2-minute read
If you’ve been celebrating Shark Week by binging and cringing your way through Jaws 1-4, you’re probably thinking that the massive teeth of those fictional fish are pretty darn scary. Well, maybe not the teeth so much as their limb-chomping potential. Now imagine a real-life shark with close to 3,000 teeth in its five-foot-wide mouth and a couple of thousand more covering its eyeballs. Talk about the fear factor! Except the real-life shark with all of those teeth is the whale shark (Rhincodon typus), and despite being about the size of a big yellow school bus, the primarily plankton-eating fish is quite a gentle creature.
While sharks are a notoriously toothy bunch, scientists at the Okinawa Churashima Research Center studying optical adaptations in vertebrates recently discovered that the whale shark has tiny teeth where they didn’t expect to find them—around its iris. So why does the whale shark need eye armor? Unlike most vertebrates, the fish has no eyelids to protect its small, protruding peepers from underwater hazards. The oak leaf-shaped tooth-like projections, known as denticles, shield the shark’s eyes from abrasions as it travels the Pacific, Indian, and Atlantic oceans in search of the large quantities of food that it needs to survive.
As if that evolutionary adaptation weren’t freaky enough, the whale shark has another unusual eye protection mechanism to compensate for its lack of lids. If the situation calls for it, the whale shark can retract its eyeballs into its eye sockets. One eye retraction event observed by researchers was in response to camera strobes. It seems that despite being popular subjects for underwater photographers, whale sharks are no fans of the flash. Although a few other lidless species, including electric rays, guitarfish, and leopard frogs can also tuck in their eyeballs, the whale shark’s retractable, armored eye combo is fairly rare.
Sadly, like many shark species, the whale shark is threatened with extinction. The global numbers of the large, slow-moving fish have more than halved over the last 75 years as a result of overfishing, bycatch (see video), and propeller strikes. The whale shark is now listed by the International Union for the Conservation of Nature (IUCN) as endangered. As recently reported in Science, sharks are now functionally extinct in the waters of eight countries.
Even though these dentally well-endowed creatures may look like they can handle whatever comes their way, sharks still need all of the support that they can get when it comes to protecting their habitat. You can learn more about these fascinating fish and what you can do to help keep them safely in the swim from Ocean Conservancy. And you can track migrating whale sharks in real-time via satellite courtesy of Conservation International.
