The Hawaiian bobtail squid creates its own light, using special organs filled with glowing bacteria. But these organs don’t just produce light – they sense it too. They are loaded with proteins that can detect light, and they produce nervous signals in bright conditions. They can expand and contract like an iris to control how much light gets through. They’re covered with a thick, transparent tissue that acts like a “lens”. The light organs are effectively an extra set of primitive eyes. They are living, ‘seeing’ flashlights. (Image by William Ormerod)

Read more: Glowing squid use bacterial flashlights that double as an extra pair of “eyes”