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7-Foot Mystery Sea Creature Finally Identified After 50 Years

In the 1970s, scientists discovered a brand-new creature living in the deep sea, at the edge of a field of hydrothermal vents (which are essentially superheated underwater geysers). For a long time, no one knew exactly what the creature was. Researchers have shuffled its place on the tree of life several times.

Now, almost 50 years later, scientists have reclassified the beast and placed it in the order of sea anemones, or Actiniaria. The animal’s story is a testament to how much we still have to learn about the deep ocean, which makes up 65% of the Earth’s surface.

A new article about the creature appears in Scientific Reports, co-authored by Professor Mercer R. Brugler of the New York City College of Technology. Brugler also runs a lab at the American Museum of Natural History where high school students and undergraduates assist in research.

The animal, now known as Relicanthus daphneae, is massive for an anemone. It has a column diameter of over 3 feet across, and pale purple or pink tentacles almost 7 feet long, which it can detach at will.

Relicanthus, a new species from a new order of Cnidaria
The animal, now known as Relicanthus daphneae, is massive for an anemone. It has a column diameter of over 3 feet across, and tentacles almost 7 feet long, which it can detach. (Credit: IFREMER/ BIOSPEEDO, courtesy Stephane Hourdez)

In 2006, scientists described the creature for the first time, focusing on its anatomy. Eight years later it was reclassified based on a few pieces of DNA. This time, the researchers have analyzed its complete mitogenome—DNA found in the mitochondria of a cell rather than the nucleus—and re-evaluated some of its body parts (particularly its cnidae, or stinging capsules). Ultimately this new information was used to place it within the Actiniaria. The Relicanthus now also sits in its own suborder, called Helenmonae.

With this new placement, Relicanthus is now “sister” to Actiniaria, meaning they come from a common ancestor and are each other’s closest relatives. The researchers also sequenced the mitochondrial genomes of 14 other sea anemones, more than doubling available sea anemone mitogenomes.

“We liken it to as if we had seen a whale for the first time 50 years ago and still did not know if it was a fish or a marine mammal,” Brugler said. “This study highlights how little we know about our own planet, the deep sea, and marine invertebrates in particular.”

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Mercer Brugler (Associate Professor, Biological Sciences) | Profile 1 | Profile 2