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Whales, Dolphins & Porpoises
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Weird & Wacky Ocean Animals
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Most sharks swallow their food whole or bite it into relatively large pieces.
Sharks have U-shaped stomachs that use very strong acids and enzymes to dissolve most of what is eaten.
The stomach produces an easily absorbed, soupy mush. Only this liquid mush enters the intestines because the pyloric valve, the valve between the stomach and the intestines, is small. Indigestible things, like very large bones and non-food items, are vomited.
Absorption of nutrients takes place in the intestines. Although the intestines are short, they have a large surface area due to infolding of the inner surface of the intestines.
Some shark intestines are arranged in folds, some are in a spiral pattern, like a spiral staircase enclosed within a cylinder.
Sharks need up to four days to digest their food.
ANATOMY AND REPRODUCTION:
Female sharks are larger than males.
Males have claspers, which are elongated pelvic fin edges. Claspers are used to transfer sperm to the female and fertilize her eggs.
Females have a cloaca, one opening that serves digestive and reproductive functions.
Sharks are born 3 different ways depending on the shark species.
Viviparous: The eggs hatch inside the female's body and the babies are fed by a placenta which transfers nourishment from the mother to the babies. (Examples of Viviparous sharks: Bull sharks, Whitetip reef sharks, Lemon sharks, Blue sharks, Hammerheads, and Whale sharks)
Oviparous: These sharks deposit eggs, hiding the eggs among coral, which will hatch later if they are not eaten by predators. (Examples of Oviparous sharks: Zebra sharks, Swellsharks, and Hornsharks)
Aplacental Viviparity (Old Term: Ovoviviparous): The eggs hatch and the babies develop inside the female's body but there is no placenta to nourish the pups. The pups eat any unfertilized eggs and each other until they are born. (Examples of Ovoviviparous sharks: Great white sharks, Mako, Nurse sharks, and Tiger sharks)
Viviparous Birth Video Example...
Oviparous Birth Video Example...
PAST AND PRESENT USES OF SHARKS:
Before sandpaper was invented the rough skin of sharks was used to smooth and polish wood.
Japanese warriors once wrapped the skin of sharks around their sword handles to keep them from slipping from their hands.
Indians in Florida used great white shark teeth as arrowheads and natives of many island of the Pacific used shark teeth to make harpoons and weapons.
Once the denticles are removed from shark skin it is often used as leather for making shoes and other clothing items.
Shark meat is eaten in many Asian coutries.
Shark liver oil used to be the main source of vitamin A.
CAUSES OF DEATH:
Sharks and batoids have several predators, including other sharks, elephant seals, and humans.
Every year millions of sharks are killed by fisherman catching them and harvesting their fins for a delicacy in Asia called shark fin soup. The sharks are caught, their fins cut off and the body of the shark is thrown back into the water. Without it's fin the shark simple sinks to the bottom of the ocean and drowns. For more information on this subject, please take time to read the report Sharks In Trouble by the World Wildlife Fund (pdf format).
The shark is a very misunderstood creature. But it is an animal that we should research and discover more about before we run away from it with fear and dread.
There are dangerous species of sharks, but just because they are a danger doesn't mean we should destroy them. Sharks make up an important part of the eco-system in the ocean and should be respected as an important member of the ocean society!