Hydrocoraux

Some Stylasteridae, a family of ornamental corals, are full of secrets...

© IRD/Pierre Laboute

A (delicious) sample forgotten!

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Updated 30.07.2020

When a sample that had been forgotten turned out to be fascinating

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"Sometimes, we have gems right under our noses that we fail to see right away... That’s what happened to a sample of coral from the Stylasteridae family that spent more than a year sitting on my desk turned out to be very interesting from a scientific perspective!

I specialise in micro-organisms that bore into and colonise the limestone substrates of coral reefs. The main micro-organisms I study are cyanobacteria, red and green micro-algae, and fungi, all of which are filamentous. As the micro-organisms chemically penetrate the skeletons of corals, they turn it a specific colour--as long as it does not already have a natural pigmentation.

Several years ago, some of my Italian colleagues asked me to identify the micro-organism responsible for the red-orange colour of the small corals they had just discovered in Indonesia. They were working on Stylasteridae, which are ornamental hydrocorals related to gorgonian corals and reef-building corals. First, they sent me photos, but it was impossible to make an identification from them. I therefore asked them for samples to analyse in due form. Their sample arrived and then just sat there. For a while. I had my own research to conduct and though I could still see the sample sitting there every day, it completely slipped my mind!

Finally, they reached out again and I analysed the sample. What they thought might be a cyanobacteria turned out to be a rarely observed but nevertheless well-known red micro-alga: nori, which is used to make the Japanese dish maki! It undergoes a “hidden” phase of its life cycle during which it colonises limestone substrates like the ones found in corals. Then it leaves the hidden phase behind, forming large, pliable fronds in the reefs where they are subsequently harvested. Up until now, we did not know that it spent time in corals and I was able to write two publications on the subject with my two Italian colleagues.”

by Aline Tribollet, a coral reef biologist & ecologist