Some sea slugs steal jellyfish stingers.

Nudibranchs are colorful sea slugs, and some species have the ability to steal the stinging cells of the animals they eat and use them against their own predators. These nudibranchs feed on aquatic invertebrates such as jellyfish, coral, and sea anemones that use microscopic capsules called nematocysts to sting attackers. The nudibranchs possess adaptations that protect them from those stings while they feed, allowing some undischarged nematocysts to survive digestion intact and to be stored for later use.

When a predator takes a bite of a nudibranch, the nematocysts can fire, giving the attacker a nasty surprise. Scientists are still studying exactly how these sea slugs prevent the stingers from firing during digestion and safely store them for later use. Nonetheless, it’s an unusual defense that lets a sea slug turn its dinner into ammunition.