Sharks

Shark Facts Shark Facts TOO MANY TEETH If great white sharks had tooth fairies, they’d be rich! A great white loses and replaces thousands of its teeth during its lifetime. Its upper jaw is lined with 26 front-row teeth; its lower jaw has 24. Behind these razor-sharp points are many rows of replacement teeth. The “spares” move to the front whenever the shark loses a tooth. At any one time about one-third of a shark’s teeth are in the replacement stage.

Shark Facts  HEADS UP  Great whites are the only sharks that can hold their heads up out of the water. This ability allows them to look for potential prey at the surface. Great white sharks usually attack from underneath, surprising their unwary prey

Great white sharks are superstars. Before the Star Wars series, the 1975 movie Jaws was Hollywood’s biggest moneymaker. Jaws, about a great white on the prowl, cost $8 million to film but made $260 million in the U.S. Not bad for a fish story! Great white sharks can sprint through the water at speeds of 43 miles an hour. That’s about 8.5 times as fast as the top Olympic swimmer. Scientists on the California coast tracked one shark as it swam all the way to Hawaii—2,400 miles—in only a month! SHARK FACTS

 The largest shark known was the Megalodon now believed to be extinct. It was an ancient, meat-eating shark that lived between 25 million and 1.6 million years ago. It was up to 40 feet long and its teeth were each the size of a person's hand.ancient, meat-eating shark 

 Is it still alive??    MEGALADON

   nightmarish-megalodon.htm nightmarish-megalodon.htm  week/videos/megalodon-attacks-a-boat.htm week/videos/megalodon-attacks-a-boat.htm Shark Videos

 Along the sides of the body is a light-colored horizontal stripe called the lateral line. The line is made up of a series of tiny pores that lead to receptors that are sensitive to the mechanical movement of water and sudden changes of pressure.  The shark has a double dorsal fin. The anterior dorsal fin is larger than the posterior dorsal fin.  In addition, they have two pectoral fins, two pelvic fins, and a caudal fin. Anatomy

 The eyes are prominent in sharks and are very similar to the eyes of man. Just inside the lower lid is a membrane that extends over the surface of the eye to cover the cornea.  Large spiracle openings are located posterior and dorsal to the eyes. The spiracle is an incurrent water passageway leading into the mouth for respiration.  Most sharks have five external gill slits located on their sides behind the mouth and in front of the pectoral fins. Water taken in by the mouth and spiracles is passed over the internal gills and forced out by way of the gill slits. Anatomy

 The nares or external nostrils are located on the underside (ventral surface) of the rostrum anterior to the jaws. Water passes into and out of the olfactory sac, permitting the shark to detect the odors of the water.  The patches of pores on the head are the openings of the ampullae of Lorenzini. These sense organs are sensitive to changes in temperature, water pressure, electrical fields, and salinity. ANATOMY

 The valvular intestine is the second, and much larger, portion of the small intestine. It follows the duodenum and its outer surface is marked by rings.  The rectal gland is a slender, blind-ended, finger-like structure that leads into the colon by means of a duct. It has been shown to excrete salt (NaCI) in concentrations higher than that of the shark's body fluids or sea water. It is thus an organ of osmoregulation, regulating the shark's salt balance.  The spiral valve is the screw-like, symmetrical shape within the valvular intestine. It adds surface area for digestion and absorption to an otherwise relatively short intestine. Anatomy

 Paired testes lie near the anterior end of the body cavity, dorsal to the liver, adjacent to the anterior ends of the kidneys. The sperm pass from the testes to the kidneys within narrow tubules called efferent ductules.  After passing through the anterior end of the kidney the sperm enter the ductus deferens and pass posteriorly toward the cloaca.  The claspers are modified extensions of the medial portions of the pelvic fins. They are inserted into the female's cloaca during copulation.  The finger-like claspers each have a dorsal groove, the clasper tube that carries the seminal fluid from the cloaca of the male to the cloaca of the female during mating. Anatomy