Creature clones itself to avoid becoming fish food

  • 18:00 13 March 2008
  • news service
  • Catherine Brahic
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Bottom-dwelling sand dollars are related to sea urchins and sea stars (Image: GNU licence)

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Cloned larvae (right) are smaller than non-cloned larvae (scale bar: 0.2 mm) (Image: Dawn Vaughn)

It's a novel escape route that makes a mockery of the status of the individual: if you run the risk of being eaten, just clone yourself. That is the approach taken by the larvae of sand dollars – marine animals related to sea urchins.
Fish are voracious predators of sand dollar larvae. Dawn Vaughn and Richard Strathmann of the University of Washington, Seattle, found that when they put four-day-old sand dollar larvae in a tank with fish mucus, the larvae cloned themselves.
They did this by either splitting in two or by producing a small bud which detached itself and developed into a new larva. Either way, the clones were smaller than the original larvae. Sand dollars did not clone themselves if there was no fish mucus in the water.
Vaughn and Strathmann believe the larvae sense the mucus, interpret it as a sign that fish are nearby, and respond by producing clones.
Better odds

There is no parental care in this species. "[The mother] is on the seafloor," says Vaughn. "She has no idea what types of risk her offspring are going to meet, so the larvae respond to cues from predators."
Cloning gives the larvae's genes a greater chance of survival in two ways. With two copies around one is statistically more likely to escape predation. Also, the smaller clones are less likely to be detected by