FREE ESSAY ON THE LEOPARD SHARK

THE LEOPARD SHARK

Leopard Shark (Triakis semifascicata)
Family Carcharhinidae (requiem sharks).
Order Chiamydoselachiformes
The Leopard Shark (Triakis semifascicata) is in the Family of Carcharhinidaes (requiem
sharks). Carcharhinidaes are the largest family of sharks in numbers. This family
consists of bull sharks, sandbar sharks, tiger sharks, great blue sharks and more. The
Leopard shark (Triakis semifascicata) grow to 7 feet and are heavily marked with black
crossbars and blotches. Their teeth are short, broad and triangular shaped. The Leopard
sharks (Triakis semifascicata) are active, fast sharks. They are nomadic, schooling
sharks that roam inshore sand flats and rocky areas. They are known to feed on soles,
bivalves, crustaceans, and other small bottom dwelling fish.
Sharks have been around for 400 million years and out of that 400 million years about 100
million years the sharks and their close relatives have been closely unchanged in
appearance. There are about 900 species of sharks and their close relatives. There are
about 400 species of sharks and more are been found and added to the list.
What makes a shark a shark? First it's skeleton is made of cartilage, which is lighter,
tougher, and more flexible than bone. The most noticeable difference is its teeth.
They're jaw is lined with teeth, acting as a conveyor belt with new teeth replacing the
old, broken and lost teeth. 
As a matter of fact their entire body is covered in tiny tooth-like scales called dermal
denticles, which, unlike those of bony fish, do not enlarge while the animal is growing
larger. Another difference is that fertilization takes place inside the female with 1 of
the2 claspers inserted into her. The males use the claspers to inject the semen into her.
The claspers are extensions of the pectoral fins. Unlike bony fishes, which usually spawn
in great masses of tiny, immature young, most sharks produce large, well-developed
offspring numbering, at the most, 100 to a litter. Most sharks are ovoviviparous,
hatching the eggs within the female and bearing live young. Some sharks are oviparous,
however, laying their eggs externally. The eggs are often encased in leathery shells with
tendrils that anchor them to rocks or seaweed. Others species of sharks are viviparous.
Which means the yolk sac becomes a yolk placenta in the folds of the uterine wall and
gives nutrients to the embryo. Embryonic development takes more than six months. The
young are frequently born in protected closer to shore areas away from the males. Sharks
commonly fast for long periods during the breeding season and live on the vast reserves
of lipids stored in their livers. This helps the sharks survive because it decreases
cannibalism from the mother. The shark's tail is asymmetrical, with the vertebral column
extended into the upper lobe. The fins and tails of sharks are rigid. Going against the
popular image, the dorsal fins rarely project above water when the fish are close to the
surface. They have strong digestive enzymes and a specialized epithelial fold that
spirals the length of the small intestine, enabling the fishes to absorb a great
diversity of foods. Sharks, to a large extent, are scavengers, eating injured fish,
garbage, and other waste from ships as well as animals such as seals, turtles, birds,
whales, crabs, and a wide range of fishes. The most interesting difference is called the
Ampoules of Lorenzini, which detect faint electrical currents from other fish. All living
things generate electrical fields due to the contracting of muscles and sharks have
adapted to being able to use this as an advantage to find prey. Sharks have a very
excellent sense of smell. They are able to detect small substances, such as blood in
water and trace them to their source. Their sense of sigh allows the shark to catch dim
movements of shadow and light in dark waters as it approaches its prey. Sharks are
particularly sensitive to sounds of low frequency and have fine directional hearing.
Organs along their lateral lines and on the snout enable sharks to pick up weak
electrical stimuli from the muscle contractions of bony fish. Their combination of keen
senses accounts for the evolutionary success of sharks. The sharks also do not obtain a
swim bladder, so they seem to be in constant motion. If the sharks stop swimming they
will slowly sink to the bottom. They also have 5, 6, or even 7-gill slits instead of1
that bony fish have.
The world has been tough on sharks. During a 17- month period in the 1930's, 1,500 sharks
were caught by the mesh net method along the Australian beaches to keep swimmers safe. Up
to 1,400 plus many dolphins are caught each year in South Africa. There is no easy way to
keep sharks away from places where people swim, surf or scuba dive. Shark proof
enclosures have been built, but these can only protect small areas because of the large
coastlines. In South Africa and Australia, nets are used to trap sharks on popular
beaches. But the "man- eating sharks" aren't the only victim of the nets. These nets also
trap and kill many harmless sharks, dolphins, sea turtles and rays. Tests are being done
to see if electrical barriers can be used, that wouldn't harm or kill the sharks and
other animals in the process. An American scientist Dr. Eugenie Clark discovered that the
Moses Sole from the Red Sea makes its own shark repellent. When the Moses Sole is
attacked, it secretes a milky, toxin ooze out of it's skin and the shark will spit it
out. This is another way to prevent shark attacks.
Sharks play an important ecological role in oceans, similar to that of large predators on
land. Sharks prey on weakfish, thereby helping a species to maintain its genetic
strength. Because modern fishing methods have helped to deplete many food-fish species,
however, the industry now views sharks as competitors, to the extents that shrimp
trawlers frequently employ electrical shields by their trawls to keep sharks from
destroying the catch. On the other hand, with the increasing scarcity and rising price of
many food fishes, especially for United States consumers, shark meat is itself now
selling at prices comparable to those for traditional table fishes. The meat has long
been eaten, especially in East Asian countries, but it is now increasingly being featured
in United States markets and is often compared to swordfish. Also the shark's fins are
made into soup.
Sharks have a bad reputation as bloodthirsty killers. But only a handful of sharks are
dangerous and attacks on people are rare. Shark experts are concerned that sharks are
increasingly threatened by over fishing. In Florida, Lemon sharks are threatened due to
the destruction of Mangrove Swamps, which are important nurseries for Lemon shark pups.
Many people begin to like and admire sharks as they learn about them.
Bibliography
Bibliography
1. http://www.marinelab.sarasota.fl.us/SHARKS.HTM
2. OCEAN LIFE by Marty Syderman, The International Oceanographic Foundation
Copyright date 1991
3. The Complete National Geographic 109 years of National Geographic Magazine on CD-ROM
4. Eyewitness Encyclopedia of Nature 2.0 Copyright date 1995
5. Edmark's Imagination Express DESTINATION: Ocean