Slender Facelina

• It digests hydroids without setting off their stinging cells and moves them intact to the tips of its cerata, where it uses them for its own defence.
• The ringed rhinophores on its head serve to track its prey by chemical scent.
• It steals its prey's weapons. It eats hydrozoans and, instead of digesting their stinging cells, keeps them intact and moves them into sacs called cnidosacs, at the tips of the cerata on its back.
• From there it can fire them again at an attacker as though they were its own. The phenomenon is known as kleptocnidae.
• So that it can collect them without poisoning itself, the front part of its gut is lined with chitin, which deflects the stings.
• The cerata are not just an armoury: they also serve for breathing, taking up oxygen across their surface.
• It has been suggested that some nudibranchs eat hydrozoans precisely to keep their cnidosacs loaded, rather than for food.

Skeleton type

Invertebrate - no rigid skeleton (mollusc)

Habitat and environment

Rocky bottoms with hydroids of the north-eastern Atlantic and the Mediterranean

Sources consulted: Wikipedia (es): Facelina auriculata · anatomia de Gastropoda