Traditionally, we had attributed the ability to store and retrieve information to organisms with a nervous system, a function that gives living beings a clear advantage to search for food more efficiently or even avoid environments that are harmful or dangerous for their survival. But now, a new study published in the journal PNAS challenges this theory head-on. A team of researchers from the Max-Planck Institute for Dynamics and Self-Organization (MPI-DS) and the Technical University of Munich (TUM) has identified that an organism, specifically the slime mold Physarum polycephalum , stores memories, despite having no system highly strung.
The strangest way of life in the world
This unicellular organism that we can find in many humid and dark environments (litter or among the rotten debris of forests) does just that: it is capable of storing and retrieving information about its environment; an impressive feat considering they lack any form of central nervous system.
Despite their name, slime molds are neither molds nor fungi, but eukaryotes, that is, they belong to the same domain as humans and other animals. However, they are not your average single-celled organism, they consist of a collection of individual cells that have come together in a rather particular unified way, complete with multiple nuclei enclosed in a single giant cell.
These curious organisms, whose single amoeba-like cell can stretch several centimeters or even meters, can be cut into pieces, but at some point they will fuse again. It is also possible to see how several of these organisms join together to form an even larger organism.
A form of ‘intelligence’
According to the researchers, slime mold, which has neither brain nor neural structure, “weaves memories of encounters with food” into its body and uses those memories to make future decisions. “Given the simplicity of this living network, Physarum’s ability to form memories is intriguing,” clarifies Karen Alim, professor of biological physics at Munch Technical University, and co-author of the work. “It is remarkable that the body relies on such a simple mechanism and yet controls it in such a fine way.” And you don’t need a brain for it.
Where do they store that information then?
Since it seems that this type of navigation necessary to avoid dangers and search for food should require a brain to store data on where the organism has been, and since we have already commented that it does not have this attribute, how do you remember? Turns out, the mold reads the slime trail it leaves behind. That trail has different chemical qualities depending on whether the mold had detected food when it was on the trail. By reading these chemical qualities upon bumping into a trail it has previously left, the slime mold knows whether or not it is on the right track, effectively turning its own trail into a memento of where it has been.
Thus, the researchers discovered that the body weaves the memories of encounters with food directly into the architecture of the body in the form of a network and uses the stored information to make future decisions. “It is very exciting when a project develops from a simple experimental observation,” Alim continues.
“The thick tubes of the network act as highways in traffic networks, allowing rapid transport of information throughout the body,” adds Mirna Kramar, co-author of the study. “Previous encounters imprinted on the architecture of the network influence the decision on the future direction of migration.”
Referencia: Encoding memory in tube diameter hierarchy of living flow network. Mirna Kramar and Karen Alim. PNAS (2021).DOI:https://dx.doi.org/10.1073/pnas.2007815118
