Neuroscience For Kids
Hammerhead Shark Eyes: Better to See You With!
December 2, 2009
Hammerhead sharks are one of the strangest animals in the ocean.
These creatures can have heads that are almost 50% as wide as their entire
body length. The shark's eyes are located on the sides of their wide
heads. Some researchers argued that the hammerhead shark would not have
good depth perception because there would be no
overlap between the visual fields of each eye; other researchers argued
that the wide separation between the eyes would improve depth perception.
But no one had tested the shark's eyes until researchers at Florida
Atlantic University and the University of Hawaii caught a few sharks.
In experiments published in The Journal of Experimental Biology,
the researchers measured the electro-retinogram (ERG) from the eyes of
several species of hammerhead shark. The ERG measures the response of the
photoreceptors in the eye. The visual field of
one hammerhead shark eye (monocular visual field) is about 180 degrees.
Surprisingly, the researchers found a significant overlap of the visual
fields from each eye. In fact, for the winghead shark, the binocular
overlap was 48 degrees! Because of this overlap, it is likely that
hammerhead sharks have excellent depth perception.
The hammerhead shark also makes eye and head movements as it swims to
provide even better binocular vision and depth perception. These
characteristics give the hammerhead shark an exceptional view of its
undersea world.
References and further information:
- McComb, D.M., Tricas, T.C. and Kajiura, S.M., Enhanced visual fields in hammerhead sharks, The Journal of Experimental Biology, 212:4010-4018, 2009.
- Elasmobranch Research Laboratory
- Nosing Around the Shark's Nose - Neuroscience for Kids
Copyright © 1996-2009, Eric H. Chudler, University of Washington
