Without shells to protect them, nudibranchs must rely on other strategies to discourage predators. The bodies of some nudibranchs produce poisonous or foul-tasting slime that nibbling fish find unappealing. Most of the poisonous species have bright colors that make the clear statement to predators: “I am poisonous—don’t eat me!”
Some species of nudibranchs have the remarkable ability to disarm poisonous organisms and have even developed a technique for reusing their enemies’ weapons for their own protection. Nudibranchs can dine on animals that other predators must avoid, including sponges, anemones, stinging coral, and jellyfish. When a nudibranch consumes an animal armed with nematocysts, the stinging cells pass through its digestive system unharmed and are transported to the dorsal surface and stored under the skin. Here the nematocysts continue to function, protecting the nudibranch from its predators.