Nudibranch means naked gills
The name comes from words meaning naked gills. Many species have visible external gills rather than hidden breathing structures.
Nudibranchs are small, colourful, strange and often surprisingly difficult to identify. These ten basics are a good starting point for divers, photographers and anyone beginning to look more closely at reef life.
They are sea slugs
Nudibranchs are marine molluscs. Unlike most snails, adult nudibranchs do not carry an external shell.
There are thousands of species
More than 3,000 species are known, and new ones are still described, especially in rich areas such as Indonesia and the Philippines.
They are hermaphrodites
Each individual has both male and female reproductive organs, but they still normally need a partner to reproduce.
Egg ribbons look like flowers
Many species lay delicate ribbon or rosette-shaped egg masses that can look like tiny underwater roses.
Many live short lives
Some nudibranchs may live for months rather than years, making every encounter feel a little more special.
Sizes vary dramatically
Some are only a few millimetres long, while the Spanish Dancer can grow large enough to be seen easily by any diver.
They are carnivores
Many feed on sponges, hydroids, anemones, corals, tunicates and sometimes other nudibranchs.
Some borrow defences
Certain nudibranchs can store chemicals or stinging cells from prey and use them as protection.
Colours have a purpose
Bright colours can provide camouflage, warning signals and protection rather than simply decoration.
Back to Nudibranchs
Return to the Nudibranchs Academy section to explore anatomy, behaviour, identification, life cycles, food sources and hotspots.
Return to Nudibranchs