This massive group of marine Gastropods consists of almost 2,500 individual species that inhabit all oceans and seas from tropical to temperate to Arctic and Antarctic waters.
The name Nudibranch refers to ‘naked gills’ as Nudibranchs have their gills exposed on their backs. Each species of these amazing little guys is a highly evolved specialist in his native environment. They have developed intricate camouflage systems of not only colour adaptations but also cerata (appendages) that closely match various host corals.
The astounding colouration is vital in not only hiding the Nudibranch from predators but also as a warning sign indicating that they are unpleasant (at the very least) to eat. Some Nudibranchs deliberately consume the nematocysts of their prey corals and in turn, become toxic to predators. There are others that digest zooxanthellae and utilize it in the very same way that corals do….providing an alternate food source to the Nudi.
Be aware though, that not all (not many) Nudibranchs prey on corals…there are many that eat bryozoans and ascidians, sponge, algae, tunicates, hydroids and other micro-marinelife. They life fast and die young with most of their kind only living for a very short time. Apart from the pitfalls, many Nudibranchs make for excellent aquarium inhabitants if you are sure of and have access to its preferred food.