Biologists at Tufts University in Medford, Massachusetts, have successfully swapped the head of one species of flatworm and replaced it with the head and brain of another species. Published online in the International Journal of Molecular Sciences on Nov 24, the findings reveal that evolution is controlled by more than genetics alone.

The researchers did not meddle with the flatworm’s DNA, instead they manipulated the electrical synapses in the worm's body. This could bring a better understanding of how physiological functions impact the body shape, which will hopefully help doctors treat birth defects and regenerate body parts.

The team used Girardia dorotocephala, a small freshwater flatworm that has a remarkable regenerative capacity. They induced it to grow the head and brain shapes of other flatworm species by interrupting the gap junctions. These are protein channels where cells send electrical impulses to relay information with each other. They did not only alter the overall shape of the head, they also changed shape of the brain and the distribution of the worm’s stem cells as well, TuftsNow reports.

After the experiment, some grew rounded heads like S. Mediterranea, triangular heads like D. Japonica, heads with thick necks and pointy ears like P. felina, while others maintained their normal pointy heads with two earlike projections. The results depended on how closely related these worms were on the evolutionary family tree.

However, the change was only temporary. Within 30 days, the G. dorotocephala returned back to their original head structure. The researchers are not yet sure why this happened. Hence, they intend to conduct more research to solve this question.

“We've demonstrated that the electrical connections between cells provide important information for species-specific patterning of the head during regeneration in planarian flatworms,” said Maya Emmons-Bell, an undergraduate student of Tufts who co-authored the report. “This kind of information will be crucial for advances in regenerative medicine, as well as a better understanding of evolutionary biology."

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