Elkhorn Corals May Be the Longest-Lived Animals in the World

Researchers from Pennsylvania State University have made a surprising discovery: elkhorn corals may have been on earth for over 5,000 years. Along with experts from the National Marine Fisheries Service and Dial Cordy & Associates, it was determined that the Acropora palmate in the Caribbean and Florida has an extraordinary level of resiliency.

"Our study shows, on the one hand, that some Acropora palmata genotypes have been around for a long time and have survived many environmental changes, including sea-level changes, storms, sedimentation events and so on," said Iliana Baums, an associate professor of biology from Penn State and a co-author of the research published in Molecular Ecology. "This is good news because it indicates that they can be very resilient. On the other hand, the species we studied is now listed as threatened under the U.S. Endangered Species Act because it has suffered such sharp population declines, indicating that there are limits to how much change even these very resilient corals can handle."

Baums believes that the results are vital for scientists to determine how corals respond to past, present, and future environmental change. "Previously, corals have been aged by investigating the skeletons of the colonies or the sizes of the colonies," Baums explained. "For example, bigger colonies were thought to be older. However many coral species reproduce via fragmentation, in which small pieces break off from large colonies. These pieces look like young corals because they are small, but their genomes are just as old as the big colony from which they broke. Similarly, the big colonies appear younger than their true age because they became smaller during the process of fragmentation."

Baums and her fellow researchers used genetics to determine the age of the Acropora palmate by pinpointing when the egg and the sperm originally met to form the genome of the coral colonies, then tracking the number of mutations that accumulated in the genome from that point in time.

"This was surprising, as previously, only cold-water corals were found to be older than 1,000 years," shared Baums. "Knowing the age of individuals in a population is important for understanding their population history and whether the population is increasing or decreasing. It is especially important when the population under study is threatened."

Despite their longevity, Baums believes the Acropora palmate may not be immune to the effects of climate change especially since it's on the IUCN Red List. "If Acropora palmata genomes have persisted over hundreds to thousands of years, it implies persistence through substantial environmental changes, and possibly gives hope that they can survive additional anticipated climate change. What is different now is that human-induced climate change is happening at a rate that far exceeds past environmental changes. Therefore, the coral's past ability to survive environmental change does not necessarily predict their future success."