13 in a special issue of the journal Philosophical Transactions B.Īlso known as the strawberry squid for its bright pink color and smattering of seed-shaped photophores, Histioteuthis lives in a region of the ocean known as the mesopelagic or "twilight" zone, 200 to 1000 meters below the surface. With one large eye adapted for seeing the shadows of fellow sea creatures, and a second small eye adapted for spotting bioluminescent flashes, it makes optimal use of meager illumination. Credit: Kate Thomas The cockeyed squid Histioteuthis heteropsis has evolved an ingenious solution to a deep-sea ocular conundrum. "In the case of the Histioteuthis, this cockeyed squid, they chose one eye for each." "The deep sea is an amazing natural laboratory for eye design, because the kinds of eyes you need to see bioluminescence are different from the kinds of eyes you need to see the basic ambient light," said Sönke Johnsen, professor of biology at Duke University and senior author on the study. These observations, combined with visual simulations, indicate that the large eye is specifically adapted for gazing upwards, searching for shadows of fellow sea creatures against the rapidly fading sunlight, while the small eye is adapted for gazing downwards, scanning deeper, darker water for flashes of bioluminescence. "You can't look at one and not wonder what's going on with them," said Duke University biologist Kate Thomas.īy watching cockeyed squids glide and pirouette through more than 150 undersea videos collected by the Monterey Bay Aquarium Research Institute (MBARI), Thomas has gathered the first behavioral evidence that the squids' lopsided eyes evolved to spot two very different sources of light available in the deep sea. Credit: Kate Thomasįrom eyes the size of basketballs to appendages that blink and glow, deep-sea dwellers have developed some strange features to help them survive their cold, dark habitat.īut with one normal eye and one giant, bulging, yellow eye, the "cockeyed" squid Histioteuthis heteropsis has perhaps the strangest visage of all. The cockeyed squid Histioteuthis heteropsis, also known as the 'strawberry' squid for its pink color and smattering of seed-like photophores, has evolved a mismatched set of eyes: one large eye for seeing the shadows of fellow sea creatures above, and a second small eye for spotting bioluminescent flashes below. Mismatched eyes help squid survive ocean's twilight zone heteropsis was exhibited publicly for the first time at the Monterey Bay Aquarium on June 27, 2014. They are slow and not easily scared, even by submersibles. It is thought that the large eye is used to spy for food and predators in the down-welling light above the squid, while the smaller eye peers into the darkness below, seeking out bio-luminescent signals. These squid are named for their peculiar set of differently sized eyes, one being small and blue and the other being large and yellowish. Histioteuthis heteropsis, the Cock-eyed Squid, also known as the Strawberry Squid, is a species of cock-eyed squid. But the eye looking up actually does benefit from getting a bit bigger," he added.Strawberry Squid - Histioteuthis heteropsis 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. There is no way it is able to pick out shapes against the ambient light. "The eye looking down really only can look for bioluminescence. “The deep sea is an amazing natural laboratory for eye design, because the kinds of eyes you need to see bioluminescence are different from the kinds of eyes you need to see the basic ambient light," said senior author Sönke Johnsen, Professor of Biology at the university. The small eye, on the other hand, gazes slightly downwards looking for flashes of bioluminescence.Ī paper about the discovery was published in the recent issue of Philosophical Transactions B journal. It was then she realised that the squid's eyes had evolved to its present state so as to take advantage of the two different sources of light available in the deep sea, where the squid lives: The large eye is adapted for gazing upwards, looking for the shadows of animals against the sunlight. So she reviewed more than 150 videos of cockney squids collected by the Monterey Bay Aquarium Research Institute. This was what Duke University biologist Kate Thomas discovered when she started investigating the purpose of the mismatched eyes. It turns out that their mismatched eyes is actually an ingenious hunting strategy. They drift through the sea in a near-vertical orientation, with its head “pointed” downwards, with its larger eye directed slightly upwards and its smaller eye directed slightly downwards. Also known as the strawberry squid, they live in the mesopelagic or twilight zone of the ocean, some 200 to 1,000 metres below the surface.
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