Bioluminescence emerged in animals at least 540 million years ago among a group of marine invertebrates known as octocols, according to a new study by scientists at the Smithsonian National Museum of Natural History.
The results were published on: Proceedings of the Royal Society BThis could push back the previous record for the earliest appearance of light in an animal by about 300 million years and could someday help scientists unravel why the ability to produce light emerged in the early years. place.
Bioluminescence, the ability of living things to produce light through chemical reactions, has evolved independently in nature at least 94 times and is involved in a wide range of behaviors, including camouflage, courtship, communication and hunting. Until now, the earliest origins of bioluminescence in animals were thought to be in small marine crustaceans called ostracods, about 267 million years ago.
But the origins of bioluminescence as a literally illuminating property have been overshadowed.
“No one knows for sure why this first appeared in animals,” said Andrea Quattrini, the museum’s coral curator and senior author of the study.
But before Quattrini and lead author Daniel DeLeo, a museum research assistant and former postdoctoral researcher, could finally address the broader question of why bioluminescence occurs, they needed to know when this ability first emerged in animals.
Research methodology and results
Wanting to investigate the earliest origins of this trait, the researchers decided to look at the evolutionary history of octocorals, an evolutionarily ancient and often bioluminescent group of animals that includes soft corals, sea fans and sea pens. Like hard corals, octocols are tiny colonial polyps that secrete a framework for shelter, but unlike their stony relatives, this structure is generally soft. Glow-in-the-dark octagons generally only glow when bumped or otherwise disturbed, and the exact function of their light-emitting ability remains somewhat mysterious.
“We wanted to find the timing of bioluminescence, and octocorals are one of the oldest groups of animals on the planet known to be capable of bioluminescence,” DeLeo said. said. “So the real question was: When did they develop this ability?”
It is no coincidence that Quattrini and Catherine McFadden of Harvey Mudd College completed a highly detailed, well-attested evolutionary tree of octagons in 2022. Quattrini and colleagues created this map of evolutionary relationships, or phylogeny, using genetic data from 185 octocol species.
Using this evolutionary tree based on genetic evidence, DeLeo and Quattrini placed two octopus fossils of known age into the tree according to their physical characteristics. Using the age of the fossils and their relative positions in the octocol evolutionary tree, scientists today were able to roughly infer when the octocol lineage split into two or more branches. The team then mapped the branches of the phylogeny containing living bioluminescent species.
After dating the evolutionary tree and labeling the branches containing the glowing species, the team used a series of statistical techniques to perform an analysis called ancestral state reconstruction.
“If we know that these octocoral species living today are bioluminescent, we can use statistical data to infer whether their ancestors were likely to be bioluminescent,” Quattrini said. “As the number of species that share a trait increases, the probability that those ancestors also had that trait increases as we go back in time.”
Researchers used many different statistical methods to reconstruct the ancestral state, but they all came to the same conclusion: About 540 million years ago, the common ancestor of all octagons was likely bioluminescent. This is 273 million years before the glowing shell ostracods, which previously held the title of earliest evolution of bioluminescence in animals.
The thousands of living species of octagons and the relatively high frequency of bioluminescence suggest that this feature played a role in the group’s evolutionary success, DeLeo and Quattrini said. While this further raises the question of what exactly octocols use bioluminescence for, researchers say the fact that it’s persisted for so long underscores how important this form of communication has become for their health and survival.
Future directions for research and conservation
Now that the researchers know that the common ancestor of all octagons was probably already capable of producing its own light, they want to take a closer look at which of the more than 3,000 living species in the group can still glow and which have lost their light. talent. This may help focus on a set of environmental conditions that are associated with bioluminescence capacity, potentially illuminating its function.
To that end, DeLeo said he and some of his co-authors are working on a genetic test to determine whether octocoral species have functional copies of the genes underlying luciferase, an enzyme involved in bioluminescence. For species of unknown brightness, such a test would allow researchers to arrive at an answer one way or another more quickly and easily.
In addition to shedding light on the origins of bioluminescence, this study also provides evolutionary context and information that can inform monitoring and management of these corals today. Octocorals are threatened by climate change and resource extraction activities, including fishing, oil and gas extraction and leaks, and more recently marine mining.
This research supports the Museum’s Ocean Science Center, which aims to disseminate and share ocean knowledge with the world. DeLeo and Quattrini said there is still much to learn before scientists understand why the ability to produce light first emerged, and while they place the origins of their results deep in evolutionary time, it is possible that future research may reveal that bioluminescence is much older.
Source: Port Altele
