Why do some sea slugs have bright colours?

Some sea slugs and other gastropods exhibit bright, conspicuous colours as a form of aposematism, or warning coloration.12

This biological strategy serves as a visual signal to potential predators that the organism is dangerous, toxic, or distasteful. By advertising their noxious nature, these animals can deter predators from attacking, which is advantageous because it prevents the slug from risking injury during a potential encounter.32

In many cases, these slugs secrete harmful chemicals or possess distasteful acids in their mantle cells that make them unappealing to eat. Because predators often learn to associate these vivid patterns with a negative experience, they typically avoid sampling the animal again. Additionally, some sea slugs utilize camouflage or frightening coloration to confuse or distract aggressors, further enhancing their survival in the wild.143