Squid Can Survive Twilight Zone In Ocean Thanks To Mismatched Eyes


Histioteuthis heteropsis is the scientific name for the cockeyed squid which is also known as the "strawberry" squid due to its uncanny resemblance to the fruit.

Experiments have been conducted on this strange-looking creature and reveal why the creature has mismatched eyes.

During the research, nearly 150 sightings from under the sea were captured on video by biologist Kate Thomas, a fellow student at the Monterey Bay Aquarium Research Institute (MBARI). These videos showed the squids moving around in the water and also provide deep insight into why they have lopsided eyes.

The researchers have deduced that the larger eyes are mainly suited for gazing upwards, looking for silhouettes of other little or big sea inmates. The smaller eye, on the other hand, are for gazing downwards, which assists the squid to scan the deep dark waters for "flashes of bioluminescence."

This squid specie is usually found in the "twilight zone" or mesopelagic zone, which is around 200 to 1000 meters below the water's surface.

The Research

Thomas's videos recorded more than 150 sightings of Histioteuthis heteropsis and around nine sightings of Stigmatoteuthis dofleini, the smaller version of Histioteuthis heteropsis.   

She noted that since the squids move in a vertical direction, they usually appear upside down to the humans with the big eyes constantly looking upwards and the smaller one looking down.

The larger eye angled upwards is the one which picks up the silhouette of objects against the sun's light that penetrates the water's surface. Thomas believes that this is why the upper eye is larger, because it needs to properly detect the light and the shadows.

The lower eyes though are angled in such a way that there is no possibility of seeing shadows and silhouettes. This lower eye is mainly associated with detecting bioluminescence.

"And once it is looking for bioluminescence, it doesn't really need to be particularly big, so it can actually shrivel up a little bit over generations," explains Thomas on why the lower eye is smaller.

The study has provided some surprising leads into how evolution has managed to create the perfect creature for such an inhospitable region deep below the surface of the ocean. The cockeyed squid seems to employ just the kind of resources that it needs and nothing more.

"You want eyes just big enough to do what you need to do, but you don't want to have any bigger eyes because then you are just wasting resources," stated Thomas.

The results from the MBARI research have been published in the journal Philosophical Transactions B.

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