Nudibranchs are on of the most colourful creatures on earth. As such, they are a snorkellers and scuba divers' obsession and are an awesome target when exploring under the sea. While they are hard to find, their discovery is always a great surprise.
The nudibranch's amazing colours, which are different in every one of the 3000 species, indicate a poisonous nature. Although these magnificent creatures don't make their own poison, but gather ("steal") it from the poisonous animals they feed on. Divers and snorkellers should look carefully to find these colourful critters, which are often spotted amongst the soft corals.
Nudibranchs are a soft bodied mollusc, and look similar to a colourful slug. Their anatomy may resemble the texture and colour of the surrounding plants, allowing them to camouflage, in hopes of avoiding becoming someone's dinner. Others have an intense and bright colouring, which warns that they are distasteful or poisonous so that they will not be eaten. They don't actually produce their own colouring, instead absorbing pigments from the foods that they eat. Several species can even make noise, producing a tapping-like sound which can be heard by the human ear.
Nudibranchs are found in warm, tropical waters and spend their lives in the shallows. The largest species can grow up to 30cm and weigh up to 1.5kgs, but they can be at small as 1.5cm. While they only live to be about a year old, they'll spend their whole lives foraging for food, moving up to 10m a day.
The nudibranchs possess both male and female organs, meaning any individual can mate with any other individual of their species. When mating, they fertilise each other and both will lay a beautiful round pattern of eggs that you can sometimes spot on the reef. This ring of eggs is a good indication that there is a nudibranch around.
Nudibranchs are carnivorous. Some feed on sponges, fish eggs, sea slugs, hydroids, or bryozoans, and some are cannibals, eating other sea slugs, or, on some occasions, members of their own species. There is also a group that feeds on and barnacles, while some feed on anemones. They find their food by using tentacle-like horns on the top of their head, which they use to feel, taste and smell. They eat the prey they find by using small teeth and digestive enzymes, which break down their food.