Bioluminescence, the captivating phenomenon that enables living organisms to emit light, has a far more ancient history than previously believed. Recent research on octocorals reveals that this mesmerizing ability dates back at least 540 million years.
Octocorals, despite their name, are not closely related to corals. They belong to a group of marine invertebrates that inhabit and illuminate Earth’s oceans. A new study published in the Proceedings of the Royal Society B suggests that these creatures have been lighting up the deep sea since the late Precambrian era.
“The evolution of light-detecting animals during the Cambrian period raises the intriguing possibility of light-based interactions between octocorals and other species during a time of rapid animal diversification and niche occupation,” explains Andrea Quattrini, a zoologist at the Smithsonian Institution and the study’s senior author. “Bioluminescence is now recognized as a crucial form of communication for numerous organisms, especially those in the deep sea.”
A vibrant octocoral in its underwater habitat.
The Chemistry of Octocoral Bioluminescence
The bioluminescence in octocorals is facilitated by an enzyme called luciferase, which triggers a light-producing chemical reaction. This process differs from the bioluminescence observed in fireflies, which utilize magnesium and ATP for their intermittent flashes, according to Quattrini. While biofluorescence, relying on external light sources, was recently found to be more widespread in mammals than previously thought, it’s distinct from bioluminescence, where the glow originates from within the organism itself.
Tracing the Evolutionary History of Bioluminescence
Bioluminescence has evolved independently at least 94 times, as indicated by a 2020 study. Previously, the oldest known instance was believed to be in ostracods, small crustaceans. To pinpoint the origin of bioluminescence in octocorals, the research team consulted an evolutionary tree of these animals developed in 2022. By incorporating octocoral fossil data and mapping extant bioluminescent species, they employed ancestral state reconstruction to estimate the age of the animals’ common ancestor. Their analysis pointed to approximately 540 million years ago, just before the Cambrian Explosion, a period of remarkable biological diversification.
An infographic illustrating the evolutionary tree of octocorals.
Future Directions in Bioluminescence Research
Currently, the researchers rely on statistical methods to determine the origin of bioluminescence. However, Quattrini envisions a future where advancements in ancient DNA techniques might allow for the detection of DNA, such as that of luciferase, in ancient fossils. While the oldest DNA discovered to date, from mammoth remains on Wrangel Island, is around 1 million years old, the ancient glowing octocorals predate this by a significant margin. This new understanding of bioluminescence’s deep-time origins provides valuable insights into the evolutionary history of this fascinating trait.
The Significance of Ancient Bioluminescence
The discovery of bioluminescence in octocorals dating back 540 million years has significant implications for understanding the evolution of life in Earth’s oceans. It suggests that light-based communication and interactions may have played a crucial role in the diversification of life during the Cambrian period. Further research may reveal even more about the ecological significance of bioluminescence in ancient marine ecosystems.
Further Reading: Some Paleontologists Think They’ve Found Fossilized Dinosaur DNA. Others Aren’t So Sure
