The researchers, led by Tufts professor Michael Levin and undergraduate student Maya Emmons-Bell, cut off the heads of some Girardia dorotocephala -- worms known to regenerate with ease. Then they interrupted the electrical pathways that cells inside the worms use to communicate. By doing so, they were able to mimic make the new heads grow into shapes sported by other, closely related worms.
Brains followed suit, taking on the morphology of related worms instead of that typically seen in Girardia dorotocephala. Examples of these new heads are shown in the bottom row of the image at the top of this post.
It's clear that genes aren't everything. Even in humans, environmental factors can change the way the same genes are expressed. In flatworms, it seems, these non-genomic changes can even be manipulated to change brain and body shape -- at least temporarily. The Girardia dorotocephala worms manipulated in the study reverted to their normal shape a few weeks later.
The researchers hope that studying these non-genomic tweaks can help them learn how to fix birth defects, or even how to make lost body tissues regenerate.