The strange cross-eyed squid’s disproportionate eyes allow them to adapt to two different bodies of water in the ocean.
Squid’s left eye is much larger than the right eye, which helps them detect prey or enemies above. Photo: MBARI.
The “cross-eyed squid” is a mysterious ocean creature. They live suspended between two worlds: above is the surface of the sea glistening with sunlight shining through the blue water; Below is the deep water, completely hidden from the light.
Their developed “misaligned” eyes allowed them to see both worlds at the same time.
This squid is born with two identical eyes, but the left eyeball usually grows faster, forming a long tube with bright yellow lenses. This giant left eye is very sharp for looking up, searching for food, or alerting predators swimming above. The yellow color of the eyes filters the light to detect the camouflage of glowing animals, trying to hide in the blue that surrounds them.
Meanwhile, the right eyeball is less than half the size of the left eye. This eye is usually directed downward to scan the light for bright creatures in the deep, dark waters.
“It’s a fascinating demonstration of how they exist between two very different habitats,” said Jon Ablett, senior curator of mollusks at the Natural History Museum in London.
The red dots on the squid’s body are luminous organs, called luminescent cells. Photo: Kate Thomas/Duke University.
The cross-eyed squid (Histioteuthis heteropsis) is no stranger to science, and a research team recently found it during an expedition around the Atlantic islands of Ascension and Saint Helena. They are also known as gem ink when their entire body glows with ruby red spots when exposed to ultraviolet light.
James Maclaine, senior curator of fish at the Natural History Museum, said no scientist had tried to shine ultraviolet rays on deep-sea animals. Mr. Maclaine discovered that several other species had bright red spots, such as the gem squid and the viper; some species, such as the lanternfish, do not.
The red dots are glowing organs, called luminescent cells, that emit blue light when the squid swims hundreds of meters underwater. Since there is no deep-sea ultraviolet light, the luminescent cells do not glow red in the natural environment.
The “soft squid” can use luminescent cells to glow and hide its own shadow. The flickering of the cells could also be a form of communication between the squid and to attract mates or attract prey.