Nudibranchs are mollusks that have evolved without a hard, protective shell. Many species have compensated by evolving a toxic poison. Their bight colors serve as a warning to predators that these tasty-looking snacks are not to be messed with. The toxins in their bodies makes them taste bad. This allows them to survive in spite of the fact that they are slow-moving targets with no hard defensive shell. Nudibranchs can be found all over the world's reefs in thousands of different shapes and colors.