21
August 2003
Xenoturbella: Diet of worms
Xenoturbella is a small and simple marine worm, first described in 1949, that has proved troublesome to taxonomists, what they call "enigmatic". First described as a platyhelminthes flatworm, it has since been claimed as a relative of the hemichordates and echinoderms, among other things. In 1997 it was reported that Xenoturbella produced mollusc-like eggs and contained mollusc-like DNA. Despite looking nothing like one, Xenoturbella, it seemed, was a mollusc with an adult form that had become degenerate. But now it emerges that this brief sojourn with the Mollusca was the result of DNA contamination from mollusc embryos that had been eaten by the worm. New evidence shows that Xenoturbella is a primitive deuterostome, related to acorn worms and echinoderms. As such it is probably the most primitive extant creature in the group of organisms that includes the chordates, and therefore humans.
Xenoturbella is a deuterostome that eats
molluscs
SARAH J. BOURLAT, CLAUS NIELSEN, ANNE E. LOCKYER,
D. TIMOTHY J. LITTLEWOOD & MAXIMILIAN J. TELFORD
Nature 424, 925–928 (2003); doi:10.1038/nature01851
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Zoology: You aren't what you eat
HENRY GEE
An obscure marine worm does not belong among the molluscs, as had been
thought. Rather, it has a claim to being the most primitive extant member
of the group of animals that includes vertebrates.
Nature 424, 885–886 (2003); doi:10.1038/424885a
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