You can chop a flatworm into pieces, and the new ones will still "remember" which genes were turned off in the original.
bioRxiv · March 13, 2026 · 10.64898/2026.03.11.711021
Why it matters
While most animals reset their genetic markers during development or reproduction, planarians can pass down a specific molecular 'silencing' memory to new cells during total body regeneration. Remarkably, they do this without the specific enzymes previously thought to be the only way for life to maintain this kind of long-term epigenetic memory.
From the abstract
How cells and organisms preserve molecular memory is a central question in biology. Chromatin states can maintain cellular memory in animals, yet DNA and histone modifications are typically reset in the germ line and early embryo. In Caenorhabditis elegans, RNA-dependent RNA polymerases (RdRPs) amplify small RNAs and enable transgenerational gene regulation. However, many organisms, including mammals, lack canonical RdRPs. Here we find that planarians, highly regenerative flatworms that lack can