Quirks & Quarks

Why do these tiny squid have two completely different eyes?

Cockeyed squids' wonky eyes help them survive in the ocean's low light 'The Twilight Zone'.
Histioteuthis heteropsis (Cockeyed squid) in the deep waters of Monterey Bay. (2012 MBARI)

Down in the depths of the Pacific Ocean known as the 'twilight zone,' lives a family of weird looking squid with mismatched eyes. One eye is flat and black. The other eye is bulging and yellow. 

Duke University biologist Katie Thomas wanted to find a reason for the mismatched eyes. While interning at the Monterey Bay Aquarium Research Institute, she combed through over 25 years worth of deep sea footage. 

The Twilight Zone: Meet the squid with mismatched eyes

6 years ago
Duration 1:05
The Twilight Zone: Meet the squid with mismatched eyes

She discovered that these squids' eyes are adapted to two different light sources. The smaller black eye mostly looks down to keep an eye out for high-contrast flashes of bioluminescence. The larger, yellow eye tilts upwards to keep an eye on the dark, dim water above. The bigger eye has increased sensitivity to faint sunlight from above. And it's yellow to filter out the colour blue, so it can better detect prey and predators above. 

Additional Links: