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A mystery is solved

Two views of the newly discovered Enteropneusta. Photo: MAR-ECO 
The remarkable red worm discovered by MAR-ECO scientists turns out to belong to a completely new family. In fact it is not a worm, as they initially thought, but an “enteropneust” that has more in common with vertebrate. An article in a recent issue of “Nature” solves the mystery.

During dives to 2,300 - 2,400 m on the Mid-Atlantic Ridge, using remotely operated vehicles (ROVs), the MAR-ECO project, under its Norwegian leadership, observed some remarkable red worm-like creatures which lay rather passively on the sea-bed and left spiral mud-casts behind them. These animals were seen for the first time during dives made by the Russian “MIR” submersibles in the Charlie-Gibbs Fracture Zone in June 2003. The following summer, during the two-month-long MAR-ECO expedition, the animals were filmed again, but not captured. For the MAR-ECO scientists they remained a mystery - until now, that is.

Working together with an American group who have found similar animals in the Pacific Ocean, project scientists (Mike Vecchione of the Museum of Natural History in the USA and Andrey Gebruk of the P.P. Shirsov Institute of Oceanography in Russia) have since been able to confirm that the red creatures should be placed in a new family in the Class Enteropneusta or acorn worms.

Mike Vecchione
This has been reported in the 17th March issue of “Nature”, thus solving a mystery that triggered an international race to find out what these animals really were. A single individual from the Pacific was sufficient to confirm the identification.

Acorn worms are actually not worms at all. In anatomical terms, they have more in common with vertebrates such as fish, amphibians, reptiles, birds and mammals. They belong to a small phylum called the Hemichordata, which are animals with a primitive “notochord”, an anatomical feature that they share with the “true” vertebrates (Phylum Chordata) which also include ourselves.

“It is a rare and pretty sensational event when a new family is discovered, and exciting that some of the best video recordings were made from the Norwegian research vessel “G. O. Sars” with the aid of the ROV “Bathysaurus”, says Odd Aksel Bergstad, a research scientist at the Institute of Marine Research and MAR-ECO project manager.

Andrey Gebruk
Andrey Gebruk, one of the authors of the “Nature” article, was recently in Bergen, where he worked on the recordings from the Aglantha and Bathysaurus ROVs.  Gebruk is a member of the MAR-ECO steering group and leads the project’s studies of benthic (bottom-living) fauna. He took part on the “G. O. Sars” cruise in 2004 as well as the Russian-American MAR-ECO cruise with RV “M. Keldysh” in June 2003, when the manned submersibles “MIR-1” and “MIR-2” made dives to 4,200 m. Gebruk leads the benthos group at the P.P. Shirsov Institute of Oceanography in Moscow (a major institute belonging to the Russian Academy of Sciences). He was accompanied in Bergen by Elena Krylova of the same institute, who also has wide experience of deep-sea diving in manned underwater vehicles.


~ Watch a video of the new Enteropneusta species
~ Read more about Hemichordata and Enteropneusta
~ Contact persons: Odd Aksel Bergstad, Michael Vecchione and Andrey Gebruk

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