The first glow-in-the-dark animals may have been ancient corals deep in the ocean

Many animals can glow in the dark. Fireflies famously blink on summer evenings. But most animals that light up are found in the depths of the ocean.

In a new study, scientists report that deep-sea corals that lived 540 million years ago may have been the first animals to glow, far earlier than previously thought.

“Light signaling is one of the earliest forms of communication that we know of — it’s very important in deep waters,” said Andrea Quattrini, a co-author of the study published Tuesday in the journal Proceedings of the Royal Society B.

Today, marine creatures that glimmer include some fish, squid, octopuses, jellyfish, even sharks — all the result of chemical reactions.

Some use light to startle predators, “like a burglar alarm,” and others use it to lure prey, as anglerfish do, said Quattrini, who is curator of corals at the Smithsonian National Museum of Natural History.

Still other animals use light as a beacon to find mates.