Sea slugs use a variety of means to defend themselves from predators. Most of the Armina species, like that in the upper left, bury themselves for a portion of the day or night to hide. To the right of that Cerberilla affinis has shed some of its cerata (those projections on its back), rather the way a lizard can shed its tail, giving the animal a chance to get away. Plocamopherus imperialis, at middle left, flashes a startling bluish light if it is disturbed. , Jorunna funebris, at middle right, is covered with glass-like spicules…any fish biting it will get a mouth full of stickers. Many of the Dorid slugs like this Glossodoris cincta can emit foul tasting chemicals from pores along the edge of their “skirt” or mantle.
The slug at the bottom right has a way to use the stinging cells, or nematocysts, from their prey. Flabeliina exoptata and other Aeolids consume nematocysts when eating corals, anenomes and hydroids. They do not digest the stinging cells but store them in the tips of their cerata and deploy them against their own would-be predators. Stored nematocysts must be refreshed every 5 days.