A new study from Japan’s Okinawa Churashima Research Center has found that the tough, dermal denticles that surround the eyes of whale sharks helps protect the eyes much like eyelids.
Whale sharks, which can grow over 30 feet in length, do not have eyelids like mammals or nictitating membranes like some some sharks that can protect the sensitive surface of the eyes.
As part of an effort to learn more about whale sharks, the researchers studied the eyes of both living and dead animals from aquariums and those washed up on shore. Whale sharks have protruding eyes contained in a casing that bulges out into the water, and on its tip is the visible part of the eye. The researchers found that the entire casing, except for the visible eye parts, is covered in dermal denticles with an oak-like shape that is similar to human molars.
Prior research had shown that whale sharks have dermal denticles on other parts of their body—in fact, on most of their body. The sharks have placoid scales, which are made of hard enamel and resemble teeth, unlike the scales of other animals. Such tiny teeth are not used for chewing, of course, they are used for protection. Their hardness makes it very difficult for other sharks to bite them. Also, the scales are arranged in a way that helps the shark swim faster.
These results were published on the open access site PLOS ONE.