Do you think they glow just for the sake of beauty? They are just "talking"!

Feng Weimin

Bioluminescence is a fascinating phenomenon, but its origins have always been obscure. A new study published in the Proceedings of the Royal Society B recently revealed this mystery. Scientists from the Smithsonian National Museum of Natural History in the United States pointed out that bioluminescence can be traced back to at least 540 million years ago, when the marine invertebrate octocorals had evolved this ability.

Luminescence comes from luciferase in the body

Octocorals are marine invertebrates and one of the oldest known groups of bioluminescent animals. They have an enzyme called luciferase, which catalyzes a chemical reaction that produces light.

There are many species of luminescent octocorals, including soft corals, sea fans, and sea pens. Like hard corals, octocorals are also tiny colonies of coral polyps that usually glow when they are hit or otherwise disturbed. Studies have shown that the more luminescent species there are in living octocorals, the more likely it is that their ancestors had this trait.

However, the oldest known example of bioluminescence has long been believed to come from a small marine crustacean called an ostracod that lit up its body 267 million years ago.

To this end, scientists studied the genetic data of nearly 200 species of octocorals and produced a detailed evolutionary tree of octocorals. In this study, scientists also added octocoral fossils of different ages and known ages to the evolutionary tree to better illustrate the relationship between species. They also drew a phylogenetic branch characterized by living octocoral species with bioluminescent properties. Afterwards, scientists conducted a variety of statistical analyses to reconstruct the ancestral state of octocorals. The final result is: about 540 million years ago, the common ancestor of all octocorals was likely a bioluminescent body. This is 273 million years earlier than the crustaceans previously known as the earliest bioluminescent.

Luminescence may be the "language" between organisms

Scientists have found that bioluminescence may have first emerged in the dark deep sea, almost at the same time as complex animals. The fact that the bioluminescence characteristics of octocorals have been preserved for hundreds of millions of years suggests that this characteristic may have given the species some kind of evolutionary advantage.

In fact, bioluminescence is a survival choice. Taking the octopus as an example, when scientists observed the cross section of its light-emitting organ through a microscope, they found the remnants of the unique muscle ring of the sucker, which is the sucker that has evolved into a light-emitting organ. Therefore, the octopus uses the luminous sucker to attract mates and food, and then ends its benthic life and survives in a more open ocean. The sucker originally used to cling to rocks and shellfish loses its function and gradually degenerates, but the mutation in this part is selected to remain, which is the principle of the evolution of the sucker into a light-emitting organ.

Light is a "language" used for communication. In simple terms, bioluminescence and general light signals may be one of the oldest ways of communication between organisms. Therefore, the "language of light" has been inherited in evolution as a means of survival.

In addition, light is also a kind of energy, and the survival strategies of organisms have one basic commonality: to save energy to the maximum extent possible while maintaining normal life activities. Therefore, active luminescence must be an important part of the survival of luminous organisms.

Bioluminescence has a long history. Hundreds of millions of years of evolution have enabled more and more organisms to have the ability to luminesce. This phenomenon can not only help various organisms gain the upper hand and advantage in the competition for survival, but also greatly benefit humans. It is now widely used in engineering, chemistry, medicine, agriculture and other fields.

(The author is a researcher at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, and the honorary curator of the Nanjing Paleontological Museum)