Investigate the Giant Squid: Mysterious Cephalopod of the Sea
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Sneaky Squid
Jeanna Bryner  

It's no secret: Many fish can glow using bioluminescence (light made by a chemical reaction in living tissue). But now, researchers have discovered special tissues that make the built-in nightlight of one tiny squid extraordinary.

The Hawaiian bobtail squid has an organ in its belly that works like a flashlight, says Wendy Crookes, a biologist at the University of Hawaii. The organ is home to symbiotic (mutually beneficial) bacteria. In return for a nutrient-rich home, the bacteria glow. This light helps the squid survive the night in the dark ocean.

To focus the glowing light, the squid has mirror-like tissues. Crookes discovered that the squid's reflectors are made of unique pro Leins (chains of amino acids) and are unlike any other known reflector.
Amazingly, the squid's flexible proteins can change shape. This helps the squid alter the brightness of its light to hide from predatory fish.

When floating near the water's surface, the squid reflects the bacteria's light; onto the seafloor. Nearby fish mistake their potential snack for moonlight and the squid escapes unharmed.
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