Sound of silence

We can't hear a vanishing species, but they are capable of sound

The vibrancy of coral extends beyond what we can see on the surface.

coral reef
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If you’ve ever owned a home aquarium, there’s a good chance you’re familiar with the colorful Cyphastrea. Some of the most popular Cyphastrea resemble underwater meteor showers, with craters of orange dotting vividly blue bodies.

But it turns out this bizarre-looking marine invertebrate keeping your goldfish company is more than beautiful. According to new research, its DNA is seemingly key to finally understanding coral communication: Despite coral’s silent appearance, researchers found genes in Cyphastrea related to the reception and emission of sound.

This new finding could be used to save quickly vanishing coral reefs. It was presented Tuesday at the 2021 Experimental Biology meeting.

Different examples of Cyphastrea.

Wikimedia Commons

What’s new — In a new report presented at the meeting, the study team identified certain genes related to the reception and transmission of sound in Cyphastrea. But these findings, the study team hypothesizes, apply to all coral species.

Lead researcher Camila Rimoldi Ibanez, a high school student in the dual enrollment program at South Florida State College, conducted the research under the guidance of her mentor, James Hawker, the dean of arts and sciences at South Florida State College

“I was happily surprised to see the presence of these genes in the coral DNA,” Ibanez tells Inverse.

The two primary genes found in the coral — TRPV and FOLH-1 — have previously been observed in sea anemones and freshwater polyps. These two organisms are fairly similar to corals in their biological makeup.

Ibanez also studied two other genes related to the transmission of sound in other animals — OTOF and WAKL2 — but did not find these genes in coral.

Can coral communicate?

Creatures across the animal kingdom interact with sound in different ways. Narwhals and bats, for example, use a sonar process called echolocation to find food, navigate, and communicate. A cricket’s “chirp,” meanwhile, is caused by the vibration that happens when a male cricket rubs its wings together (though an evolutionarily driven mutation is causing some male crickets to lose this ability).

While hearing loss in people can be caused by different factors, for some, it’s driven by a mutation in the GJB2 gene. Meanwhile, previous research suggests TRPV receptors are also essential for hearing in the common fruit fly.

Coral communication, however, has been more of a mystery. It’s known coral can chemically communicate with the algae that live inside their bodies. It’s less known if they can communicate with each other.

One hint is that coral larvae can detect and move toward sound during their development. This study takes what we know a big step forward, providing a genetic basis for coral communication.

Coral bleaching occurs when coral turns white due to heat stress — largely from global warming. Global warming threatens the vitality of coral reefs.


How they did it — Ibanez developed primers for the four coral genes in her research. Primers are short sequences of nucleic acid, which contain chains of complex molecules. These sequences are necessary for DNA synthesis.

Ibanez then amplified the primers with DNA extracted from the Cyphastrea coral. Her scientific method: a common technique known as polymerase chain reaction (PCR) analysis.

In PCR, scientists amplify specific strands of DNA, allowing them to generate multiple copies of the DNA for use in their research.

Finally, Ibanez deployed certain types of gels, known as agarose, to confirm the presence of the TRPV and FOLH-1 genes in coral.

Using these techniques, Ibanez discovered that TRPV and FOLH-1 — which were previously found in similar animals — were also present in coral.

Why are coral important?

Recent studies indicate that as global greenhouse gas emissions rise, marine heatwaves cause coral to “bleach” or turn white, indicating the organism’s death.

Coral rely on algae and other single-celled organisms known as dinoflagellates to keep them fed. The algae live within the coral and the coral feed on their photosynthesis by-products.

These tiny, single-celled organisms are extremely vulnerable to heat. When marine temperatures rise, the algae produce toxins, causing the coral to expel the single-celled organisms. The end result: coral bleaching.

But seemingly healthy coral might actually be hurting, too. As coral become stressed due to global warming, they turn brighter in color, becoming fluorescent instead of their more normal, subdued hues.

Coral reefs, like the Great Barrier Reef, are essential to preserving biodiversity in marine ecosystems. They provide shelter to many sea creatures and protect coastlines from erosion.

They’re also important for humans, too, employing more than half a billion people, according to the National Oceanic and Atmospheric Administration.


Coral reefs, like the Great Barrier Reef, are essential to preserving biodiversity in marine ecosystems. They provide shelter to many sea creatures and protect coastlines from erosion.

They’re also important for humans, too, employing more than half a billion people, according to the National Oceanic and Atmospheric Administration.

Why the new research matters — Ibanez likens the importance of coral’s sound transmission to the way individual plants communicate in a forest. “Different studies are identifying and showing how critical communication between plants is for the livelihood of an entire forest,” she says.

Scientists have been looking for ways to save the coral beyond calling for individuals to reduce their own contributions to greenhouse gas emissions and ocean pollution. Considering Ibanez’s findings, it’s possible a better understanding of coral communication could also help.

“In the same way that the studies are identifying and finding new ways to help forests, if research continues about corals and the importance of sounds in their environment, we might be able to do the same and help our coral reefs through restoration and conservation,” Ibanez says.

A human scuba diver swims near coral. Human noise pollution has impacted other marine creatures. Now that we know coral communicate through sound, we can be better positioned to study the impacts of noise pollution on coral, too.


What’s next — Scientists may have identified these exciting genes, but we’re still fumbling around in the dark when it comes to figuring out just what makes coral communication tick.

“On the bigger scale, I think that research has to be done to be able to answer how, why, and what corals are communicating through sound,” Ibanez says.

Her team has some ideas for future research, which mainly involve digging deeper into the secrets hidden within the endangered animal’s DNA.

“As for right now, the next step in this project would be to sequence the faint bands to have further evidence of sound emission [or] reception genes in the coral DNA,” she says.

With further research, we just might be able to save these endangered invertebrates, preserving marine ecosystems for generations to come.

Abstract: Corals play a huge role in our oceans by supporting the critical coral reefs and contributing with Earth’s ecosystem. Communication is vital for all organisms to grow and exchange information no matter the organization level of the organism. Communication among corals if enhanced and understood could contribute for future leading restoration programs.There are a growing number of studies that describe the different ways trees communicate and that point out the importance of the communication in the livelihood of a forest. Because corals make up the ‘rainforests of the sea’, this ecosystem is believed to be highly dependent on communication to grow and survive. Many organisms that live in coral reefs, including coral larvae, perceive and are guided by sound when trying to find their way to coral reefs to develop.In light of these preliminary observations, possible genes related to the reception and/or emission of sound were tested to determine its presence in the coral species Cyphastrea. Some of the possible genes are present in organisms very similar to corals while others are seen in plants, bats, and narwhals. The possible genes include WAKL2, Otof, FOLH1, and TRPV. Degenerate primers were developed for these genes which were later amplified via PCR with extracted Cyphastrea coral DNA. Agarose gels were utilized to test for the presence of these genes. Preliminary experiments showed non-specific results during PCR amplification. Data will be presented on the results of whether analogues of these genes from other species are present in Coral.
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