What is cnidosac?

cnidosac meaning a sac located in a ceras of a nudibranch gastropod which contains undischarged nematocysts (obtained through feeding upon cnidarians) passed from the slug’s digestive system. When a predator attacks the nudibranch, the nematocysts may discharge as a defensive mechanism

Image of tissue section showing cnidosac
Section through the ceras ofAeolidiopsis ransonishowing the cnidosac with three nematocysts. (Photo: Dr. Bill Rudman)


reference: Coral Reef Information System – Glossary