Nudibranch Superpowers
This piece was originally developed in conjunction with the Nudibranch Night performance for the SALT festival in Port Lincoln.
Nudibranchs can be found in every reach of Earth’s oceans, from the intertidal zones to the pressure-crushing depth of 2500m. In Port Lincoln, we find them under the jetty.
Coming from the class of gastropods, nudibranchs share some features with their cousin, the slug: a boneless body, two ears standing on top of the head (often mistaken as eyes), and a wriggling movement. But unlike the slug, their vibrant colours and bold features result in Pokémon-like creatures one can only assume were designed by children.
Some sport a purple body with orange finger-like projections lining the back, others have the design of the starry night sky complemented by a pair of red horns. All have a pom-pom on their backside, which serves as an external set of gills, earning them their name nudi (naked) branch (gills).
Saint Vincent’s Nudibranch (Hypselodoris saintvincentia) under the Port Lincoln jetty photos taken by citizen scientists from iNaturalist
There are 3,000 species of nudibranchs worldwide, eight of which find a home in Port Lincoln. If you take your snorkel under the jetty, you may see the Lemon Lolly nibbling on jellyfish or slurping up other sea slugs. Or maybe, you’ll see Goniobranchus species (undescribed) giving birth to millions of babies in a ribbon of colour. Less visible, yet equally fascinating, are their superpowers – the unusual and astounding adaptations they’ve evolved to survive.
Goniobranchus species (undescribed) and its egg ribbon under the Port Lincoln jetty – photo @oceanicshelley
You are what you eat
Nudibranchs are conspicuously colourful in an ocean of animals trying to blend in. It may seem a poor choice to adorn oneself so vibrantly, but it’s all part of the plan. Their colour evolved as a warning to predators, saying, “I am poisonous; do not eat me.” Simultaneously, it serves as camouflage to blend in with the colourful coral and anemones they are known to eat.
Unlike stick insects to sticks or greentree frogs to leaves, nudibranchs aren’t born with colours to match their habitat. Nor can they take on their background’s colour in real-time, like chameleons. Instead, they steal colour from what they eat. As a nudibranch munches down on an anemone or a different colourful prey, it keeps the colourful pigments and absorbs them into its flesh. It can then wear these pigments on its skin and take on the colour of its food.
Dendrodoris arborescens under the Port Lincoln jetty photos taken by citizen scientists from iNaturalist
Stealing the sting
Every species on Earth is eaten by another species and sometimes by its own (as is the case for cannibalistic nudibranchs). The common problem of being someone else’s food has created a fantastical array of solutions – and nudibranchs are no exception. From poison to barbs to stinging cells – basically, anything you can think of has arisen in nature to avoid predation. The nudibranch side-stepped the requirement to evolve their own defences by learning to steal the good work of others.
Many nudibranchs feed on animals containing stinging cells, such as jellyfish. Not only are they unaffected by the sting of such animals, but they’ve evolved to capture those stinging cells and translocate them into their body’s extremities. When a predator next spooks the nudibranch it shoots the newly acquired weapon at the animal, stinging them just like a jellyfish.
Lemon Lolly Nudibranch (Doris chrysoderma) under the Port Lincoln jetty. photos taken by citizen scientists from iNaturalist
Plant or animal?
Although not seen in Port Lincoln’s nudibranchs, one last superpower is worth mentioning. Some nudibranchs eat algae, a plant floating on the ocean’s surface, as their primary food source. But, instead of digesting the algae as many animals do, the nudibranch keeps the plant alive in its body. Through the semi-translucent flesh, the trapped algae continues to photosynthesise, creating energy from the sun. Akin to humans keeping cows and drinking their milk, the Nudibranch consumes the energy their algae creates.
Nudibranchs, however, go a step further than we do. When the algae breaks down, chlorophyll(responsible for photosynthesis) is isolated and integrated into the Nudibranch’s cells. Now, the animal can photosynthesise, just like a plant.
Verconia verconis, under the Port Lincoln jetty photos taken by citizen scientists from iNaturalist
Lincoln legends
There is a world of wonder waiting below the ocean’s surface. Should we dive down, we may have the luck of spotting Earth’s very own Pokémon, and if we pay attention for long enough, we may even see them going about their day.
Though truly striking in their appearance, nudibranchs are even more than meets the eye. Their unique ability to absorb “superpowers” from their prey makes these soft-bodied sea slugs a tiny force to be reckoned with. Underneath our very own jetty lives this extraordinary example of nature’s mysterious and wonderful creativity
We acknowledge that the Port Lincoln jetty area is the traditional Country of the Barngarla people. Acknowledging their deep connection with Country and paying respects to elders past, present and emerging.
This resource has been developed by Shannon Evenden as part of ‘SALT on the Water – Night of the Nudibranch’, a feature event of the 2024 SALT Festival across the Southern Eyre Peninsula. All photos were sourced from iNaturalist submissions of Nudibranchs from the Under the Port Lincoln Jetty Project – iNaturalist page. https://www.inaturalist.org/projects/life-under-the-port-lincoln-jetty