Slime moulds – a collection of organisms that closely resemble amoebae – have for years eluded scientists. The single-celled microorganisms can think, yet have no brain. They can remember without having experienced it.
Slime moulds have built entire networks incomprehensible to humans – in 2010, a slime mould revamped the entire Tokyo subway system to make it more efficient.
Most slime moulds live out their lives as micro-organisms invisible to the naked eye.
When they produce, however, they can scale up in size to form fruiting bodies.
Also known as “sporangia”, these bodies release spores into the wind in a way that parallels fungi, spreading their seed in every direction, and so beginning a new cycle of life.
As Jules Howard explained in a BBC Science Focus piece, slime moulds can be found the world over, usually in woods, in dead trees, or in soil.
To scientists, the so-called “plasmodial” slime moulds have proved the most interesting.
By continually replicating their genetic material without dividing into new cells, species of this group can stretch and become a giant super-cell organism more than 10 metres in size.
Slime mould expert at the Centre for Integrative Biology in Toulouse, Dr Audrey Dussutour, says it’s at the plasmodial stage that slime moulds are best described as a “blob”.
When the slime mould is exposed to an external stimulus – for example, caffeine or salt – it usually focuses its growth on aspects not related to its task.
However, the study showed that overtime, if P.polycephalum discovers it can reach a food source by travelling through the stimulus, it learns to focus and keep going to get its reward.
It is able to adapt comparably quickly, and share this knowledge with other slime moulds that haven’t encountered the risk by fusing together.
Perhaps most interestingly, the slime mould is able to retain this information even if it goes into hibernation for weeks.
Dr Dussutour said: “Slime moulds illustrate that even simple organisms can exhibit behaviours usually encountered in animals with brains.
“They encourage us to take another look at single-celled organisms.”
P. polycephalum’s ability to seek out food has piqued the interest of the engineering industry, including transport and town planners.
The slime mould’s simple methodology of finding the most efficient route to food has also found itself within the circles of cosmologists.
Algorithms generated by observing the ways slime moulds grow connections between food sources have proved a useful way of studying how dark matter connects galaxies.
There are around 900 known species of slime mould.
However, hundreds, perhaps thousands more wait to be discovered.