Whale sharks, the majestic creatures that likewise happen to it is in the world"s biggest fish, space far an ext gentle than the name suggests. They swimming lazily approximately tropical waters, filter-feeding ~ above plankton.

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Now, biologist have found the enigmatic giants have a curious trick up your sleeve – teeth-like scales adorning your eyeballs. It shows up to be the whale sharks" variation of eyelids, and one us haven"t checked out in any kind of other vertebrate.

"Eyeballs face a potential danger of damage from mechanical, chemical and also biological hazards," the researchers write in a brand-new paper describing the find.

"This report elaborates ~ above adaptations of the eye of the whale shark (Rhincodon typus), including the discovery that they are covered v dermal denticles, which is a novel device of eye defense in vertebrates."

Dermal denticles, also known as placoid scales, are the tiny tough scales the cover sharks and also rays. However although lock are scales as we think the them, they"re additionally structurally very comparable to teeth, and include an inner main point of pulp, a center layer that dentine or bony tissue, and also a tough enamel-like coating on top.

We currently knew that plenty of sharks - consisting of whale sharks - room covered through these denticles. However, finding them on the eyeballs of these fish is quite the surprise.

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Eye denticles the the whale shark. (Tomita et al., PLOS One, 2020)

That"s partially since it"s long been presume whale sharks don"t have to use their feeling of sight much: their eyes room incredibly tiny compared come the rest of your body, and they don"t have actually a lot of midbrain, the part of the brain that procedures vision.

"However, the highly protected features of the whale shark eye, in contrast to the classic view, appears to imply the prominence of vision in this species," the team argues in your study.

Researchers take it a CT scanner come a maintained whale shark eyeball, as well as taking ultrasounds of 2 captive live whale sharks in ~ the Okinawa Churaumi Aquarium in Japan.

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3D calculation of the morphology of every eye denticle. (Tomita et al., PLOS One, 2020)

As well as learning the eye denticles, the researchers likewise elaborated on the mechanisms whale sharks use to retract your eyes ago into your head. Many of the time this deserve to be for simply a short duration of time, yet not always. Once, a particularly unfortunate shark finished up with its eye retracted for 10 job after the was transferred to a new aquarium native Taiwan to Atlanta, Georgia.

"It is most likely that whale sharks preserve their vision throughout eye retraction because the pupils of the whale sharks in this study were not completely covered with bordering white tissues when their eyes had actually retracted, though their visual ar would be lot more minimal than as soon as their eyes are positioned normally," describe the researchers.

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"In fact, the animal that retained its eyes retracted for around 10 days at the Georgia Aquarium showed up to have no trouble navigating the exhibition space, till its eyes went back to their regular positions suddenly and, apparently, spontaneously."

So, if whale sharks aren"t precisely a fearsome predator the the ocean, these 2 eye-protecting attributes are a fearsome contender to... Eyelids.