In humans the “eye-teeth” are the upper canines, but new research suggests that the world’s biggest fish have eye-teeth in a more literal sense.
Whale sharks have been found to have tooth-like scales all over their eyeballs, a feature not noted before in any other vertebrate but, in the absence of eyelids, thought to keep the eyes safe from harm.
The Japanese researchers who have just reported on the finding say that whale sharks have evolved an eye covering made from tough “dermal denticles” similar to those that cover their entire bodies, and those of other sharks and rays.
These tiny scales are similar to teeth, based on a pulpy core encased in the bony tissue known as dentine, with an enamel-like outer coating. Designed for abrasion resistance, they offer protection against potential damage from “mechanical, chemical and biological hazards”.
Until now scientists had assumed that vision was unimportant for environmental perception in whale sharks, basing this on the small size of their eyes in relation to the body, and the small section of the brain allocated to sight. The level of protection afforded to the eyes now seems to suggest the opposite.