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New Order of Marine Creatures Found Masquerading as Sea Anemones

When you see this beautiful creature unfurling its six foot-long tentacles near the seabed like ribbons in the current, you’d be forgiven in thinking that it was an extraordinary sea anemone and moving on. You’d miss an entirely new order of animals.

Reporting in PLOS ONE, an international team of researchers has uncovered a new order of Cnidaria—a group that includes coral, sea anemones, and jellyfish—using DNA analysis. Originally, the researchers set out on a four-year study to classify species of sea anemones according to their evolutionary connections. But when the team looked at 112 species’ DNA, it turned out that one wasn’t a sea anemone at all.

Originally discovered in 2006, the species Boloceroides daphneae (pictured above) was classified as one of the largest anemones known. The new genetic evidence instead shifts the creature outside of Actiniaria (where sea anemones are placed) and into the sub-class Hexacorallia, which includes stony corals. Now named Relicanthus daphneae, the creature is the only species in its own order, separate and no longer able to impersonate anemones. (Here’s a chart to get your phylums, classes, and orders straight.)

tree-of-life-sea-anemone-rodriguez-2014_imagelarge

 The position of Relicanthus daphneae [bolded], previously thought to be a giant sea anemone, was found to be outside of that group, in a new order of animals.

Moving a creature that basically looks and acts like a sea anemone into a new order may seem pointless, but the re-ordering is actually a big deal.

“The discovery of this new order…is the equivalent to finding the first member of a group like primates or rodents,” said Estefania Rodriguez, an assistant curator in the Museum’s Division of Invertebrate Zoology and the lead author of the new publication in a press release.

Putting Relicanthus daphneae in a new order is like putting a chameleon in the same order as crocodiles or finding the first species of primate, only more difficult. If it’s squishy, round, and has stinging tentacles, it’s probably a sea anemone, right?

Not so fast. Because anemones are very simple creatures, they have been grouped by what they lack, instead of what they share. Anemones don’t have skeletons or build colonies, for example (unlike another order such as corals). While sea anemones and Relicanthus daphneae both lack the same characteristics, Relicanthus daphneae never had the characteristics that sea anemones lost in the first place.

“Putting these animals in the same group would be like classifying worms and snakes together because neither have legs,” said Rodríguez.

When animals adapted to life in the deep sea—animals that are often alien and inaccessible to us—aren’t easily classified based on how they look, we need more sensitive methods. New forms of DNA analysis are making this possible, allowing us to see species on a molecular level. Without these methods, we are bound to group organisms together that don’t belong.

Because what creates branches on the tree of life isn’t something you can always see, who knows how many new species are out there, hiding in plain sight.

HT: The American Museum of Natural History
STUDY: Hidden Among Sea Anemones
IMAGES: Top: NERC CHESSO project, Figure created by E. Rodríguez/AMNH; Octocorallia images and sea anemone image courtesy of Bernard Picton/National Museums Northern Ireland

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