Swimming abilities of sharks contribute to their success
Sharks have survived the many changes to Earth’s environment since they first appeared during the mid-Devonian period around 400 million years ago. Much of their success can be credited to a hydrodynamic body design, which has given them the ability to become one of the top apex predators in the world’s oceans.
Among the most advantageous traits of a shark’s body is its efficiency in swimming, allowing sharks to keep up with or exceed the swimming capabilities of other competitors for survival in the oceanic environment.
A shark’s skeletal structure is among the many features that have allowed it to become an effective swimmer. Their skeletons are composed entirely of cartilage, which is relatively strong and significantly lighter than bone. This gives the shark’s body the internal support and strength needed to move quickly through the water without having to expend excess energy supporting the weight of a bony skeleton. This structure supports another key body feature: its fins.
Unlike other fish fins, which are composed of spines with skin-like webbing between them, shark fins are solid structures made of multiple filaments of cartilage, called ceratotrichia, which increase the strength of the fins to withstand the great stresses of water pressure.
Shark fins are usually thicker and rounded at the front and thinner and bladelike at the rear, which increases the ease of water flow around them in a manner similar to air flow around the wings of an aircraft.
The pectoral fins, which are positioned close to the head, are used for steering while the iconic dorsal fin on the back maintains stability and balance. The tail fin is its primary propulsion source and is powered by the unique musculature of the shark.
Shark muscles, called myomeres, are developed to carry the ideal level of blood flow and oxygen circulation to key areas of the body. Sharks that don’t rely on high bursts of speed will usually have more red muscle with higher levels of blood flow and oxygen for prolonged, continuous swimming, whereas those that rely on speed and agility will have higher levels of white muscle, allowing for fast bursts of speed for a short period of time.
This musculature is supported by the shark’s skin, which is known for its hydrodynamic qualities due to a unique feature called dermal denticles. These denticles, which are actually teeth that grow from the skin, are formed in a way that reduces the drag of water friction on a shark’s body as it moves through the water and increases the amount of speed a shark can produce. A shark’s body shape is streamlined in such a manner that many have likened it to an aircraft, allowing for maximum speed through the viscosity of water with little effort. For this reason, many engineering companies study shark body designs to create more fuel-efficient aircraft. The sum of these physical characteristics results in an animal that has survived for most of this planet’s history, becoming an integral keystone species of our ocean’s ecosystems, while continuing to inspire many with awe when viewed in the wild or on exhibit in an aquarium.
* Mike Ogata is a marine naturalist at Maui Ocean Center. “Ka Mo’olelo Moana,” or “the Ocean Story,” is a monthly column submitted by Maui Ocean Center staff members. The center is open from 9 a.m. to 5 p.m. daily in Maalaea. For more information, call 270-7000.