Shapeshifters Of The Med: The Incredible Powers Of Nudibranchs

A creature that can take on the skills of whatever it eats sounds like a freaky monster out of a horror show like Supernatural. But what if we told you that those creatures not only exist, you can even meet them (and they’re cute!)

We are, of course, talking about nudibranchs. To put it very simply, they are underwater slugs. Sounds a lot more boring now, doesn’t it? But don’t be fooled, they are nothing like the slugs that are nibbling on the lettuce in your garden.These little miracles come in so many different shapes and colors that they are often referred to as “Underwater Pokémon” and even though they look incredibly cool, their looks are the least interesting thing about them!

Nudibranchs are like (very tiny) shapeshifters; they have the almost supernatural power of adapting their bodies to look like their prey and they can absorb their prey’s special skills to use them for themselves.

One of our absolute favorites is the pink flabellina (or flabellina affinis). Pink flabellinas feed on Hydropolyps, which are sessile animals with stinging cells that are pretty harmful to most organisms. Not for the flabellinas though, those nudis happily munch on the Hydropolyps and then store their stinging cells in the spikey looking cerata on their back as a defense against predators. They even use their prey as “bodyguards” for their eggs by laying spirals of eggs around the Hydropolyps, knowing that harmful organisms would get stung by them.

Pink flabellinas are – surprise – hot pink and grow up to 4 centimeters, which makes them easy to spot whether you have experience searching for nudibranchs or not. We even have a special dive spot that we like to call flabellina heaven because we always see lots of flabellinas there!

Let’s talk about another incredibly cool nudibranch – the green Elysia (or Elysia timida). These ones are a lot harder to spot since they grow to a maximum of 1.2 centimeters. They are white with tiny red dots and can be found on algae-covered rocks as algae is their preferred food. Green Elysias practice kleptoplasty. That means when they eat algae, they don’t digest its chloroplasts but store them in their back, where they continue to photosynthesize and provide the nudibranch with sun energy. The Elysia can regulate how much sun the chloroplasts receive by opening or closing the parapodia on their backs. If you look closely, you can see the green color of the chloroplasts.

Besides nudis that steal stinging cells and chloroplasts, there’s also those that steal toxins, such as the giant doris (or Felimare picta). The giant doris can reach up to 19 centimeters, so their size makes them easy to spot, but they are incredibly rare to find. Their diet consists of a selection of sponges which produce toxins to protect themselves from predators, but the giant doris is unaffected and unbothered by those toxins. Instead, it recycles the toxins to use them as its own form of protection. Surely not what the sponges had in mind!

If you want to spot those underwater Pokémon for yourself, just join us for some fun dives and make sure to tell your guide that you’re on the lookout for nudibranchs, we’d love to help you search!