In fact, the Planarians regeneration is so rapid that studies conducted in 1898 showed that even dissected to a tiny one 276th of its original size, the planarians could regenerate itself.
However, what makes these invertebrates even more spectacular was a recent study performed by Michael Levin, a Tufts University professor.
Published in the latest edition of the Journal of Experimental Biology, Levin conducted a study on Planarians cognitive functions and regenerative functions simultaneously.
Like many flatworms, or worms in general, planarians strongly dislike bright lights. They would much rather be in a warm, moist environment than a dry, hot one. Using this information, Levin vigorously trained his planarians to eat food in a very bright light.
Utilizing two different groups of planarians, Levin placed group 1 on a rigorous surface, while another on a flat surface. Each group had part of their environment illuminated by a light, where a piece of liver was placed.
Using a recording device, tracking analysis technology and measuring technology, Levin filmed the planarians over a ten-day period to see how easily each group would be to train. Those with a more rigid surface were more susceptible to the bright light and were less hesitant to eat in the bright light than those on a flat surface.
As a hypothesis, Levin suspected that if planarians were able to retain their memory after complete head severance, those on the rigid surface would be more susceptible to light exposure than those on the flat surface.
Analyzing this information, Levin severed all the heads on the worms and gave them a 14-day rest period to regrow their heads and brains.
Both group of worms were placed in a Petri dish and studied for their aversion to light. As suspected, both group of planarians were hesitant to go toward the light at first, however those who were on the rough terrain adapted much quicker.
Furthering his point, Levin then placed the planarians on a four-day break and placed them all back onto a Petri dish with light. Those on a rough terrain were much more susceptible to light exposure and moved around much more freely than those who were in the Petri dish.
This experiment provided Levin with the conclusion that the worms were able to retain their cognitive memory even after their heads were severed. At a minimum, planarians can retain memory for 14-days, enough to regrow their brains and restore the information.
How Their Memory is Stored
There is no definite answer as to how or where these planarians place their memories. It could be through their nervous system or through an unknown cellular memory function.
However, it is definite that planarians are able to store memories and regenerate all parts of their cellular body even when severed to a single miniscule portion.