Did you know? Certain shark species—including the blacktip reef shark and the great white shark—need to swim in order to breathe, and therefore survive. When swimming, these sharks open their mouths and water flows directly across their gills. This process is called ram ventilation.
As water passes over the shark’s gills, tiny blood vessels extract oxygen from the water. This process requires more work for some species than others. For sharks that require ram ventilation to breathe, they must keep moving to allow water to move through their mouths because they lack the ability to draw in water.
Sharks that use ram ventilation lack the ability to buccal pump, which is when a shark’s mouth muscles actively draw in water and pass it through the gills. This process allows them to breathe without swimming. Certain species of sharks, as well as all rays, even have respiratory openings behind their eyes, called spiracles—meaning they can breathe while buried in the sand or resting on the bottom!
One of the shark species at the National Aquarium that uses buccal pumping is the zebra shark. In Blacktip Reef, guests can sometimes spot two zebra sharks—Zeke and Zoe—resting on the exhibit floor. When resting on the bottom of the exhibit, Zeke and Zoe use their strong buccal muscles to draw in water and generate gill movement. These sharks also use their strong buccal muscles to easily inhale prey in one gulp, a process called inertial suction feeding!
Another one of shark species at the Aquarium, the sand tiger shark, has the ability to use both ram ventilation and buccal pumping to breathe. Ram ventilation is used at moderate to elevated speeds, while buccal pumping is utilized at hovering to low speeds, as well as when resting on the bottom. Sand tiger sharks, unlike other sharks, swallow and expel air to adjust their buoyancy, and that is why they can hover or swim very slowly without sinking.
Stay tuned for more shark updates!