Giant but Boneless: Whale Sharks Have No Hard Bones Like Humans
Fundacion Rapala – With a length that can reach up to 18 meters, the whale shark holds the title as the largest living fish in today’s oceans. However, did you know that despite its massive body, the whale shark does not have a single hard bone?
Interestingly, this unique fact doesn’t apply only to whale sharks—it’s true for all shark species. According to IFL Science, here’s why sharks are boneless.
Sharks Are Made of Cartilage, Not Bone
Instead of a bony skeleton, sharks are supported by cartilage. In humans, cartilage is the soft tissue found in our noses and ears.
For comparison, an adult human has about 260 bones, while infants have even more—nearly 360. Sharks, however, possess only 200 to 400 cartilage structures.
These cartilaginous structures are found in essential areas like the jaw, spinal cord, and skull. What gives shark cartilage its strength is the presence of calcium salts, which act like glue and reinforce the cartilage.
The only non-cartilage part of a shark’s body is its teeth, which are typically broad and flat like molars.
Why Cartilage Matters for Sharks
There’s a good reason why sharks evolved with cartilage instead of bones. First of all, cartilage is highly flexible, making it ideal for animals that spend their lives constantly swimming.
Secondly, cartilage helps sharks stay buoyant. Their large liver, filled with low-density oil, works in tandem with their cartilage to keep them afloat effortlessly.
Thirdly, cartilage enhances speed. According to Emma Bernard, Curator of Fossil Fish at the Natural History Museum in London, cartilage is lighter and more flexible than bone. This structural advantage allows sharks to swim faster than many bony fish.
Jaw Strength Despite No Bones
Even though their skeleton is soft, sharks possess incredibly strong jaws. Their upper jaw is not fused to the skull, allowing them to open their mouths wider and bite down with immense force.
Still, this design is not universal across all shark species. Bernard points out that shark skeletal structures have evolved across eras, suggesting ancient sharks may have had different skeletal adaptations suited to their lifestyles.
In fact, some prehistoric sharks may have had partially bony skeletons.
How Can They Grow So Big Without Bones?
One lingering question is how sharks like whale sharks can grow so enormous without hard bones. Surprisingly, the answer still lies in cartilage.
Because cartilage allows for faster and more agile movement, sharks can efficiently hunt and consume the food needed for growth.
A 2015 study explored the swimming patterns and body shape of whale sharks. It found that whale sharks use energy-efficient strategies to forage and conserve energy while diving deep into the ocean.
Whale sharks are negatively buoyant, meaning they’re denser than the surrounding water. This lets them sink naturally to deeper waters to feed without expending much energy.
The energy saved helps keep them warm and allows for longer feeding times, which in turn supports greater growth potential.
However, some experts believe that cartilage might ultimately limit how large a shark can grow. This may explain why whale sharks, despite their size, still don’t reach the colossal mass of blue whales—the heaviest animals on Earth.