Black Long-spined Sea Urchin

Image: Patrick Randall

It's the water hedgehog...

OF DOOM!

Image: Patrick Randall

And by water hedgehog I of course mean Sea Urchin.

And by OF DOOM I mean, er, OF DOOM, actually.

Image: Liam O'Brien
It's just a void! A jagged void... OF DOOM

Black Long-spined Sea Urchins are creatures of nightmare. It's as if someone said, "What would pure, unadulterated pain look like if it crawled out of your brain and enjoyed a bizarre, physical life of its own?"

No wonder they look like something that could kill the Super Mario Brothers with a single touch!

Image: Sean Nash

There are eight species of Black Long-spined Sea Urchins, all belonging to the genus Diadema. Most of them are black and have long spines, so that makes sense. But Diadema?

A diadem is a kind of jewelled headband worn by monarchs, royals and other fancy-schmancy types. It's a tiara, basically, except macho men can wear it, too. But who would want to put a Long-spined Sea Urchin on their head? Surely it can only be the Dark Statue of Liberty OF DOOM, Goddess of the Black Sun. Well, it's there when she wants it.

Image: rmooi

Diadema Sea Urchins are not just Long-spined, they're the Longest-spined of all Sea Urchins. Their actual body is usually just 10 cm (4 in) across but the spines can be up to 30 cm (a foot) long! They're also very sharp and, if you get past the really long primary spines, you'll come up against the shorter secondary spines. Those ones are venomous. They're not lethal to humans, but they certainly bring the pain.

The fact that these Sea Urchins hurt shouldn't come as a surprise to anyone. Sure, they lack the bright colours and hissing threat displays we usually associate with venomous creatures, but they look like a sinister, three dimensional shadow. Which is somehow worse. The monster isn't in the dark. The monster is the dark.

Image: GRID Arendal
Huddling together for comfort. Because that works, somehow

They're also sensitive to light, so if you get close enough to cast your shadow over them they'll point their spines at you like a tiny army of spear carriers.

It seems to work out very well for them. There may be just eight species, but they're found in shallow, tropical waters all the world. Some of them are common throughout the Indo-Pacific, others are found in West Africa, and they can also be found in both the Pacific and Atlantic coasts of the Americas.

Video: Pei Yan Heng

Diadema Sea Urchins are nocturnal, spending the day hidden in crevices among rocks and coral. They try to, anyway. It's not easy to hide when you're covered in foot long spikes. They mostly eat algae which the scrape off of rocks but they can also eat detritus and the like if they need to.

Long-spined Sea Urchins aren't always black. Youngsters often have stripy spines and there are many of individuals who might be purple, grey or even white.

Image: Simon Coppard

Then there are species like D. mexicanum, who tend to have a touch of the blues...

Image: Enrique Dans

Or D. antillarum, who sometimes has a tinge of red...

And then there's that tearaway rebel, D. palmeri, who is a vibrant red.

Image: Richard Ling

But even the most pitch black of Diademas aren't entirely black. Take a look at them from above and you'll see a strange and rather beautiful pattern of blue lines or white spots. It looks like the after effects of some kind of experiment with Tesla coils.

It's a bit suspicious. If anyone really did manage to provide pain itself a disembodied, physical existence of its own, you know that Tesla coils would be involved.

Image: Massimiliano Finzi

In species like D. savignyi it forms a pattern which looks downright alchemical. This too is suspicious.

You don't get bright blues like that from mere patches of colour. They're actually iridophores, which are crystalline plates that reflect light at particular wavelengths to give off that iridescent effect. They're practically jewels! This, perhaps, is the diadem from which they get their scientific name.

Image: Quartl

And if that pattern of light really is the diadem then the centrepiece must surely be that mysterious sphere which adorns its centre. What is it, I wonder?

Despite appearances, it's not an eyeball. Thank goodness! Maybe it's a symbolic eyeball, signifying the wisdom of the ruler?

Image: Chaloklum Diving

Maybe it's a symbolic pot, suggesting the cornucopia that will bless the wearer's reign?

Maybe it's just a tiny pot that gets packed full of incense so the monarch can smell nice during those all-important royal functions?

Video: nqnnl08

No. It's called the anal papilla.

Yup. It's the anus. I guess even creatures of nightmare need to use the bathroom.