A stunning siphonophore recently floated past one of the cameras operated by the Nautilus Live expedition, which is a project that aims to explore the creatures of the deep in the Gulf of Mexico and Caribbean Sea.
A siphonophore is a close relative of the jellyfish, but rather than being a single organism, it’s actually a whole colony of tiny organisms called zooids working together to survive. The deadly Portuguese man o’ war is perhaps the most famous example of a siphonophore, thanks to the 10,000 or so stings it inflicts on Australians every year during the summer months.
But what’s particularly special about the siphonophore in the video above is its colour, says R.R. Helm from Deep Sea News:
What’s amazing to me about about this animal is not just its strange shape, but its colour. I’ve seen red siphonophores like this, a couple orange, but never ever this strange purple-blue. It’s a shocking shade, and it makes me wonder what on earth a colour like that is doing down so deep.
Many deep-sea animals are red. Because there is no red light in the deep sea, very few animals can see red pigment (unless they make their own red light). In the deep sea, red looks like pitch black. But what about purple? Is there any benefit to being purple? Or is this just a side effect of something it eats or where it lives?
Fortunately the Internet came through for us in the form of Steven Haddock, an expert in bioluminescence and zooplankton at the Monterey Bay Aquarium Research Institute in the US, who offers Deep Sea News a pretty great explanation. Haddock says he’s seen enough of these creatures eating dark-coloured fish to make him suspect that they're indeed developing their own colouring from the purplish-black prey they consume.