A team of scientists from the University of California, San Diego has successfully identified a pink flatworm-like animal that was previously known as a single species and baffled biologists for almost six decades. Making the discovery in the waters just off of Sweden, the team has used genetic analysis to identify four new species, all in the Xenoturbella genus.
The most unique of these species is the X. churro, a 10-centimeter long purple worm that was named after its resemblance to the popular churro fried-dough pastry that lies at the base of the animal evolutionary tree and was discovered in a cold seep in the Gulf of California approximately 1,700-meters deep. In addition to X. churro, the team discovered three other species, including X. monstrosa, X. hollandorum and X. profunda.
"The findings have implications for how we understand animal evolution," Greg Rouse, lead author of the study, said in a press release. "By placing Xenoturbella properly in the tree of life we can better understand early animal evolution."
The first species to be found in the Xenoturbella genus was X. bocki, which was discovered back in the 1950s off the coast of Sweden. Although it was first classified as a flatworm, followed by a simple mollusk, in the recent years, the Xenoturbella have been classified as close relatives to vertebrates and echinoderms, or even as a distant relative on its own branch.
"When Greg first spotted the worms gliding through a clam field in Monterey Bay, we jokingly called them purple socks," said Robert Vrijenhoek, co-author of the study.
The team has analyzed almost 1,200 of the unique animal's genes to date, which has allowed them to definitively determine that they lie at the base of the evolutionary tree of bilaterally symmetrical animals. With no brain, gills, eyes, kidneys or anus and their only body opening being their mouth, they are classified as evolutionary simple members of the tree.
The findings expand the diversity of the species from one member to five and can help us better understand the evolution of animal organ systems such as brains, guts and kidneys.
The findings were published in the Feb. 3 issue of Nature.
