Helen - In the mollusk group there are lots of glowing squid and octopus and so on. But in fact for gastropods, the seashells, there is really hardly any bioluminescence except for a little brilliant creature Hinea brasiliana, also known as the clusterwink, which has to be the best name for a creature.
Basically they are called that because they group together in crevices at low tide, these live on the coast of Australia. Apparently once the tide comes in they wake up and scoot around busily, but when the tide comes in they all cluster together, hence the name cluster wink.
It’s a family Planaxidae, when they are just sitting there in the day light they look like little yellow shells, fairly normal yellow shells. But put one in the dark and poke it and it glows bright green. It is basically a kind of burglar alarm, the idea is that is it shouting out for help and essentially saying “help, help I’m being attacked” to attract perhaps other predators of the thing that is attacking them and to basically make themselves look bigger.
A study came out earlier this year that looks into how this happens. They have two blobs of light emitting cells inside their bodies but it comes out like a whole glowing shell, a bit like a light bulb essentially.
Turns out this is caused by the crystalline structure of the shell that is specifically filtering and diffusing the light to amplify it and it does it better than any commercially available material that we use to do similar things. It only works with green light, red and blue just gets stuck they don’t get transmitted through the shell.
It is just really awesome, the researchers are now trying to bio-mimic this structure to try and make things that we can use for ourselves. And they are also looking at other members of the Planaxidae family to work out how this particular fireworks trick evolved.
Find out more:
Deheyn and Wilson (2011).Bioluminescent signals spatially amplified by wavelength-specific diffusion through the shell of a marine snail. Proc. Roy. Soc B.