Diverticula is an anatomical term for a set of organs which are visible from the outside on a group of sea slugs known as nudibranchs, which are marine opisthobranch gastropod molluscs.
These diverticula are located within the cerata of a nudibranch and they are parts of the digestive gland of the animal. Because the nudibranch's skin is translucent, the contents of the diverticula are easily visible; this means that the nudibranch automatically takes on the exact colour of whatever substrate and food source it is living on and feeding on (for example, sea anemones, hydroids, etc). Because of this, visually the animal blends perfectly with its environment, providing excellent camouflage.
The diverticula are also important because they pass any intact nematocysts (which have been ingested from the food source) along to the tips of the cerata, where these stinging cells are then available to defend the nudibranch against predation.