Thousands of feet below the sea’s surface, it is incredibly dark. Food is scare and whatever is available needs to be approached carefully – or lured carefully – lest it should flit away again. A jellyfish quietly glides through those black waters, suddenly sensing movement and potential prey. Quickly it lights up, emitting a fluorescent glow.
Beautiful light display:
Little fish, curious of this sudden light source, swim by to take a closer look. And closer, and closer until they get stuck in the jellyfish’s tentacles. The light show ends as quickly as it started and the jellyfish proceeds to devour its prey. Cruel? Survival, 1.5 miles beneath the sea.
Though quite brilliant (pardon the pun), bioluminescence is not rare – about 90% of all ocean animals are bioluminescent. The feature is not only used to attract prey, but has three other important functions: camouflage; its opposite, a warning message to potential predators; and communication with members of the same species, for example when mating. It’s like flashing your best, er, tentacle forward.
Glowing red, deep down:
Touch for the jellyfish is a big no-no, a warning sign: Upon touch, jellyfish will light up, warning predators to stop doing what they’re doing and exposing them at the same time to their potential predators.
Who’s bothering whom? Two longfin bannerfish nibbling on a jellyfish:
Jellyfish produce bioluminescence through a reaction of the two chemicals luciferin and luciferinase. When triggered (e.g. through touch), luciferin gets oxidized by luciferinase. Their reaction results in a photoprotein that causes the bluish glow. Some jellyfish have an additional protein, the green fluorescent protein (GFP), which converts the blue light to green. A recently discovered and yet unnamed Cnidarian in the genus Erenna even emits fluorescent red. Bring on the light show!