Buzz
From a distance, the guitarfish presents an unusual image: with its long, slender body and triangular head, it resembles a shark that has swallowed a guitar. But up close, the guitarfish, belonging to the Rhinobatidae family, appears even more bizarre. This is because the massive fish lacks eyelids. Instead of eyelids, it can retract its eyes into its head by nearly 1.6 inches to shield them from sand and debris.
A recent study, published in Zoology, revealed the discovery of the muscle responsible for the guitarfish’s retractable eyes. Named the obliquus inferior, this muscle is anchored to the fish’s skull’s underside, enabling the fish to draw its eyes backward into its head.
To identify the muscle behind this unique eye movement, scientists used a combination of techniques, including dissections and video recordings. While digital footage allowed them to assess the depth of eye retraction, the significant breakthrough came when they electrically stimulated the eye muscles of dissected fish. This stimulation of the obliquus inferior muscle caused the eyes to move downward into the head.
Guitarfish aren’t the only creatures with retractable eyes: frogs, bottlenose dolphins, skates, and other species possess this peculiar ability as well. However, the distance that guitarfish can retract their eyes is probably unparalleled. “The 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,” the study notes. Take a look at its unusual ocular gymnastics, courtesy of Science Magazine, below.
