"We didn't know how they would respond, or even whether they would respond," she said.
Within 24 hours, the larvae developed clone buds that ultimately detached and formed new larvae that were much smaller than the original organism. The original larvae also were substantially reduced, to about half their original size.
Larvae that were not exposed to fish mucous did not clone themselves.
Vaughn suggests that cloning might be an adaptive response for the organism to try to ensure its survival in some form if a predator strikes. That is accomplished if only one of the two larvae that result from cloning survives.
"From their perspective, if both the original larva and the clone survive that's great then there are two of you," she said.
Vaughn noted that reduced size because of cloning could affect survival later in the sand dollar's life. In many species, greater size reduces the chances of predation, and sand dollars that have gone through the larval cloning process turn out to be smaller than non-clones when they settle to the sea floor. It is not yet clear whether that makes them more vulnerable to predators at that point, though she plans to examine that in the next stage of her research.
"At this point we would suggest that might be the trade off. But if they don't avoid predation in the first place they would never get to the sea floor," she said.
Richard Strathmann, a UW biology professor and Vaughn's doctoral adviser, is co-author of the paper. The work was funded by the National Science Foundation and Friday Harbor Laboratories.
Vaughn noted that the larval sand dollars' response did not appear to depend on the species of fish that generated the mucous. Instead, it appears the larvae reacted to the bacterial breakdown of the mucous, and interpreted that as the presence of a potential predator.
"They might respond to
|Contact: Vince Stricherz|
University of Washington