Look beyond animals, plants, and even fungi, for a moment, and you’ll see a world made up of other, far stranger forms of life. Some of these organisms might look alien, such as slime moulds, but they originated here - on Earth - and play crucial roles in many ecosystems.
What are slime moulds?
While they may look a lot like fungi, and were once classified as such, slime moulds aren’t related to mushrooms at all. Instead, the term ‘slime mould’ refers to a variety of small to microscopic organisms that belong to many different groups, from Rhizaria to Amoebozoa.
Most slime moulds are terrestrial, living in damp, shady habitats underneath logs. They can be found globally and despite being at their most abundant in the tropics, a small number of species have been found in areas as dry as the Atacama Desert and as cold as the Arctic.
What do slime moulds do?
Often overlooked, slime moulds form an important part of soil ecosystems. By feeding on bacteria, fungi, and decaying organic matter, they release nutrients back into the soil that plants can use.
Like animals, slime moulds can move and actively hunt their ‘prey’. They do this by extending tendrils that, equipped with chemical receptors, are able to sense nearby food. They maximise their foraging efficiency by expanding outwards in all directions and leaving slimy trails of polysaccharides and proteins to remember places they’re already searched.
As slime moulds grow, they produce a colourful fruiting body that helps distinguish them from other species.
These fruiting bodies have inspired some unusual names, such as Dog Vomit Slime Mould (Fuligo septica), Wolf’s Milk (Lycogala epidendrum), and False Puffball (Enteridium lycoperdon).
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Are slime moulds really capable of learning?
Of the roughly 1000 species currently known to science, Physarum polycephalum is perhaps the most familiar, owing to its remarkable ability to learn.
This brainless microorganism is able to escape from traps, find its way around mazes, and even create elaborate transport networks that are more efficient than our own - which perhaps isn’t so shocking, depending on where you live.
In the early stages of its life cycle, P.polycephalum is a single-celled organism. However, as it grows it’s able to merge with others surrounding it, forming a larger organism that’s able to send out branches in search of food, such as fungal spores and bacteria.
These branches can grow up to one metre in length and, according to researchers, have some form of primitive memory.
In 2010, researchers from Japan’s University of Hokkaido set up an experiment where they placed porridge oats inside a petri dish containing P.polycephalum. These porridge oats represented railway stations and they were placed in a configuration that mirrored those around Tokyo.
The sample of P.polycephalum was left to do its thing and soon after it had created a copy of the Tokyo railway system, complete with all its branching routes.
Since then, slime moulds have mapped optimum transport networks for several cities, as well as a worldwide trade network. They’ve even been used to map dark matter throughout the universe and reveal connections in the vast cosmic web!
