Respiration: Gills are located in muscular slits behind the mouth.
They exchange oxygen from the water into the blood.
Sharks lack swim bladders and must constantly swim upwards
to balance their weight. They do sleep.
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Senses: Vision is good in clear
water. Eyelids close from the
bottom upwards to prevent
injury during an attack.
Their ability to smell is excellent. Olfactory lobes compose 2/3 of the
brain. Sharks can detect a drop of blood 1/4 mile away in the water
and can determine the direction of the source.
Hearing is also excellent. Sound vibrations can be detected by the
lateral line from 3,000 feet away.
The electrical impulses of breathing from a prey can be picked
up through pores in the face.
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Reproduction: sexual, internal fertilization. Most sharks have live
births. Dogfish have 4-10 pups, while tiger sharks may have 80-100
at one time. A few species of sharks and skates lay eggs. Shark
Egg
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Shark attacks on humans are rare, but
with more people in the water the odds
are increased.
Sharks may be looking for new
food sources due to over fishing.
Most attacks occur in less than 6 feet of water, at dawn or dusk,
during summer months. Risks are also increased for surfers and
swimmers in water with reduced visibility.
A surfer in black wet-suit, paddling out on a board, may look
enough like a seal to interest a shark.
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Most attacks occur in Florida,
California, Australia, and Africa. Florida
has 4 times the number reported in
California. Most attacks are not fatal.
Sharks only kill about 10 people worldwide per year. Bees kill
hundreds of people and crocodile/alligator - related deaths
number nearly 1000.
People have done far greater
damage to the shark population,
especially the illegal practice of
cutting the fins off live sharks to
sell for making soup.
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The whale shark is over
50 feet long. It is a filterfeeder with baleen instead
of teeth.
Largest shark
Most dangerous
Great White sharks are
found in the temperate
and tropical oceans
worldwide.
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Skates and rays are related elasmobranchs and cartilaginous fish.
Some are bottom dwellers that eat small invertebrates and some
small fish. Others are nekton, like the Manta Ray, and eat plankton.
Rays have live births (viviparous) while skates are egg laying
(oviparous). Several species of rays have a poisonous spines –
skates do not.
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Largest ray
Manta Rays may
have a 25 foot
wide wing span.
Most dangerous
Sting Rays have a venomous
stinger in their tail. Shuffle your
feet when wading to avoid
stepping on it.
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Remora Fish
• Grow to 30–90
centimeters long (1–3 ft)
• First dorsal fin takes the
form of a modified oval
sucker-like organ with
slat-like structures that
open and close to create
suction and take a firm
hold against the skin of
larger marine animals.
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Question: How Do Sharks Sleep?
Sharks need to keep water moving over their gills so that
they receive oxygen. So that means they need to keep
moving all the time... or do they?
Answer: Even though sharks need to keep water moving
over their gills to receive oxygen, some sharks need to
keep moving to do this, while others don't. Either way,
sharks, like other marine animals, don't seem to fall in a
deep sleep like we do.
Some sharks have spiracles, a small opening behind their
eyes, that force water across the shark’s gills so the shark
can be still when it rests.
Other sharks do need to swim constantly to keep water
moving over their gills and their bodies. These sharks
have active periods, and restful periods, rather than
undergoing deep sleep like we do. They seem to be “sleep
swimming,” with parts of their brain less active, or
"resting," while the shark remains swimming.
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