Sharks

 

What is a shark?

Sharks belong to a group of cartilaginous fish called elasmobranches that also include the rays. These ancient creatures have been on the Earth for more than 100 million years and lived during the time of the dinosaurs. An English fisherman discovered and named the shark in 1565. Sharks range in size from a whale shark that can grow over 45 feet long to the diminutive pygmy shark that is less than 8 inches long.

Sharks are fish

Sharks possess the following characteristics:

  1. Cartilaginous skeleton: Sharks have no bones. Touch the tip of your nose and you will feel cartilage. The cartilage of the shark’s skeleton is hardened by calcium, especially the vertebral column. Red blood cells are produced in the kidneys and n an organ called the epigonal.
  2. Spiracles: Sharks use these round openings behind the eyes to assist with respiration. Water enters the spiracles or mouth and exits through the gill slits.
  3. Five to seven pairs of gill slits: Look closely on the side of a shark’s head and you will see five to seven pairs of gills slits that are used for respiration.
  4. Dermal denticles: Derm means skin and dent means teeth. These scales, or “skin teeth,” are composed of the same material as teeth and help streamline and protect the shark.