A bioluminescence expert catches a jumbo squid on camera for Blue Planet II

How do you catch sight of a jumbo squid deep underwater? Travel down in a submersible, use red light to see—most deep-sea creatures can’t see red light—and then, to attract larger predators, flash the ‘SOS’ light pattern of a bioluminescent jellyfish with a ring of blue lights.

In this BBC Earth Unplugged clip, marine biologist and bioluminescence expert Edith Widder explains this shift toward inconspicuous deep sea exploration, and demonstrates her innovative camera system and lure—the Eye-in-the-Sea. This concept is how she first caught footage of a jumbo squid on camera in 2004, and more recently for Blue Planet II. More from Scientific American:

Widder created an electronic jellyfish that mimics the light shows of living bioluminescent jellyfish using a circle of 16 blue LEDs that flash in patterns. Specifically, the robot jellyfish mimics the atolla jellyfish (Atolla wyvillei), which employs light displays as a distress call when confronted by predators, signaling for even bigger predators to interfere and possibly rescue them. Her idea is that the robo-jelly would attract these same big marine predators to the camera…

In 2004 Widder deployed the camera in the Gulf of Mexico. What she discovered there proved beyond a doubt how effective the Eye-in-the-Sea could be when paired with its electric jelly companion.

Fish swam up to and all around the underwater camera completely undisturbed. After four hours of collecting footage, Widder switched on the electronic jellyfish, which began its pinwheel light show. A mere 86 seconds after it started glowing the robot attracted a squid around two meters long—a species that no scientist had ever documented before. Widder thinks this is exactly the kind of big marine predator a living bioluminescent jellyfish might attract when under attack by smaller predators, in the hopes of saving itself.

Read more about Widder’s work in this article by Ferris Jabr.

Next: 1000m beneath the Antarctic ice, where no human has gone before. Plus: A never-before-seen bioluminescent jellyfish in the Mariana Trench, three quarters of deep-sea animals are bioluminescent, and more videos about bioluminescent animals, both in and out of the water.