Sea Slugs: The Pirates of the Ocean
Which are the toughest sea creatures of all? It has to be the nudibranchs! These sea slugs are a formidable enemy to jellyfish and sea anemones because, unlike others, they are not deterred by their tentacles and venom. Worse still, the slugs are able to use these toxins to their own advantage.
Sea anemones cannot escape quickly when an enemy approaches. They therefore rely on tentacles covered in stinging cells armed with a toxin. Jellyfish have similar weapons. Their stings are like a small capsule containing a coiled, hollow filament: a tiny poisonous “harpoon”. In response to a stimulus (e.g. a touch), this filament shoots out with great force and pierces the prey. The toxin is then released, which can paralyse or kill the prey.
It’s a powerful defence mechanism, that keeps almost all sea predators away. Almost all, because some nudibranchs are resistant to the toxin.
Dinner first
Nudibranchs or sea slugs, like their counterparts on land, have no shells. Nevertheless their appearance is often very impressive, with vibrant colours ranging from bright purple to vivid blue or fluorescent orange. But do not be deceived by their attractive appearance. Some nudibranchs are fearsome pirates, hunting the jellyfish and anemones that other marine predators avoid and devouring them - stinging cells and all.
How can these sea slugs eat stinging cells without being bothered by them? Granules are released by the cells in the first part of their digestive system, forming a protective layer. This way the sea slug can continue munching on its meal.
Then steal
Since nudibranchs are “homeless”, carrying no protective shelter to use for defence, the molluscs have decided not only to gobble up the stinging cells, but to make good use of them: it stores the little harpoons in special pouches. If it ever finds itself in danger in future, it simply fires the stolen stinging cells as if they were its own weapons all along.