It is said that all global species and their populations are the building blocks of ecosystems, individually and collectively securing the conditions for life. Not just theirs, but ours too. I don’t have the space to name them all, but this one caught my attention.

A bright blue dragon called Glaucus atlanticus

This bright blue assassin and master of disguise is called Glaucus Atlanticus. It is commonly known as the blue dragon and is a sea creature, a type of sea slug known as a nudibranch, and it would be hard to decide if it was a freak of nature or a work of art. They are also known as blue sea slugs, blue angels, or sea swallows, and can be found on the surface of the Atlantic, Pacific and Indian Oceans in temperate and tropical waters throughout the world

Their pretty feathery tendrils are more than just elaborate decoration – they hold a deadly secret. Glaucus atlanticus are foraging predators, and these tendrils, call cerata, hold highly poisonous stinging cells, used for both hunting and self-defence.

They have a connection to Portugal, and although not native to our waters, they have been spotted in Madeira and Porto Santo. Their connection, however, is what they eat, and what they do. While they are not venomous in themselves, they prey on different venomous sea creatures, one of them being the Portuguese Man O’War jellyfish - Physalia Physalis - (which isn’t actually from Portugal at all), and when this little blue dragon munches on this poisonous creature it cunningly keeps the poison, therefore becoming toxic itself.

Small but deadly

This ornate slug rarely grows larger than 3cm long and will float on its back, having swallowed a little air bubble, and will float on the surface of the sea. Weak swimmers, they are at the mercy of the wind and currents. Although floating on the surface leaves them exposed to airborne predators, their back-colour aids as a camouflage against the backdrop of the sea, while their pearly silver/grey underside blends in with the bright sea surface, hiding them from predators below. The technique is known as ‘countershading’ which describes why the blue dragon is darker on its upper side and light on its underside.

Groups of blue dragons float together creating formations known as ‘blue fleets.’ This behaviour makes sense for feeding and mating, but it does create conditions favourable for oceanic winds to blow them ashore, so a ‘blue fleet’ might end up all in the same place.

Blue dragons curl into balls to protect themselves when they're caught in waves and are being pushed toward the beach. And if they do become stranded on the sand, their venom remains active—even after they die. This means that anyone who picks up or steps on these creatures will experience their fiery sting, so despite their beauty, this tiny little animal is deadly. Although a sting isn’t guaranteed, don’t take the chance, as apparently one sting from this little guy can lead to nausea, pain, vomiting, and skin problems that include acute allergic contact dermatitis.

Are these little blue slugs rare?

Though they're infrequently encountered by humans, it's unclear just how rare blue dragons are because they're so tiny and therefore difficult to quantify in the vast, open ocean. The species has not been assessed by the IUCN.

If you thought that garden slugs were bad, be grateful that the blue dragon won’t invade your garden and eat your cabbages!

Author

Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan