Here is a picture of a local example of the slime mold Fuligo septica, also commonly known as dog vomit fungus, although it is no longer classified as a fungus. This is a somewhat desiccated specimen, but on YouTube you can see them viscous and throbbing. And hunting. For they are mobile, and they hunt for the bacteria and spores that feed them. In his latest book, Life’s Edge, Carl Zimmer writes that this single-celled organism “can get as big as a throw rug”. Picture a viscous throw rug creeping along at around a centimeter per hour. Now realize that this is a single huge cell, with thousands of nuclei.
Slime molds were long understudied, “because of their unprepossessing nature,” Wikipedia tells us about the Myxogastriae, the class of slime molds that includes Fuligo septica. The lab in Zimmer’s story grows Physarum polycephalum, which, like the above, can dry up into a “sclerotium”. Months later the sclerotium can be revived by water and food. This is known as cryptobiosis.
“Cryptobiosis or anabiosis is a metabolic state of life entered by an organism in response to adverse environmental conditions such as desiccation, freezing, and oxygen deficiency. In the cryptobiotic state, all measurable metabolic processes stop, preventing reproduction, development, and repair. When environmental conditions return to being hospitable, the organism will return to its metabolic state of life as it was prior to the cryptobiosis.” (Wikipedia)
The undisputed star of cryptobiosis is the tardigrade, which demonstrated that you don’t need to be macroscopic to have charisma. About .02 inches fully grown, members of the phylum Tardigrada have been dubbed “water bears” and “moss piglets”. They really burst on the scene with their trip to outer space in 2007. Slime molds and tardigrades have both been found in earthly environments including deserts, forests, water, and snow.
But slime molds are, naturally, slimy, at least in their most visible form. Nothing like slime to kill charisma. However, their brainless intelligence has been causing a stir. Brainless intelligence.
“Information processing is an interesting component of biological systems. Although the brain has evolved to perform this specific function, information processing is possible without a brain, and organisms as simple as amoebae are much more intelligent than generally thought. For example, the true slime mold Physarum polycephalum can solve a maze and certain geometrical puzzles, in order to satisfy its needs for efficient absorption of nutrients and intracellular communication .”
https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/33004/1/PhysRevLett_100_018101.pdf
They not only can solve mazes, but they find the shortest path through them. They can create their optimal mix of protein and carbohydrates while connected to multiple sources of food none of which have the desired ratio. They don’t simply mix the sources, but they draw the correct amount from each, solving a version of a tricky resource allocation problem that mathematicians call the Knapsack Problem. If you make a map of cities using wet oat flakes for the cities and you add a starter mass of slime mold then in a few days you will have a network that resembles an efficient public transportation network.
“Transport networks are ubiquitous in both social and biological systems. Robust network performance involves a complex trade-off involving cost, transport efficiency, and fault tolerance. Biological networks … are likely to yield reasonable solutions to such combinatorial optimization problems. Furthermore, they develop without centralized control and may represent a readily scalable solution for growing networks in general. We show that the slime mold Physarum polycephalum forms networks with comparable efficiency, fault tolerance, and cost to those of real-world infrastructure networks–in this case, the Tokyo rail system.”
https://pubmed.ncbi.nlm.nih.gov/20093467/
These slimy bags of protoplasm seem to have a bright future ahead. Wait, wrong metaphor. They move towards the shade, as in this experiment in which Physarum polycephalum guides a six-legged robot away from the light.
https://www.newscientist.com/article/dn8718-robot-moved-by-a-slime-moulds-fears/