Octopuses and squids can switch camouflage mode to stay invisible in the twilight zone

There are two ways of becoming invisible: you can either be transparent so all light passes through your body, or you can blend in by taking on the colours of your surroundings. A truly incredible animal would be able to do both, switching between the two at a whim. And that’s exactly what some squids and octopuses can do. Sarah Zylinski and Sonke Johnsen from Duke University found that two cephalopods – the octopus Japetella heathi and the squid Onychoteuthis banksii – can switch their camouflage strategy depending on how bright their environment is. When sunlight streams from above, they choose the see-through option. When their world darkens, they go for darker colours that blend in. Both species live in the twilight zone, a band of water between 600 and 1000 metres down. Sunlight only just grasps at this world, which teeters on the edge of total darkness. The animals ...