Nudibranch

Nudibranchs belong to a group of animals called gastropods (which means stomach foot), and is comprised of slugs and snails from saltwater, freshwater and from land! Best known for their extraordinary range of colours, patterns and shapes, these often-tiny creatures are a favourite of divers and photographers. There are more than 3,000 known species of nudibranch, and new ones are being identified almost daily.

Nudibranch, meaning ‘naked gills’, describes the feathery appendages on the outside of their body that have replaced internal gills. These external gills should not be confused with the two small tentacles on their head, which resemble antennae in some species. These tentacles are used as chemical sensors to ‘smell/taste’ chemicals in the water.

Found throughout Western Australia, nudibranchs are carnivores, feeding on animals such as sponges, soft and hard corals, anemones and hydroids. Without a shell for protection, some species are able to repurpose the stinging cells (nematocysts) from their diets to use as defence, with their bright vibrant appearance also an indicator to predators that they are poisonous.

All nudibranchs are ‘hermaphroditic’, which means the same animal acts as both male and female. Reproducing as a mating pair, the nudibranchs exchange sperm sacs through a tube. Each nudibranch will then lay egg masses that can contain millions of eggs.