Yet scientists studying worms, primarily those called Caenorhabditis elegans, have increasingly found that genes from these simple animals resemble genes in more complex creatures. In addition, the related genes are frequently used in a similar manner. As a result, S nchez is operating on the assumption that the regeneration strategy used by planaria resembles the one employed by urodeles and may provide insight into the human failure to regenerate. There's some evidence supporting this contention. When cut in half, the worms form blastemas similar in architecture to those seen when researchers amputate the limbs of a urodele.
Planarian regeneration does have clear differences, however.
The most significant seems to be that the worms do not dedifferentiate cells to create the blastema. Instead, planaria turn to cells called neoblasts. Scattered within the planarian body, neoblasts apparently remain in an unspecialized, stem cell state, which enables them to differentiate into any cell type. Wherever planaria are cut, the neoblasts migrate to the site and form a blastema by themselves. S nchez' colleague Phillip Newmark has kept planarian neoblasts alive in petri dishes for several weeks, an advance the researchers hope will allow them to genetically alter the animals.