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8 September 2003

An obscure 3 cm worm living in mud at the bottom of a Swedish fjord may be one of humankind's closest invertebrate relatives. As part of a larger Wellcome Trust-funded study into the evolutionary relationships of animals, a team led by Dr Max Telford from the University of Cambridge compared three key DNA sequences of the worm, Xenoturbella, with those of other creatures to determine its family relationships.

Previous taxonomic work had placed Xenoturbella with bivalve molluscs (such as mussels and oysters). However, it appears that these conclusions were based on ground-up worms containing molluscs that the worm had eaten. This study reassigns Xenoturbella to the same division as humans.

The animal kingdom is thought to comprise two major divisions: the majority of animal phyla, including the nematodes, insects, molluscs and earthworms, form a group known as the protostomes; the vertebrates, such as fish, amphibians, birds and mammals, as well as our distant relatives the starfish and the little known acorn worms, are in a division known as the deuterostomes. It is this latter division into which Xenoturbella falls.

Further study of this oddity of nature should tell us more about the evolutionary processes that occurred as our ancient ancestors diverged to form the myriad forms of life seen today.

The analysis is published in Nature, 21 August 2003 (Vol. 424: 925-8).

See also

• Enigmatic worm identified as mankind's long lost relative (Press release: 20 August 2003)

External links

• Xenoturbella is a deuterostome that eats molluscs, Nature 424, 925-28 (21 August 2003)
• Dr Max Telford at the University of Cambridge: Research interests