Scientists at the Australian Institute of Marine Science (AIMS) published a study in the journal Science that details how coral embryos from the coral Acropora millepora have the capability to genetically clone themselves before they develop into adult corals.
In their study, Dr. Andrew Heyward and Dr. Andrew Negri subjected coral eggs to water turbulence (pouring the coral embryos floating in seawater over a vertical distance of 30 cm.) in an effort to cause the eggs to break up. The scientists had suspected that the fertilized coral eggs or embryos might break apart because they lacked a protective outer membrane. While the disturbance caused by the turbulence in the waters did indeed fragment a large percentage of the coral embryos (45.1 percent, according to the paper), the now fragmented partial embryos reorganized and continued to cleave. Each individual partial embryo produced from two to eight cell embryos that resulted in smaller but still viable larvae. These larvae then settled and successfully metamorphosed into juvenile corals.
“This effectively mimics the kind of wave height generated by moderate wind speeds where small breaking waves, commonly called whitecaps, occur. That sort of weather is often encountered during a night of coral spawning on the Great Barrier Reef,” Dr. Negri said in a prepared statement released by AIMS. “So it’s highly likely that this fragmentation occurs regularly on nights when corals release their eggs.
In the paper published in science, Heyward and Negri discuss wind speeds near the surface of four Australian reefs on the Great Barrier reef on nights that were predicted to see major coral spawning. Those speeds exceeded 11 knots during 52 percent of the spawning events, which represented winds that were capable of generating whitecaps larger than a meter in size.
Dr. Negri told FishChannel that while Acropora millepora was used in the study, other corals are also very fragile. He notes in their paper to have observed corals from the families Acroporidae, Faviidae, Mussidae, Fungidae, and Occulinidae all to be vulnerable to fragmentation. He also note in the paper Favites chinensis, certain fungid species, Acropora digitifera, and A. tenuis to continue to cleave postfragmentation.