Bioluminescence First Evolved in Vertebrates Half a Billion Years Ago; How Did Glowing Sea Creatures Develop This Trait?

Bioluminescence is a phenomenon which occurs across a wide range of both flora and fauna, from jellyfish to firefly, and even fungi. It is also one of the wonders of nature which attracts tourists and researchers alike.

Scientists initially thought that bioluminescence first appeared about 267 million years ago in marine crustaceans called ostracods. However, a new study suggests that this strange ability could be a much older trait.

Evolution of Bioluminescence

In marine animals, the glow they produce through bioluminescence makes the animals look like they are electrical, giving them beautiful colored light. Bioluminescence has independently evolved at least 100 times in animals and other organisms.

Some glowing creatures, like fireflies, use their natural light to communicate in the darkness. Meanwhile, other animals such as anglerfish use this ability to attract prey or to scare away predators.

However, it is not always clear why bioluminescence evolved. This has been the case for octocorals, a diverse subclass of anthozoan cnidarians possessing polyps with eightfold radial symmetry.

Octocorals can be located in both the deep ocean and shallow water. They produce an enzyme called luciferase to break down a chemical that makes light. But whether these glowing soft-bodied organisms use their light to attract zooplankton as prey or for some other purpose remains unclear.

Experts assume that bioluminescence was an ancient trait, but they did not expect that the ancestors of all octocorals were also bioluminescent. It is also a mystery why the trait first evolved in animals. However, scientists do know that this trait can help animals in communication, hunting, courtship, and camouflage.

First Glowing Animals

To find answers to this mystery, the researchers traced the lineage of octocorals and the story behind their evolution. This group of organisms only glow when they are disturbed by an external force or when they are bumped in some way. This has always posed a mystery as the real reason for their bioluminescent ability remains unclear.

Led by museum research associate Danielle DeLeo, the research team used two fossils to map when octocorals split from other ancestors and adapted bioluminescence. Using different statistical methods, they discovered that these organisms were bioluminescent 540 million years ago, about 273 million years before ostracods developed the ability.

Some species with the ability to detect light evolved during a similar time during the Cambrian period. Thus, the research hints at the possibility that interactions involving light happened between organisms during a time when animals were diversifying rapidly and occupying new niches. The fact that bioluminescence has been maintained for so long also suggests that it must have significantly contributed to the overall fitness of the animals.

The study presents the oldest published record for the appearance of bioluminescence on Earth and more than doubles the previous timeline for when this phenomenon first occurred. According to the researchers, their findings support the idea that light signaling is one of the earliest forms of communication on our planet.

From these findings, researchers are trying to look into which octocorals still have bioluminescence and which do not. This may take a while since there are more than 3,000 species of octocorals. Still, the result of their study will help inform them further of the strange evolutionary trait and why it came to be. Additionally, the study also provides more context into the evolution of these marine creatures.