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Feisty squid and deep-sea fish dazzle potential predators with a bioluminescent flash of light

Squid and deep-sea fish blind potential predators with a bioluminescent flash of light that allows them to escape, study shows

  • Elephant seals feast on lanternfish that live in the dark ocean at great depths
  • Biologists set out to find out how seals hunt their prey in the dark
  • They attached trackers and sensors to five seals from the Kerguelen Islands
  • The team discovered that the seals can find food by the glow of the prey
  • However, the bioluminescent animals also use their light to help them survive

Squid and deep-sea fish dazzle potential predators with a bioluminescent flash of light that allows them to escape, researchers discovered.

Biologists examined the dietary habits of elephant seals – which traditionally feast on lanternfish and squids that live in the murky ocean at great depths.

To find out how the seals find their prey in the dark, the team attaches GPS trackers and light-detecting sensors to five seals from the Kerguelen Islands in Antarctica.

They discovered that the bioluminescent glow of their prey allows the seals to hunt – but the glowing animals can also use light to their advantage.

Squid and deep-sea fish dazzle potential predators with a bioluminescent flash of light - depicted in blue - that allows them to escape, researchers discovered

Squid and deep-sea fish dazzle potential predators with a bioluminescent flash of light – depicted in blue – that allows them to escape, researchers discovered

“We know how far [seals] how long, how deep they dive and that they focus on currents and boundaries between oceans where they find prey in large numbers, “says paper author and biologist Pauline Goulet of the University of St. Andrews.

“Bioluminescent organisms are the main source of light – 80 percent – in water deeper than 500 meters.”

These animals produce two forms of light – a continuous dim glow for camouflage from below and dazzling flashes, which experts thought they would use to distract predators.

Ms. Goulet and colleagues wondered if the light would draw the seals to the glowing animals, or scare them off instead.

“Because the bioluminescent flashes are so short, usually less than a second, the tags required a very fast light sensor,” said Ms. Goulet.

The scientists traveled to the Kerguelen Islands in Antarctica – also known as the Desolation Islands – to attach sensors and GPS trackers to five elephant seals.

When the seals returned two months later, the team retrieved four of the labels and found that most animals had started an odyssey of 1,864 miles (3,000 kilometers) deep in the fish-filled areas of the ocean.

However, an intrepid Argentine seal bypassed Cape Horn – traveled 1,429 miles (2,300 kilometers) before localizing fish off the coast of Chile.

By analyzing the seals’ movements and examining over 2,000 bioluminescent flashes captured at a depth of 259-2,359 feet (79-719 m), the scientists confirmed that the flashing animals did indeed use light to deter their attackers .

The scientists traveled to the Kerguelen Islands in Antarctica - also known as the Desolation Islands - to attach sensors and GPS trackers to five elephant seals.

The scientists traveled to the Kerguelen Islands in Antarctica - also known as the Desolation Islands - to attach sensors and GPS trackers to five elephant seals.

The scientists traveled to the Kerguelen Islands in Antarctica – also known as the Desolation Islands – to attach sensors and GPS trackers to five elephant seals.

“The prey always flashes as soon as the seal attacks, suggesting that the flash is a defensive response when the prey realizes it is under attack,” said Ms. Goulet.

The seals quickly stored fish that did not light up, but found it more difficult to catch prey that lighted up unexpectedly.

However, a cunning seal saw the tables turn – deceiving the prey by giving itself away with a subtle movement of its head causing a flash of flash.

“It seems that bioluminescent fish are fighting back by trying to scare their pursuers of elephant seals, but their attackers can also learn to abuse the bioluminescent betrayal of their prey,” Ms. Goulet concluded.

The full findings of the study are published in the Journal of Experimental Biology.

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