Butterfly wings, beetle horns reveal how bodies develop

Caterpillars treated to stunt the growth of their future hind wings developed into butterflies with abnormally large front wings. At least that's what two Duke University (Durham, NC) biologists have discovered. And they also found that dung beetles treated to stunt the growth of their horns sprouted larger eyes. The discoveries represent more than biological curiosities, Professor of Zoology Fred Nijhoust and postdoctoral fellow Douglas Emlen report. It constitutes, they say, the first clear demonstration that living organisms arise not only through the direct read-out of some genetic recipe, but also through more subtle and mysterious processes of competition between growing body parts for resources. Such tradeoffs, the researchers feel, may make inherited changes in some traits or structures appear genetic, when they are not. In their experiments, the scientists performed tiny incisions in caterpillars to remove one or both of the small, fleshy discs that would develop into the hind wings once the caterpillars underwent metamorphosis. Instead, the emerging butterflies had abnormally enlarged front wings. In the case of the beetles, the adult males with reduced horn size had correspondingly enlarged compound eyes. "These experiments demonstrate that the control of how big an organ or tissue grows doesn't lie entirely within that organ or tissue," Nijhout explains. The scientists plan further experiments with the hope of discovering that insects will provide lessons about development in higher animals. E-mail [email protected].