From glowing corals to spitting shrimp, animals have been using bioluminescence to speak for thousands and thousands of years – here's what scientists still don't find out about it

People have long been fascinated by organisms that may produce light. Aristotle, who was each a scientist and a philosopher, wrote the primary detailed Descriptions of what he called “cold light”” greater than 2,000 years ago. More recently, pioneering researchers resembling World War II Army veteran Emmett Chappelle and deep sea submersible pilot Edith Widder research into this phenomenon using novel technologies.

At least 94 living organisms produce their very own light through a chemical response of their body – a capability called bioluminescence. Examples are glowing firefliesAlgae that “glow at midnight bayssmall crustaceans with complicated courtship ritualsdeep-sea fish and corals. But despite its widespread occurrence, scientists still have no idea when and where it first appeared or what its original function was.

As Marine biologists WHO specialize in deep sea habitatsWe know that bioluminescence is especially common within the oceanThis suggests that light production organisms from everywhere in the world tree of Life a fitness advantage that improves their possibilities of survival.

Our research focuses are Octocorals – soft corals resembling gorgonians, which have tree-like shapes and are present in various places on the planet's oceans. They are a various and old group of animals These include about 3,500 species, lots of that are bioluminescent.

Octocorals can form coral gardens and animal forests within the oceans, especially within the deep sea. These communities provide homes and nursery habitats for a lot of other animals, including fish and sharks.

All octocorals use the identical chemical response for bioluminescenceA 2022 study found evolutionary relationships between these coralsThese genetic links and the proven fact that fossils of octocorals exist make these animals a really perfect goal for studying the occurrence of bioluminescence and its distribution throughout geological time.

Tests on bioluminescence within the sea

Over a decade ago, we began testing the flexibility of varied octocoral species to supply bioluminescence. To produce the glowing light, corals should be stimulated either physically or chemically.

Bioluminescence first aroused our curiosity during a research cruise in 2014 on the R/V Celtic Explorer across the Whittard Gorge off the southwest coast of Ireland. We took a tissue sample from a bamboo coral that was recovered from the deep seabed using a remotely operated vehicle.

The vehicle was equipped with grippers that allowed the pilot to gather coral samples and place them in sample containers to maintain the organisms alive and guarded upon surfacing. After this sample got here aboard the vessel, we used forceps to remove a single coral polyp in a dimly lit room and saw a flash of blue light.

Since then, now we have been working with partners from the Monterey Bay Aquarium Research Institute And Tohoku University to record which species can glow, either on the ship after collection or while observing them with low-light cameras on the seafloor. Combined with previously published records, we now know that bioluminescence occurs in around 60 coral species. There are probably many more waiting to be discovered.

When and why bioluminescence emerged

In a study published in April 2024, we presented the oldest record in geological time for bioluminescence on Earth. We have shown that this chemical response evolved several millennia sooner than previously thought, across the time when life on Earth developed over 540 million years ago in a period called the Cambrian ExplosionWe determined this by mapping the presence of bioluminescence onto the octocoral tree of life, a graphical tool biologists use to depict the evolutionary relationships between species.

Bioluminescence can have originally evolved to free radicals – chemically unstable atoms that may damage cells. At some point, nonetheless, it developed right into a type of communication.

Our results show that light signals were the earliest type of communication within the oceans, and we all know that some animals that would perceive light developed through the CambrianOur research shows that light interactions between species occurred at a time when animals were rapidly diversifying and occupying recent habitats.

Gaining and losing light

We proceed to check corals for his or her bioluminescent abilities in various ways. A serious component answerable for light production in corals and other animals is an enzyme called luciferaseUsing DNA sequence data, we’re developing a test for genetic potential for bioluminescence that can make it easier and fewer invasive for us to check this trait.

We have initial evidence that non-bioluminescent octocorals are still homologous luciferase genes – genetic instructions passed down from a typical ancestor of all octocorals. Why corals, which cannot produce light, have retained these genes is a mystery.

Do they produce very faint light that scientists cannot detect with current methods? Or are their luciferase genes nonfunctional? Further studies may reveal why certain octocorals appear to have lost the flexibility to bioluminesce and the way this loss can have affected their survival in several habitats.

Our recent results show that many corals that live in shallow waters but are Deep-sea ancestors retain the flexibility to bioluminesce. It is feasible that some corals have lost this ability over time because it became less useful in shallower ocean areas with more light.

We are also studying how bioluminescence has evolved in other creatures, including shrimps, which rise from deep waters to forage through the day and return to deep waters at night. These animals are exposed to changing light conditions and produce light in diverse, unique possibilities.

A notable example are some shrimp Vomiting of light-producing chemicalsthat secrete glowing saliva to ward off predators. They even have external bioluminescent organs along their bodies that produce blue light.

Studying such organisms improves our understanding of how different amounts of sunshine within the environment, including light produced by organisms, affect the event of bioluminescence and affect the vision of organismsThis may make clear how bioluminescence affected the evolution of the attention and vision as life on Earth diversified about 540 million years ago.

The proven fact that corals have been capable of produce light for a whole lot of thousands and thousands of years suggests that this ability has been essential to their survival. Furthermore, our results support the concept that bioluminescence has been a vital type of communication for a lot of animal species throughout Earth's history, particularly within the deep sea.

This research has given us recent ideas about early animal evolution and communication. Light signals gave animals a brand new approach to communicate in a rapidly changing time when recent predators and a more complex landscape were emerging. Enhanced sensory capabilities within the ocean can have been useful under these conditions. Perhaps bioluminescence is a missing piece of the puzzle that has not been adequately considered in studies of the origin and evolution of prehistoric animals.