Researchers: Xyloplax are Actually Starfish
Posted on May 2, 2011
Researchers have discovered that Xyloplax, small disk-shaped animals, are actually starfish that have lost the large star-shaped, adult body from their life cycle. A team of scientists combined embryological observations, genetic sequencing, and supercomputing to determine that the animals - once thought to represent a new class of animals - are actually starfish.
Daniel Janies, Ph.D., a computational biologist in the department of Biomedical Informatics at The Ohio State University (OSU), and his colleagues theorize that Xyloplax differs from other starfish species because it is progenetic - that is, it has a rare, truncated life cycle that leaves the mature organism with features retained from its juvenile stages. For example, the arms of a starfish typically grow axially, like spokes of a wheel, as they develop from juveniles to adults, whereas Xyloplax grows along its circumference, like the wheel itself, and never develops arms.
Janies says, "Irrespective of method or data sampling scheme, our results show that Xyloplax evolved from within starfish. Xyloplax is just a little starfish that has a strange body plan and habitat, so strange that many could not recognize it as a starfish until we unlocked its genome and development."
You can read a press release about the research here. The full paper was published in the journal Systematic Biology.