Discovery of the World’s Oldest Living Organism

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Living to a ripe old age may be a dream to most humans and a possibility for only a few animals and plants. Not so for seagrasses in the Mediterranean!

An international team of scientists and researchers from various organizations including the University of Algarve in Portugal have announced their find of the world’s oldest known living organism. Said study was carried out between 2005 and 2008 for the field work aspect while the laboratory investigation was carried out at the Sea Sciences Center of the University of Algarve in 2009. The results were published in the Public Library of Science One journal.

The researchers believe that the meadow of seagrass known as Posidonia Oceanica located along a 9-mile wide stretch off the Spanish island of Formentera is 100,000 years old at least with the possibility of it being 200,000 years old by some estimates. This means that said patch of seagrass began growing in the late Pleistocene era when humans first emerged on Earth.

According to Ester Serrão from the Sea Sciences Centre of the University of the Algarve, leaders of the Portuguese team, “We discovered specimens of Posidónica oceânica that could be between 10,000 and 100,000 years old and possibly more. Never before has such a living organism of this age been found on earth.”

Still according to Ester Serrão, “The species has been known for a long time, but what we have now discovered is where one individual starts and ends.” She added that, “when we see a marine prairie, we don’t know straight away if it came from one seed or several.”

The study then aimed to measure the area covered by a single seagrass, calculate its age and study its genetic characteristics. These were made possible through existing knowledge of seagrasses growing by 4 centimeters every year and through modern techniques in DNA testing.

Based on these methods, the team discovered that a single individual can occupy a space anywhere from 4 to 15 kilometers in length. It must be noted that seagrasses fan out over the area by producing genetically identical clones of themselves ad infinitum. This means that the seagrasses in a particular meadow came from the same single seed from hundreds of thousands of years ago.

According to Sophie Arnaud-Haond, co-author of the study and hailing from the French Research Institute for the Exploration of the Sea, “They can reproduce sexually through flowering and recombination of male and female genomes, or clonally through the exact replication of the genome of an individual forming a new plant module through clonal growth.”

However, a few of the meadows of seagrasses may not be borne of cloning but of other means of transporting the seeds and plants to other locations. The seagrasses – or at least, pieces of it - may have detached from the main growth, transported by the ocean currents, and grew on the sediment deposits. This would mean that the 15-kilometer stretch of seagrass is 100,000 years old.

Other individuals of the Posidonia Oceanica species have been determined to be at least 10,000 years of age. These seagrasses came from the 1,544 samples gathered from 40 marine prairies of the Mediterranean Sea over an area 3,500 kilometers long.

How did the Posidonia Oceanica species survive for so long? There are two viable explanations.

First, the seagrass has an exceptional ability to adapt to changes in its environment even the drastic ones. When the seagrass began its life in the sea, the ocean temperatures were lower by 10°C to 15°C than it is at present.

Second, the seagrass lacked native competitors and predators. Although green turtles and other animals feed on the seagrass, its rate of growth more than matched the consumption. As a result, the Posidonia Oceanica grew so vast and so old.

However, the researchers warn that the world’s oldest living organism is in danger. Despite its resistance to environmental changes, longevity and cloning ability, it is estimated that seagrass meadows have declined by 10% over the last century. The possible culprit is maritime pollution, which makes it harder for the seagrasses to undergo photosynthesis.

Unfortunately, this is bad news for the marine animals like the green turtle that depend on seagrasses for their food. Future generations may not enjoy this link to an ancient Earth.


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Published in: Portuguese Life