Viewed from afar, the guitarfish is a strange sight: with its long body and triangular head, the enormous ray looks a bit like a shark who swallowed a guitar. Up close, the guitarfish, a member of the Rhinobatidae family, looks even stranger. Thatâs because the giant fish doesnât have eyelids. Instead, to protect itself from sand and debris, it retracts its eyes back into its head almost 1.6 inches.Â
In a recent study , published in Zoology , scientists announced their discovery of the muscle responsible for the guitarfishâs retractable eyes. Called the obliquus inferior, the muscle is attached to the underside of the fishâs skull, and allows the fish to pull its eyes backward into its head.Â
Scientists used a range of methods, from dissections to video recordings, to identify the specific muscle responsible for the fishâs strange eye movements. While digital recordings allowed them to measure the depth of the retractions, the biggest breakthrough came when scientists began electrically stimulating the eye muscles of dissected fish. They found that stimulation of the obliquus inferior caused the fishâs eyes to sink ventrally.
Guitarfish arenât the only animals with retractable eyes: frogs, bottlenose dolphins, skates, and several other species also share that strange skill. However, the distance that guitarfish are able to retract their eyes is likely unique. âThe eye retraction distance was nearly the same as the diameter of the eyeball itself, indicating that eye retraction in the giant guitarfish is probably one of the largest among vertebrates,â the study explains. Check out its strange ocular gymnastics, courtesy of Science Magazine , below.
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