More Than Macro-Size Beauty: Giant Nudibranchs
If you have ever seen your dive guide go crazy over something that at first glance looked like a grain of rice, then congratulations, chances are you have been in the presence of a nudibranch!
But not all nudibranchs are minuscule. Did you know that the largest nudibranch in the world is the Spanish Dancer? It’s native to the Indo-Pacific Ocean and can reach over 40 cm in length!
Nudibranchs get their name from the Latin nudus or “naked,” and the Greek brankhia, or “gills.” They are considered a type of sea slug; however, this classification doesn’t do their incredible looks justice.
Spectacular Nudibranchs
Nudibranchs come in so many fascinating shapes and striking colours. There are over 3000 recorded nudibranch species, and more are discovered all the time. They’re found in all oceans of the world, and while most nudibranchs only grow to a few centimetres in length, there are some true giants as well.
Here are five species of nudibranch that you don’t need a microscope to admire!
Spanish Dancer (Hexabranchus sanguineus)
First on our list is a beautiful nudibranch of truly super-sized proportions – the largest Spanish Dancer officially recorded was nearly 60 cm long, and even bigger individuals have been reported over the years. Primarily active during the night, the Spanish Dancer feeds on sponges and tunicates, whose toxins it stores in its own tissues to deter predators.
The Spanish Dancer gets its evocative name from its fantastic swimming display. To propel itself through the water, the Spanish Dancer moves its body with a series of undulating motions, reminiscent of the movement of the deep-red skirt of a Flamenco dancer.
Size: 40 cm and up
Distribution: From Africa (including the Red Sea) to Hawaii and from Southern Japan to Australia
Giant Dendronotus (Dendronotus iris)
.jpg){kind=link}
This fellow is called the Giant Nudibranch for a reason! Dendronotus iris can grow up to 30 cm in length, and its prominent cerata (the tendrils on its back) make it look even more formidable. Dendronotus iris prefers colder waters. It lives in muddy subtidal areas and can be found as deep as 200m.
Like many nudibranchs, Dendronotus iris is a predator, albeit a very specific one. It feeds solely on the tentacles of a species of tube-dwelling anemone, whose toxins it repurposes and stores for defence. This diet also results in their white, grey, orange, and red colours.
Size: up to 30 cm
Distribution: Along the west coast of North America from Alaska to Baja California.
Giant Orange Tochui Nudibranch (Tochuina gigantea)
Tochuina gigantea is well-deserving of its name, growing to a whopping 30 cm in length, weighing up to 1.4 kg. With its dazzling display of bright orange or yellow, this nudibranch is not one to be missed easily! Not to be mistaken for the similar-looking but much smaller Orange-Peel Doris, the Giant Tochui is mainly found in colder waters.
T. gigantea preys on hydroids, sea pens, and some soft coral and gorgonians species. This is one of the few nudibranchs that occasionally end up on menus. Despite its store of toxins, it’s considered a delicacy by the people of the Kuril Islands. It can be eaten both raw and cooked.
Size: up to 30 cm
Distribution: In the North Pacific from Northern Japan, the Kuril Islands (in the Russian Far East) to Alaska, Canada, and south to California.
Enjoying this post? Tell your friends! Ocean Pulse is a global newsletter for divers, by divers.
White-lined Dirona aka The Frosted Nudibranch (Dirona albolineata)
This brilliant living crystal, Dirona albolineata, is a large nudibranch found in the cold waters of the Eastern Pacific Ocean. Dirona albolineata can be pure white, reddish, rose pink, pale orange, or even a deep lavender. The bright lines that appear to glow along the edges of its cerata make this nudibranch an exciting subject for photographers.
Making its home in the coastal shallows where you can find it all year round, Dirona albolineata is an active hunter, feeding on tiny invertebrates such as bryozoans and shrimps hydroids, and ascidians. It can even crack the shells of small snails, which are among its favourite prey.
Size: up to 18 cm
Distribution: Along the Pacific coast of North America from Alaska to California, and along the coastlines of Russia and Japan in the Western Pacific.
Variable Neon Nudibranch (Nembrotha kubaryana)
Although it is the smallest nudibranch on our list of just over 12 cm, the incredible glowing colours of the Variable Neon Nudibranch more than makeup for its relatively diminutive size. Found in the Western Indo-Pacific island shallows, this nudibranch is also a photographer’s favorite.
N. kubaryana primarily feeds on ascidians (tunicates and sea squirts), including the green-ringed ascidian, which helps to give it its stunning neon green colour. Like many nudibranchs, it stores the toxins from its prey as defence, secreting a slimy toxic mucous when threatened.
Size: over 12 cm
Distribution: Western Indo-Pacific (including East Timor, the Phillippines, and Indonesia). Also been reported along the coast of East Africa, including Madagascar.
Honourable Mention: The Spanish Shawl Nudibranch (Flabellina iodinea)
.jpg){kind=link}
Okay, at a mere 5 cm, this is not a giant nudibranch, but I challenge you to miss this beauty moving across the substrate! Flabellina iodinea preys on certain hydroids, whose pigments give the nudibranch its striking colours.
Size: 5 cm
Distribution: From Mexico to British Columbia, Canada. Also, in the Galapagos Islands and the Gulf of California.
Find Amazing Nudibranchs Around the World!
Nudibranchs are not only found in exotic tropical locations but seas all over the world. There are fabulous nudibranchs from the warm waters of the Caribbean to the chilly cliffs of Vancouver Island, the English Channel, and beyond. In fact, many large nudis, such as the Giant Orange Tochui, tend to prefer the colder regions.
Nudibranchs are not limited in their range of depths either, with some species making their home in just a few meters of water, while others can be found in depths beyond 700m.
What is certain is that wherever you are in the world, make your way to the coast, and you could find many species of nudibranch waiting for you, from the microscopic to the gigantic.
Enjoying Ocean Pulse? Subscribe for more stories for divers by divers.
About the Author
Alexandra fell in love with the underwater world when she was ten years old. A fish ID expert and keen marine conservationist, she is now a PADI Master Instructor with 12 years of experience working in the Caribbean.
Do you love Nudibranchs as much as we do? Be sure to let us know in the comments!
 | A guest post by
|