In order to protect themselves against threats such as ocean acidification, algal takeover and increases in the population of harmful microbes, coral reefs have their own type of immune system, much like humans. A new study has revealed a particular molecule in these reef ecosystems that mirrors its role in humans, suggesting that the immune function of the molecule stems back at least 550 million years.
The team of researchers behind the study set out to reveal the dynamics of healthy ocean ecosystems and sought to do so by examining the molecular makeup of coral reef ecosystems. The research was a part of the National Geographic Society's Pristine Seas project.
"Our oceans are rapidly declining and we need to understand what's normal before there's no 'normal' left," said Rob Quinn, scientist from the University of California, San Diego and lead author of the study. "We need to find out what healthy reefs look like so we can identify those transitioning to unhealthy."
Quinn and his team analyzed coral tissue samples that were gathered from reefs off the Southern Line Islands in the central Pacific Ocean, which are considered to be the cleanest and most remote reef systems in the world.
After analyzing the molecular composition of the tissue samples using mass spectrometry, the team noticed that the platelet activating factor (PAF) - an important molecule in humans and other species due to its role in the immune system - stood out.
"It was basically the most abundant molecule we detected in coral," Quinn said.
The team then used genetic sequencing to compare the molecular and genomic makeup of tissue from corals that compete with algae in the Southern Line Islands, revealing that PAF and related genes were most present in coral that was damaged by algae, suggesting that its production is a response to stress much in the same way that it responds to infection in the human body.
Corals and humans likely split off from each other on the evolutionary tree around 550 million years ago, making it likely that PAF came into play around that time and has played a role in the immune systems of numerous species since.
"Despite the complexity of our immune system, a lot of the same things have been going on for 550 million years," Quinn said.
The findings were published in the April 26 issue of the Proceedings of the Royal Society B.