Ever since scientists first tried to classify slime molds, they have been erroneously classified as plants, animals, and, in particular, fungi. This is because they are commonly found in the same ecosystems as fungi and because they create structures to help spread their spores like their fungi counterparts do.
Photos from open sources
Molecular methods of grouping life forms by comparing their DNA have helped to better understand the slime molds’ unique heritage. However, their exact place on the tree of life is still unclear.
Despite their superficial resemblance to fungi, many aspects of the biology of slime molds are strikingly unique. This yellow slime blob may not look like much, but it’s actually a vicious predator of bacteria, yeast, and other micro-organisms, including fungi.
Although they can get quite large – up to several square meters in diameter – each slime mold is a single cell containing millions of nuclei and all the other complex machinery that resides inside cells like ours.
The “body” of a slime mold is a network of veins and tubes that can move at speeds of up to five centimeters per hour to find and capture their prey.
Inside the slime mold, a rich soup of cellular components and food particles flows through the net. This flow transmits nutrients, chemical signals and information between different areas of the slime mold.
These undulating, stretching movements are probably what make slime molds so appealing and creepy to horror artists and filmmakers.
The physiology and anatomy of slime molds is as alien as it is fascinating. But it is their behavior that sets them apart from their peers and is perhaps too similar to ours to feel comfortable.
Far from being simple cells moving blindly across fallen leaves, slime molds can gather vast amounts of information from their environment and use it to make intelligent decisions about where to move and look for food.
Slime molds have been known to sense and move towards, and even away from, carbohydrates, proteins, amino acids, free nucleotides, volatile organic chemicals, salts, pH, light, humidity, and temperature.
When slime molds find multiple food sources at the same time, they try to cover each food with as much of themselves as possible (absorb it) without splitting into separate individuals. The most efficient way to do this is to have one tube connecting two products along the shortest path between them.
Slime molds have evolved over millions of years to become master network engineers. They are experts at solving mazes, and researchers have begun creating computer algorithms for designing human trains and telecommunications networks based on the slime mold approaches.
The ability of slime molds to solve problems is all the more fascinating because these creatures do not have a brain or even a single neuron. Yet they show signs of remembering and even learning, two things traditionally thought only possible in animals with brains.
When moving, slime molds leave behind a slimy trail that looks like mucus. This slime trail serves as an external memory of areas he has explored in the past, which is very useful for solving mazes.
They can distinguish between their own footprints, their neighbors’ footprints, and the footprints of other types of slime molds. They also use food signals left on tracks to estimate their own chances of finding food in the area.
The researchers also found that slime molds can learn to ignore substances they normally find repulsive (such as quinine or caffeine) after prolonged exposure. Researchers call this basic form of learning “habituation.”
Surprisingly, when an accustomed slime mold fuses with an unprepared slime mold (oh yes, they can do that), the newly merged individual exhibits learned behavior.
This all raises the (somewhat eerie) question: What other kinds of knowledge do slimy creatures pass on to each other as they crawl under the forest floor?
