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NURSE
SHARK
Ginglymostoma cirratum |
GENERAL
DESCRIPTION
The nurse shark is a large,
sluggish, bottom-dwelling shark that is generally harmless unless
provoked. It
has very strong jaws, a stout body, and a wide head with obvious
barbels (thin,
fleshy, whisker-like organs on the lower jaw in front of the nostrils
that
sense touch and taste). The fourth and fifth gill slits are very close
together. The dorsal fins (on the shark's back) are almost the same
size and
are rounded. Behind each eye there is a spiracle, an organ that takes
in water
used for breathing when the shark rests at the bottom.
The skin is dark gray-brown on top and some nurse sharks, especially
the young,
have spots. The nurse shark is smooth to the touch, unlike most sharks.
They are nocturnal hunters that rest during the day in groups. Nurse
sharks do
well in captivity.
No one is sure how they got their name; it might be because they make a
sucking
sound that is a little like the sound of a nursing baby.
SIZE
Nurse sharks range in
size from about 2-13 feet (0.75-4 m) long. The largest are about 14
feet (4.25
m) long.
TEETH
The nurse shark
has thousands of replaceable
teeth, which are serrated, and fan shaped; they are capable of crushing
shellfish. The teeth are arranged in rows that rotate into position
when one is
needed (when older ones are broken or lost).
DIET AND FEEDING
HABITS
Nurse sharks eat bottom-dwelling
fish, shrimp, squid, octopus, crabs, sea snails, lobster, sea urchins,
and
coral. The barbels (thin, fleshy, whisker-like organs on the lower jaw
in front
of the nostrils that sense touch and taste) help the shark locate
potential
food. Most hunting is done at night.
NURSE SHARK
ATTACKS
The nurse shark is a large,
sluggish, docile shark that is generally harmless unless provoked.
SOCIAL GROUPS
Nurse sharks congregate in
schools. They are sluggish or rest during the day, sometimes piled
together on
the bottom.
HABITAT
Nurse sharks live in warm waters
and are shallow-water sharks (going from the surface to 230 feet = 70 m
deep).
They are bottom-dwellers, living near sandy beaches, mudflats, and
sandbars.
They are common in coral reefs.
DISTRIBUTION
Nurse sharks are found in the
western Atlantic Ocean and the eastern Pacific Ocean.
REPRODUCTION
Nurse reproduce via aplacental
viviparity.
In aplacental
viviparity, the eggs develop
inside the body after internal
fertilization and hatch within the body of the mother. Litters consist
of 20-30
pups that are tiny replicas of the adult.
Nurse sharks reach maturity at about 15 to 20 years old.
MIGRATION
Nurse sharks do not migrate as
the water becomes cooler; their activity level simply decreases.
NURSE
SHARK
CLASSIFICATION
Kingdom
Animalia (animals)
Phylum
Chordata
SubPhylum
Vertebrata
(vertebrates)
Class
Chondrichthyes
(cartilaginous fish)
Subclass
Elasmobranchii
(sharks and rays)
Order Orectolobiformes
Family
Orectolobidae
Genus
Ginglymostoma
Species
cirratum
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