Animal Planet :: Shark! Beyond the Jaws

Ask a Shark Expert

Read shark researcher Mark Marks' responses on the following shark topics:

Disappearing sharks
Shark evolution
Shark deterrent?
Nonstop swimmers?
Shark posturing
Swimming with the sharks?
Shark diving
Shark education
Shark enemies
Shark reproduction
Great white disposition
Favorite shark
Shark eyes
Shark companions
Bite pressure
Bladderless sharks
Warmblooded killers
Hammerheads
Thresher sharks
Great whites in captivity
Shark protection

Q: On Bladderless Sharks

Hi Mark, I was led to believe that ALL sharks are WITHOUT a bladder ... and just recently, a friend informed me that it is only the blue shark that does not have a bladder. If you would, please tell me which is true. I appreciate your time and knowledge.

A: All elasmobranch fishes (sharks, skates and rays) lack a gas-filled swim bladder such as that found in bony fish. This is why no shark is completely buoyant, and the blue shark is no exception to the rule. Sharks maintain their "osmotic balance" by storing dissolved salts in their tissues, placing them in a kind of equilibrium with the surrounding water.

Did you know that sharks are quite sociable? Listen to an audio interview with Mark Marks.