An international team of scientists from Australia and the United States may have finally determined the identity of a worm-like animal that had baffled Swedish biologists for close to six decades.
Since the discovery of the deep-sea creature known as Xenoturbella back in 1950, researchers have long sought to identify which part of the animal family tree it belonged to.
This changed when scientists from the Western Australia Museum, the Monterey Bay Aquarium Research Institute (MBARI) and the University of California, San Diego found four new species of the same kind of animal.
Lead investigator Greg Rouse from UC San Diego's Scripps Institution of Oceanography described the creatures as seemingly deflated balloons or purple socks that were left on the floor.
The animals have no brains, guts or even eyes. They only have gaping mouths that allow them to take in food and release waste.
Earlier scientists had difficulties in studying the creatures because only one species was identified.
Rouse explained that the Xenoturbella were mistakenly tagged as mollusks because researchers had sequenced the DNA of what the creatures eat instead of their own.
It had also been thought that the sock-like species used to be highly sophisticated animals that discarded all of their complex features as they continued to evolve.
The finding of the four new Xenoturbella species, however, gave Rouse and his colleagues an opportunity to examine the animals in detail.
They made use of remotely operated vehicles (ROVs) to capture the deep-sea creatures on tape for the first time.
Two of the specimens Rouse and his team found were a 20-centimeter-long (7.9-inch) species named Xenoturbella monstrosa and a 10-centimeter (4-inch) species named Xenoturbella churro.
The Xenoturbella churro received its name because its body resembled the deep-fried pastry that is popular in several Latin American countries.
The researchers were able to conduct extensive genetic analyses on the four new species. This allowed them to corroborate that the creatures belong to a single primitive group located at the bottom of the animal tree of life.
Rouse and his team are now planning to carry out follow-up observations of Xenoturbella to find out how these animals are able to consume mollusks despite not having guts.
The findings of the international study are featured in the journal Nature.
