Bioluminescence emerged in animals 540 million years ago

Bioluminescence, the remarkable ability of organisms to generate light through chemical reactions, originated in marine invertebrates known as octocorals at least 540 million years ago, according to a new study by researchers at the Smithsonian’s National Museum of Natural History. 

These findings significantly predate previous records, which dated the earliest emergence of this luminous trait in animals to about 267 million years ago in ostracods, a type of small marine crustacean.

Evolutionary history of bioluminescence 

This groundbreaking research not only revises the timeline of bioluminescence’s evolutionary history but also opens new pathways to understanding why this ability developed. 

“Nobody quite knows why it first evolved in animals,” said senior author Andrea Quattrini, the museum’s curator of corals. This mystery underscores the complexity and significance of bioluminescence, which has independently evolved at least 94 times across various species and plays crucial roles in behaviors such as camouflage, courtship, communication, and hunting.

Bioluminescent group of corals 

The focus of the study was on octocorals – an ancient and frequently bioluminescent group that includes soft corals, sea fans, and sea pens. Unlike hard corals, octocorals consist of tiny colonial polyps that secrete a soft framework as their habitat. 

These organisms often exhibit bioluminescence when disturbed, although the exact reasons for this trait remain somewhat elusive.

To determine the origins of bioluminescence in octocorals, the researchers, including lead author Danielle DeLeo, a former postdoctoral fellow and museum research associate, analyzed an evolutionary tree of octocorals developed by Quattrini and Catherine McFadden of Harvey Mudd College in 2022.

This tree, constructed using genetic data from 185 octocoral species, provided a detailed map of the evolutionary relationships within this group.

Bioluminescence in the ancestors of current octocorals

By integrating two known-aged octocoral fossils into this group based on their physical features, the team was able to estimate the timeline of evolutionary splits within the octocoral lineage. They then mapped bioluminescent species onto this tree and applied statistical techniques for what is known as ancestral state reconstruction. 

This analysis aimed to infer the likelihood of bioluminescence in the ancestors of current octocorals. “If we know these species of octocorals living today are bioluminescent, we can use statistics to infer whether their ancestors were highly probable to be bioluminescent or not,” Quattrini explained.

The results were striking: bioluminescence likely existed in the common ancestor of all octocorals around 540 million years ago, a significant advancement over the previous record held by bioluminescent ostracods.

This early emergence suggests that bioluminescence has been a key trait contributing to the evolutionary success and long-term survival of octocorals.

Mystery of bioluminescence 

The findings also raise further questions about the specific uses of bioluminescence in octocorals, prompting DeLeo and her colleagues to plan additional research. They are developing a genetic test to determine the presence of luciferase, an enzyme crucial for bioluminescence, in octocorals. 

This tool will help identify which of the over 3,000 living octocoral species still possess this luminescent capability and which have lost it, potentially shedding light on the ecological factors influencing this trait.

Fascinating biological trait 

Beyond its scientific implications, the study provides essential evolutionary context for the conservation and management of octocorals, which are increasingly threatened by climate change and human activities such as fishing, oil and gas extraction, and marine mineral mining.

The research is part of the museum’s Ocean Science Center’s mission to enhance global understanding of oceanic processes and challenges.

As this study, published in the journal Proceedings of the Royal Academy of Sciences, redefines the ancient origins of bioluminescence, while highlighting the need for further exploration into why such a fascinating biological trait evolved and its role in the survival and adaptation of marine organisms over millions of years.

Advantages of bioluminescence in animals

Bioluminescence offers several advantages in the natural world. Predominantly found in marine organisms, though also present in some terrestrial species, this fascinating biological trait serves various ecological roles. 

Luring prey 

For many deep-sea creatures, bioluminescence is crucial for attracting prey. The deep ocean is pitch dark, so any source of light is likely to draw attention. Organisms can use this to lure smaller creatures close enough to capture them.

Defense mechanism 

Moreover, bioluminescence is used for defense. Some species emit light to startle or distract predators, giving them a chance to escape. Others may use bioluminescence to camouflage themselves, blending in with light filtering down from the surface to erase their silhouette and confuse predators from below.

Reproduction 

In addition to predation and defense, bioluminescence plays a role in reproduction. Certain species emit specific light patterns to attract mates, ensuring that they can find one another in the vast and dark depths of the oceans.

Communication

The light can also serve as a form of communication among members of the same species, helping them signal their location, maintain group cohesion, or even warn others of dangers.

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