What do you know about Nudibranchs?
Often called sea slugs, these cute, colourful critters would have to be my favourite things to hunt for on a dive. There are over 3000 different types of Nudibranchs and more are being discovered every day. They can be found in all the world’s oceans so it’s more than likely you’ll see a couple on one of your next dives.
They come in all different shapes and size, growing up to 30 cm’s in length and can weigh up to 1.5 kg’s. Now that’s a big slug! The fact that they’re all so different makes them very interesting creatures to study and photograph. I’ve seen ones with mohawks, others with frilly skirts, some with spots or stripes and every neon colour imaginable.
The Nudibranch gets its flashy colours from its food. They are quite fussy eaters and sometimes a species will only eat one type of food. Their diet includes corals, sponges, hydroids, fish eggs and even other Nudibranchs! The bright colours are used as a camouflage and to warn off predators as they are toxic to most fish but not to humans. There is one species, the Glaucus Atlanticus, that eats the Portuguese man-of-war and stores its venom so touching them can result in a nasty sting.
Nudibranchs aren’t the fastest moving animals so they don’t venture too far away from home. They get around on their muscular snail like ‘foot’ and have evolved into hermaphrodites (having both male and female reproductive organs) to increase their chances of mating if they happen to come across another Nudibranch. The eggs are usually bright red and spiral shaped; you’ve most probably seen them on a dive before.
Their eyesight isn’t the best either so they use their little tentacles to smell and see the world. The lifespan of a Nudibranch ranges from a few weeks up to a year, depending on the species. Such a short time but I’m sure they make the most of it!
One very cool thing about some Nudibranchs is that they can use the sun to get nutrients from the algae that they eat. They store the chloroplasts and use photosynthesis to get the nutrients, which can sustain them for months. Solar powered slugs!
So keep your eyes peeled for these lovely little creatures on your next dive, you may even see one that hasn’t been identified before! Happy hunting.
Story and photography by Kelly Luckman