How do nudibranchs use cnidarian stinging capsules for defense?

Nudibranchs utilize the stinging capsules of their cnidarian prey—known as nematocysts—as a sophisticated defensive mechanism. When a nudibranch consumes cnidarians such as sea anemones or hydroids, it is able to ingest certain types of immature, undischarged cnidae without triggering them.12

These ingested cnidae are then sequestered and matured within the nudibranch’s body. They are typically stored in specialized, often lacy, outgrowths on the nudibranch's back called cerata. When the nudibranch is threatened by a predator, it discharges these stolen nematocysts from the cerata to ward off the attacker. This remarkable adaptation allows the nudibranch to repurpose the cnidarian's own complex, toxin-injecting defense system for its own protection.1345