Iridogorgia

Image: NOAA Photo Library

Oooo... Aaaaah...

Nice to see some fireworks brightening up the abyss!

Image: NOAA Photo Library

Iridogorgia is a genus containing five known species of beautiful corals found in the deep, dark depths of the Pacific and Atlantic oceans.

Their name comes from the Greek iridos or iris. For us, irises are the pretty, colourful parts of the eye, or else a lovely flower. For the Greeks the word meant "rainbow". Later it could refer to pretty much any circle of colour.

Image: NOAA Photo Library

They do look a whole lot like an eye's iris if you catch them at the right angle!

Image: NOAA Office of Ocean Exploration and Research

The other bit, gorgia, is Latin for splendid or showy... gorgeous! And Iridogorgia certainly are that.

They're made up of a long stalk, firmly attached to rock, which spirals round and around as it grows up.

Image: Photo WHOI
Teeny, tiny polyps!

Attached to the stalk are lots and lots of thin branches, almost like a whirly, twirly feather.

Finally, there are the polyps. What would a coral be without its polyps? A dead skeleton, that's what. So a living Iridogorgia has titchy polyps emerging along the length of the branches. Being a kind of octocoral, each polyp is armed with eight tentacles for grabbing tiny specks of food.

Image: NOAA Office of Ocean Exploration and Research

The five species are I. bella ("beauty"), I. splendens ("shine"), I. fontinalis ("lives in a spring or well". I prefer to think of it as "is a spring that lives in a well"), I. pourtalesii (named after a guy called Pourtales)...

Finally, there's the biggest of the lot, I. magnispiralis ("great coil"). And boy is it big! Some have been measured (pdf) at 5.7 metres (18.7 ft) tall with the longest branches reaching 50 cm (1.6 ft) long. Since the branches grow all around from a big spiral, that makes the whole thing over a metre (3.3 ft) across!

Image: NOAA Office of Ocean Exploration and Research, 2015 Hohonu Moana
Iridogorgia magnispiralis

Not only is it the biggest Iridogorgia, it could be the biggest octocoral in all the deep sea. Giants like this are thought to be as much 400 to 500 years old, since they grow so slowly.

They're like fireworks frozen in time for centuries! Which is useful given how slow so many of the deep sea spectators are.