14 Fun Facts About Nudibranchs

Nudibranchs, also known as sea slugs, are some of the most colorful creatures in the ocean. Whilst some species may look similar to land slugs, they are much more vibrant and come in a variety of shapes and sizes. These critters are not only beautiful to look at but have plenty of quirky characteristics which aid them in eating, mating and protecting themselves from predators. Look past their unique exterior and read on to find out our favorite fun facts about nudibranchs.

Fun Facts About Nudibranchs

  • Nudibranchs are also known as sea slugs and are part of the mollusca family. This group of animals are known for their soft invertebrate bodies that are sometimes protected by shells. Other animals of the mollusca family include snails, clams and squids.
  • Nudibranchs start life with a shell as larvae, as they continue to develop into adults they break free of this shell. The hatching time of nudibranchs varies between species but once mature nudibranchs can live up to a year, though some will live for less than a month.
  • There are over 3000 different species of nudibranchs. You can find dive locations with 100 of species in a small area. Within species there are different variations so you are likely to always see something new on each dive.
  • Whilst there are thousands of species of Nudibranchs there are two main types, which are characterized by their breathing apparatus. The aeolid nudibranch has soft spikes covering its body which help it absorb oxygen whereas the dorid nudibranch has a plume of gills around its anus.
  • Nudibranchs have two outward facing nostrils known as rhinophores, they look similar to horns sticking out from the nudibranch. These rhinophores pick up scents in the water which helps them navigate their surroundings and find food and other nudibranchs. These rhinophores are particularly helpful as nudibranchs have terrible eyesight.
  • Nudibranchs are carnivores, their prey includes anemones, coral, algae, sponges and even other nudibranchs. Some nudibranchs are very specific regarding their diets and will only eat one type of food.
  • Nudibranch get their color from the food they consume, eating the coral and anemones of their habitat gives them the same coloring making it easier to blend in.
  • Nudibranchs have two different ways of digesting food which varies by species. Some nudibranchs have a beak and tooth covered tongue they use to scoop food from rocks. Other nudibranchs suck in their food after pre-digesting its tissue with enzymes.
  • Nudibranch predators include sea turtles, fish, sea stars as well as other nudibranchs. Pollution, habitat loss and overfishing are all a risk to nudibranch species.
  • As nudibranchs cast away their shells when they are young they have come up with some interesting alternative defense mechanisms. Some species use camouflage to hide from predators. Others use brightly coloured exteriors to warn predators of their unsavory taste in an effort to deter them from attacking. Certain species are even able to absorb the stinging properties of their food as a form of protection.
  • Nudibranchs are solitary creatures, if they want to mate, they must seek out another nudibranch by following its scent. Fortunately, nudibranch are hermaphrodites meaning no matter what sex the other nudibranch is they will be able to mate.
  • Nudibranchs mate by lying next to each other and connecting their reproductive organs. In some species the reproductive organs will snap off during colitis, but they can grow it back. Once fertilized the nudibranch will expel its eggs into beautiful ribbons or rosette like shapes.
  • Nudibranchs are small animals, the smallest species is the Dotos which are usually less than 0.5 inches/15mm long. The largest species is the Spanish Dancer which can grow up to 16 inches/40 cm.
  • Nudibranchs can be found all over the world, they are almost exclusively a saltwater animal. The largest number of nudibranch species live in tropical, shallow waters near reefs.

Eager to learn more facts? Check out these 20 Amazing Facts about octopuses.

Eye catching nudibranchs

Nudibranchs are fascinating creatures but it is their varied appearance that makes them a favorite among divers. While they are masters of camouflage they can be spotted with a keen eye and slow pace. Here are a few of the most eye-catching and interesting looking nudibranchs out there.

The Blue Glaucus also known as Blue Dragon, species of nudibranch swims upside down near the water’s surface and has dramatic blue shades as well as plenty of spikes. They enjoy eating the organisms known as Portuguese man of war and are a rare species to spot.

You might double take if you see an Eastern Emerald Elysia as its body is similar to a leaf as it has vibrant green coloring. Not only does it share its appearance with a leaf but it can photosynthesize like a plant too.

Hexabranchus Sanguineus or as it is commonly known the Spanish Dancer is not just interesting in its blood red appearance but in the way it moves through the water. Wiggling its body in order to propel it through the ocean, they are also the largest nudibranch species meaning even when still they will catch your eye.

Covered in brightly coloring spines, the Janolus nudibranch stands out. Whether combing the rocks for food or rolled up in a ball to deter predators this tiny critter will draw you in for a closer look.

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Where to find nudibranchs

Nudibranchs can be found in waters all over the world, from the freezing temperatures of the arctic to warm tropical reefs in the Indian Ocean. They come in all shapes, sizes and colors. There is a chance of seeing a nudibranch on any dive but some locations promise plenty and unique nudibranch discoveries.

You are sure to find plenty of Nudibranch throughout the Philippines with expansive dive locations but Anilao is considered by many to be the Nudibranch capital. Within this area not only are nudibranch in plentiful numbers but there are over 100 different species which inhabit these waters. Discover the tiny colored spines of Flabellina Exoptata, the spotted dorid Goniobranchus Hintuanensis and plenty of ribboned nudibranch eggs.

If you are heading to Indonesia then the waters of the Lembeh Strait in Northern Sulawesi are thriving with nudibranch activity. Broken coral sea bed and sloping reefs make for perfect dwellings for over 200 species of nudibranchs. Macro photographers will be in awe of the photogenic Chromodoris Elisabethina species, the unusual Halgerda Batangas and brightly coloured Aegires Minor.

In the waters of the Indian Ocean off the coast of Kenya at Diani Beach you will also discover a world of nudibranch species. Kenyan waters are not as well explored as other dive locations so there are plenty of surprises to be found in the nudibranchs found here. Find species including Ceratophyllidae Africana, Goniobranchus Alius and Hypselodoris Yarae on the east african coast.

Check out our 9 Best Dive Spots in the Middle East and Africa to plan your next diving adventure.