The slime mould Physarum polycephalum is an intriguing and striking microorganism that exhibits simple “intelligence”. In this respect, it will move toward favourable, and away from hostile environments, can solve a maze in its search for food, and has a primitive memory. Here is some time-lapse footage which reveals a phenomenon akin to a microbial heartbeat.
Because we are drawn to the bright and the white, many of the commodities of our daily lives are manufactured to artificially express these properties, and in particular, to make them look cleaner or newer than they actually are. As a consequence of this, much of what we make contains synthetic compounds called optical brighteners. These chemical agents work by fluorescing, that is by absorbing natural (from the sun) or artificial (from standard lighting) ultraviolet light and converting it into other colours of visible blue light, to make objects appear whiter and brighter than they otherwise are. Optical brighteners are thus commonly found in our clothes, washing powders, and importantly here, paper. In these images the slime mould Physarum polycephalum has grown on paper and is observed under normal daylight and also under ultraviolet illumination. Under UV, the paper fluoresces a blue colour because of the optical brighteners in it, whilst the slime mould appears black. This is because it absorbs UV light. This might be a manifestation of a protective mechanism whereby it produces UV absorbing pigments which protects the organism against the damaging effects of sunlight. Such a pigment my offer a natural protective factor for suncream.
The slime mould Physarum polycephalum is a single-celled organism without an obvious nervous system. Nevertheless, it has recently been shown to use an external spatial memory to navigate. When it explores an environment, it leaves behind a trail of extracellular slime, which if it encounters later, it strongly avoids. This response ensures that the organism does not revisit areas that it has already investigated. The avoidance behaviour is also a choice because when no previously unexplored territory is available, the slime mould no longer avoids the slime. In essence then it possesses an externalised memory, which because it relies on feedback from chemicals, maybe a precursor to our own. I have developed a novel process that selectively reveals the slime mould’s external memory as it explores its environment. The blue-grey threads are the living organism itself which now occupies the routes where exploration resulted in success, that is, it found food sources. Remarkably, this “success” is surrounded by a matrix of failed possibility (the purple trails), that is the paths that the slime mould explored but that were never successful but which are still revealed by the unique process.