Nudibranchs are a colourful and varied group of molluscs. In fact, they are sea slugs that have gotten rid of their shells. Instead, they protect themselves by being distasteful or poisonous. The colour is in fact a warning sign. They want to be noticed and avoided.
Nudibranchs are benthic predators. Their diet consists mainly of sponges, hydroids, and other small creatures from the bottom. Many can collect the poison from other animals even the entire living cells with the poison and use them for their own defence.
About three thousand varieties of nudibranchs have been discovered. However, we have little information about the number of species here in Iceland, as they have not been studied here at all.
The name nudibranch comes from both Latin and Greek, nudus meaning bare and brankhia meaning gills. Either Nudibranchs breathe through their skin or they use the tuft of secondary gills many species carry on the tail end of their back. Nudibranchs are hermaphrodites, that is they have the organs of both sexes, but cannot fertilize themselves