The Blue Angel: Glaucus Atlanticus

On December 5, 2014 by Tim Newman

Glaucus atlanticus - sea swallow

Glaucus atlanticus, variously known as the sea swallow, blue angel, blue glaucus, blue dragon, blue sea slug and blue ocean slug, is a quite wonderful looking chap. These winged neon tubes are part of the sea slug family, but don’t be fooled, their ethereal look belies their power.

The blue sea slug was named after one of the Greek gods of the sea – Glaucus – who was turned into a kind of merman after eating a magical herb. They’re mostly found off the East and South Coast of South Africa, warmer European waters, the east coast of Australia and Mozambique.

Despite only stretching to a meager 3 cm in length, the blue angel dines upon one of the most feared creatures in the ocean – the Portuguese man o’war, who can stretch up to 30 feet in length. The fearsome man o’war looks like a jellyfish but it is in fact a siphonophore. Rather than being a single organism, siphonophores are comprised of a huge society of smaller organisms, all with specialised roles within the physiology of the blob.

Glaucus atlanticus - gastropods

The Portuguese man o’war is armed with stinging nematocysts which wound as many as 10,000 people per year, mostly off of Australia’s eastern coast. The kick that these nematocysts provide to humans is incredibly uncomfortable at best and fatal at worst.

Despite the powerful venom that these wobbly demons kick out, the blue angel is unphased. It also dines on relatives of the Portuguese man o’war, like the “by-the-wind-sailor” (Velella velella), and the blue button (Porpita porpita). However, apparently it prefers the taste of the Portuguese man o’war.

Glaucus atlanticus - eating Man o'War

The blue angel is one of the very few sea creatures which can attack and consume the man o’war with impunity (another is the blanket octopus). This ability is interesting enough, but it gets better.

Stealing Weapons

What makes the blue angel really strange is that they manage to collect the man o’ war’s venomous nematocysts and store them in the tips of their feathery wings.

Blue angels effectively steal the man o’war’s weapons and use them for their own protection. Thanks to this ability, humans can get a nasty sting from the blue angel if handled.

In fact, the sting can often be worse than the man o’war’s because of the way in which the blue angel chooses its weapons. Rather than picking nematocysts randomly, the blue angel manages to select just the most venomous nematocysts, he is also able to condense the venom.

Glaucus atlanticus - blue sea slug

The Blue Angel’s Paintjob

The blue angel spends much of its time floating upside down at the surface of the water, passively being shunted around by the waves. This position, belly up to the sun, is possibly one of the reasons for its impressive colouring. The shock of blue might help deflect harmful UV rays from the sun.

The UV theory may or may not hold water, but the blue slug’s countershading probably acts as a dandy kind of camouflage. It lies with its blue bits pointing up, camouflaging it against the sea and protecting it from aerial attacks; and the greyish side it points down, making it tricky to see from below the waves.

So, despite looking like a cartoon representation of a Martian fish, this thing is actually pretty monstrous. They’re still mighty fine to look at from afar though.

Glaucus As A Pet

There seems to be a fair bit of interest in keeping these guys as pets, but, as far as I can tell, not too many people bother. After all, they’re tiny, they hardly move about and if you touched it you might have to go to hospital.

Although, having said that, if the little guys could be coerced into eating things that aren’t poisonous, then I imagine they would lose their sting. So, go for it if you fancy it.

VIDEO: Glaucus Atlanticus Feeding On Man O’War



Here’s some more pics:

Glaucus atlanticus - blue sea slug nematocysts Glaucus atlanticus - blue dragon

Glaucus atlanticus - blue sea slug 2 Glaucus atlanticus - blue sea slug 3 Glaucus atlanticus - blue sea slug lunch






@media all and (max-width: 228px) { div#darkbackground, div.visiblebox { display: none; } }