‘Sea anemone’ not a sea anemone, new research says


This video is called Wonderful World – Sea anemones.

From Wildlife Extra:

Study of sea anemones leads to new branch on the tree of life

A deep-sea animal with tentacles more than six and a half feet long was once thought to be one of the world’s largest sea anemones, but has now been reclassified as belonging to a new order of animals and is not a sea anemone at all.

This animal, previously called Boloceroides daphneae, was discovered in 2006 in the deep east Pacific Ocean and labelled as one of the largest sea anemones in existence. But a new DNA-based study led by the American Museum of Natural History shifts it outside of the tree of life for anemones. Instead, researchers have placed it in a newly created order—a classification equal to carnivoria in mammals or crocodilia in reptiles—under the sub-class Hexacorallia, which includes stony corals, anemones, and black corals. The new name of the animal, which lives next to hydrothermal vents, is Relicanthus daphneae.

Relicanthus daphneae is a classic example of convergent evolution, the independent evolution of similar features in species of different lineages.

“Even though this animal looks very much like a sea anemone, it is not one,” said Estefanía Rodríguez, lead author of the report published in the journal PLOS ONE, and an assistant curator in the Museum’s Division of Invertebrate Zoology. “Both groups of animals lack the same characters, but our research shows that while the anemones lost those characters over millions of years of evolution, R. daphneae never had them. Putting these animals in the same group would be like classifying worms and snakes together just because neither have legs.

“The discovery of this new order of Cnidaria—a phylum that includes jellyfish, corals, sea anemones, and their relatives—is the equivalent to finding the first member of a group like primates or rodents. The difference is that most people are far more familiar with animals like chimpanzees and rats than they are with life on the ocean floor. But this amazing finding tells us that we have so much more to learn and discover in the ocean.”

Rodríguez, along with an international team of researchers, conducted a four-year study to organise sea anemones in a “natural,” or phylogenetic way, based on their evolutionary relationships. Sea anemones are stinging polyps that spend most of their time attached to rocks on the sea floor or on coral reefs. Although they vary greatly in size and colour, anemones have very few defining structures. As a result, classifying these animals based on morphology alone can be difficult.

“Anemones are very simple animals,” Rodríguez said. “Because of this, they are grouped together by their lack of characters—for example, the absence of a skeleton or the lack of colony-building, like you see in corals. So it wasn’t a huge surprise when we began to look at their molecular data and found that the traditional classifications of anemones were wrong.”

The researchers compared particular sections of DNA of more than 112 species of anemones collected from oceans around the world. Based on genetic data and the organisation of their internal structures, the scientists reduced the sub-orders of anemones from four to two.

For now, Relicanthus daphneae is the only species in the new order, but researchers hope to change that. “Although we’ve long known about the existence of this giant animal, it’s only in recent years that we’re really starting to understand where it fits into the tree of life,” Rodríguez said. “So imagine what else is still out there to discover.”

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