Among the bright corals and flashy fish of the earth’s coral reefs live a colorful group of sea slugs called nudibranchs. The name ‘nudibranch’ directly translates to naked gill, which refers to the gills and horns that grow along their bodies. Nudibranchs are a type of mollusk, the same phylum as octopuses and clams. However, unlike clams, these mollusks shed their shells at a young age and become soft-bodied like their octopus cousins.
Over 3,000 individual species (within four different suborders) of nudibranchs can be found all over the world, and most live in shallow, tropical seas. These habitats are one of the major causes of the nudibranch’s impressive coloration. Since their colors are influenced by what they eat, the bright coral, sponges, anemones, and fish eggs found in tropical reefs provide a wide range of prey for these tiny carnivores. While their colors may seem like an easy way for predators to spot them, they often help provide camouflage among the coral and anemones that they live with. On top of their bright hues, some species of nudibranchs can even take on some of the protective characteristics of their prey. For example, the cells that cause a jellyfish or sea anemone’s sting don’t get digested, but instead, get used by the nudibranch for its own defense.
Belanger, J. (n.d.). The Spanish Shawl Nudibranch [Photograph]. Natural History Museum. https://www.nhm.ac.uk/discover/nudibranchs-psychedelic-thieves-of-the-sea.html
When they hunt, nudibranchs use the oral tentacles—the rhinophores—found on their heads to scope out prey, and small, curved teeth to pick up food off of the ocean floor. Since they don’t have true eyes, nudibranchs rely on their rhinophores to help them interact with the world. They can detect light and chemical signals with these small protrusions.
Roberts, F. (2020). Hypselodoris obscura found at Rotunda [Photograph].The Happy Nudibranch. https://thehappynudibranch.com/info/
Chemical communication is another important component of nudibranch daily life. Through the trails of slime left by the animals, they can “talk” to other nudibranchs and deter predators. They leave these trails as they travel, so other nudibranchs can find them easily yet they always have a defense mechanism.
Though these small slugs are a lesser-known species, they are a colorful (and incredibly well-adapted) spot in our big, blue oceans.
About the Author
Oliver Ewy is a Senior in high school with an interest in science, specifically in biology and medical-related sciences. He hopes that his articles will help others find an interest in the natural world and encourage them to pursue scientific careers.
Sources
Feltes, A. (2021, July 11). Nudibranchs. Catalina Island Marine Institute. https://cimi.org/blog/nudibranchs/
How do nudibranchs find each other in the big wide open ocean? (2022, January 15). Ocean Dimensions. Retrieved November 7, 2022, from https://www.oceandimensions.com/how-do-nudibranchs-find-each-other-in-the-big-wide-open-ocean/
Nudibranchs. (n.d.). National Geographic. Retrieved November 5, 2022, from https://www.nationalgeographic.com/animals/invertebrates/facts/nudibranchs-1
Osterloff, E. (n.d.). Nudibranchs: psychedelic thieves of the sea. Natural History Museum. https://www.nhm.ac.uk/discover/nudibranchs-psychedelic-thieves-of-the-sea.html
Silen, A. (n.d.). Nudibranch. National Geographic Kids. https://kids.nationalgeographic.com/animals/invertebrates/facts/nudibranch#:~:text=IN%20THE%20MOOD%20FOR%20FOOD,habitat%20in%20search%20of%20snacks
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