Plasmodial slime mold

Nature never ceases to amaze us and this organism is proof of this. Slime mold or plasmodial slime mold are names given to a group of eukaryotic organisms that look like a gelatinous substance and move through their habitat absorbing fungi, decaying organic matter and even other slime molds.

They can be of different colors, depending on the species; most are transparent, yellow or white, but they can also be found reddish, green and blue. They can also reach up to one meter in diameter.

Fungus, bacteria, animal?

For a long time it was believed that they were a species of fungi, this was mainly due to the fact that their life cycle is very similar and similarities were also found with some bacteria, but that does not imply that they are related. They were also classified as animals because they have a cell membrane like animal cells. They are currently considered protist amoebae.

Amphibian amoebas

Plasmodial slime molds start life as haploid spores (which have a single set of chromosomes) that are easily spread by wind, rain, and animals. When conditions are favorable, the outer shell of the spore breaks and an amoeboid cell emerges. If the cell is in water, it can develop flagella that it uses to swim, and if the environment dries up, it loses them and crawls to get around. If conditions are unfavorable, the amoeba can coat itself in a protective coating and hibernate until conditions are favorable again.

If two amoebas come together and are compatible they can fuse to form a diploid amoeba (which has two sets of chromosomes). Compatible haploid amoeba pairs can come from spores of the same or different ancestors. As it feeds and grows, its nuclei continue to divide and therefore it is called plasmodial.

Slime mold can travel over surfaces at approximately 1 cm per hour. To do this, it forms a network of vessels in which the cytoplasm and nutrients are transported from one side to the other. They feed by crawling on their food, suffocating and absorbing it. This type of feeding is called phagocytosis. A slime mold's diet is primarily made up of bacteria, fungi, and decaying organic matter, and they find their food by smell.

If you cut a plasmodial slime mold into pieces, each fragment will continue its life as an individual, and if it comes across a piece that shares genetic material, they fuse together again. However, if two different slime molds meet, the larger one will devour the smaller one.

A fluffy death

If certain conditions are met, the slime mold can be primed to sporulate. These conditions are that it runs out of food and that there is light. To do this, the plasmodium looks for a suitable place that is elevated to facilitate the dispersal of the spores. When it finds it, it begins to lose its network of veins and develops stems on which sporangia grow, which contain the spores. The spores are produced through meiosis so they are haploid. At this stage, it has a foam or sponge-like texture and can even be mistaken for synthetic foam.

Brainless but smart

Slime molds lack any structure that could resemble a brain: they are one huge cell with no neurons or nervous system. However, various studies have shown that these organisms are capable of remembering and apparently learning, and they have also managed to solve problems and adapt to environmental stimuli.

There are certain substances that slime molds avoid, such as caffeine and quinine (harmless to them, but bitter) or salt, and there have been experiments that show how they can adapt and ignore the presence of these substances, in a similar way to how humans can ignore certain repetitive sensations such as a continuous sound or the sensation of clothing on the skin. In addition, they can pass on what they learn to other fragments: when a habituated fragment and a non-habituated one were fused, after about three hours, the time it takes for veins of cytoplasm to form between the pieces, the non-habituated fragment had acquired the habituation, and it kept it even when the pieces were separated again.

A study in Japan showed how slime molds build very efficient networks of vessels to transport nutrients when they feed. In this experiment, oat flakes were placed in positions representing the main cities of the Greater Tokyo Area; when the slime mold began to form its vessels, the resulting network closely resembled the real Tokyo rail network, with comparable cost, efficiency, and fault tolerance.

Slime mold

Tokyo rail network