The seas, in their immensity, contain a vast amount of life that comes in all shapes and sizes - despite the trash that we humans throw at them.
The big guys, like whales, dolphins, and turtles, have incredibly efficient PR teams. Then there’s the misunderstood, falsely accused, and savagely chased sharks.
But, also, there are a lot of little guys that deserve the same level of attention. In this group of minuscule creatures, the nudibranchs are the underwater Hollywood stars.
What are Nudibranchs?
You may have seen these strange creatures that resemble slugs that have been spending time in a crazy painter’s party on social media sites such as Instagram. Or, if you’re lucky, you’ve spotted them on a dive. Yes, they are slugs, but there is also a bit more in them than that. They are sea slugs, also called nudibranchs!
If we’re going to get scientific about it, the word nudibranch literally means naked gills. Nudi comes from the Latin word meaning naked, while branch comes from the Greek word for gills. These guys extract oxygen from the water just like fish do!
What Nudibranchs Look Like
Nudibranchs can range in size from a teeny tiny four millimeters all the way up to 60 centimeters. They also present an incredible array of shapes and forms.
Some nudibranchs are round and wildly garnished like cookies. Meanwhile, others are more faithful to their ancestors, keeping the slug-shaped body but dressing themselves with bright colours as a warning sign.
There are nudibranchs that have evolved into camouflaging saddle mount shapes. And there are even nudis that have a mane-like set of gills on their backs, called the cerata, that give them Gorgonian looks.
In the nudibranch world, if you can dream it, they comply!
Nudibranchs are marine not-so-distant cousins of terrestrial snails and slugs. They crawl over the sand by utilizing their muscular foot, just like their land counterparts. This muscular foot runs along its body from head to toe.
Only three of the known species of nudibranchs do not move this way. That’s three out of the three thousand scientifically classified ones! These unique nudibranchs are indeed the exceptions, as they are powerful swimmers and live in open waters.
Nudibranchs are even strange beyond their looks. Individual nudibranchs do not have a defined gender, as they are hermaphroditic animals. This means, when they mate, they give and simultaneously receive the elements needed to create a new generation.
After several minutes, the mating finishes. Then, each of the individuals will lay its eggs in due time.
Nudibranch Eggs and Early Life
Again, the size question. Some species of nudis lay a minimal number of eggs –one or two, as is the case for some species. At the same time, others lay eggs by the millions in spiral ribbon-shaped nests. With over three thousand species, nudibranchs cover it all.
Once born, the baby nudibranchs look like the tiniest version of their parents and are ready to begin their crawling life. They will live anywhere from a few weeks for the short-living nudibranchs group to around a year for the longest-living species.
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Evolution has made nudibranchs shell-less in their adult form. Although, in the very first stages of their life, they do have a shell. Snail heritage, am I right?. Most of them lose their shells in the very first stage of the larval phase. While in other cases, they are still unborn in the egg when they lose their shells.
So, without carrying a house on their back, they can show the world the magnificent beauty of their colours, patterns, and shapes. And what extraordinary designs they have.
How Nudibranchs Sense Their Environment
The nudibranchs depend on chemicals throughout its life to get information about their environment. Their most powerful sensing organs are a couple of antenna-like tentacles located in the head area.
They can perceive tastes and smells through this set, an absolute need for food searching. These organs are light and touch-sensitive as well. In some cases, when it feels under threat, the nudibranch completely retracts them. Due to this reaction to threats such as a strobe light, some pictures show un-antennated specimens.
They also have what can be described as elementary eyes in the form of embodied sensors in the head area. However, their “eyes” can only sense if there is light present or not.
Cool Facts About Nudibranchs
When undisturbed, the nudibranchs roam searching for mates or food. They are all carnivorous; there are even recorded cases of nudibranch cannibalism. Nudis are efficient recyclers because their life depends on it!
The ways the nudibranchs use chemicals to protect themselves deserve an entire collection of academic theses. However, to cut a long story short, they can grasp the venomous components of their prey and wrangle them in their own body, which is primarily for storage. It’s believed that the goal is to taste bad to hungry or curious predators who try to eat them.
Nudibranchs Across the Globe
The nudibranchs’ astounding presence is mainly to thank for their popularity with people worldwide. As they live all over the globe –no sea is without its own nudibranchs species- everybody has access to their own local quota of sea slugs.
For the nudihunters of the world, the doors are wide open. And then, of course, there’s the option to travel to discover new species. Or expand the nudihunter experience by capturing them… with a camera, of course!
Nudibranchs are an object of desire not only to the specialized scientists who study them but also to the nudi fans and freaks you will meet at dive shops worldwide. So beware of being around a group of nudi lovers after an incredible dive; they will tell anyone who will listen about the spectacular nudibranchs they’ve seen.
Do You Love Nudibranchs?
In nature, we all should be constantly aware that no creature, big or small, deserves to be neglected. Despite their minuscule size, nudibranchs are here to remind us of that. Just look at how beautiful they are; who wouldn’t love them?
Let us know in the comments which nudibranch in this article is your favorite. And be sure to subscribe to Ocean Pulse for more underwater stories for divers by divers.
About the Author
Òscar Montferrer is a journalist, scuba diver, and underwater photographer whose graphic work aims to raise awareness about the need to preserve aquatic life. You can see more from him on his Instagram @oscarmontferrer
Great article! I really appreciate knowing more about Nudibranchs and the photos are AMAZING!