A touch of light: intriguing slime mould

13 April 2021

2716

By MIKE GILLAM

Photos © Mike Gillam

My last story lured me into a labyrinth of scientific papers, YouTube films and TED talks, describing the complex and little known nature of mushrooms, puff balls, truffles, toadstools, sponge coral, rust and smut fungi and the processes of decomposition, of mycorrhizae and the role of mycelia, rhizomorphs and hyphae.

One article unveiled the subterranean marvel of the “largest organism on earth”, thought to be a specific honey fungus, a clonal colony of Armillaria solidipes measuring 3.8 km across, recorded in the Blue Mountains of Oregon. Researchers calculated that the colony covered an area of 9.6 sq km, and was somewhere between 1,900 and 8,650 years old.

There are so many facets to fungi, a field where my knowledge is seriously lacking that I went in search of a specialist I once knew for help with identifications and to clarify some facts. This proved quite difficult because I don’t do Facebook, LinkedIn or other social media. Sadly, my basic social networks proved much less efficient than the subterranean mycelial networks employed by fungi.

As the Alice Springs News deadline passed I was no closer to locating mycologist (fungi aficionado) Arpad Kalotas. Out of options, I sensibly cut the draft in half and posted the story which was too long anyway.

I returned to the subject when I received an alert from Charlie Carter regarding an unusual fungal like structure that appeared in his garden. My first fungi story was carefully timed for our wonderfully wet autumn when surface formations often appear and it’s gratifying to report they have met my expectations.

My newfound enthusiasm for a fungi follow up was promptly derailed when Charlie’s spectacular life form, on closer inspection, was revealed to be an imposter. Slime mould belongs to the separate kingdom of Protista (Protoctista). Or is it Amoeba? Confusion seems to persist about their rightful position in the tree of life but it’s definitely not a member of the Fungi kingdom.

Their occasionally strong resemblance to fungi is superficial. Slime moulds are in fact single celled organisms that can contain millions of nuclei. Unlike fungi they move/pulsate (slowly) in their quest for food and also lack chitin in the composition of their cell walls. Charlie’s specimen has the texture of an aquatic sponge and resembles a species called dog vomit slime mould.

The frequent proclamation that fungi are closer to animals than plants is partly based on the presence of chitin, a fibrous substance enabling the formation of rigid cell walls in fungi and a strong and flexible exoskeleton in arthropods.

Incidentally, researchers who revealed the intriguing problem-solving abilities of slime mould in moving through a maze and creating foraging pathways that bore some resemblance to a map of the Tokyo area railway system were recognised by Ig Nobel Prizes in both 2008 and 2010.

These awards “honor achievements that make people LAUGH, then THINK. The prizes are intended to celebrate the unusual, honor the imaginative — and spur people’s interest in science, medicine, and technology.” I can also recommend this short YouTube film on the behaviour of slime mould.

While some species of fungi and probably slime moulds are bioluminescent, I missed the opportunity to see if Charlie’s specimen actually glowed in the dark. It was however a spectacular fluro yellow in colour, and I’m sure it ‘glowed’ at least subtly in the moonlight against a backdrop of dark leaves and woodland litter.

There was a new entity on the surface each morning over the space of a week and doubtless even greater movement beneath the conspicuous and colourful fruiting bodies. I photographed the bright yellow example (at top and above left) noting its amazing rate of growth: approximately 70mm x 45mm overnight. I was reminded of an amazing fungi story from the western Australian goldfields.

The discovery, which made news around the world, was revealed by Australia’s national science agency, CSIRO, and published in the journal Nature Communications:

“The thread-like fungi attach gold to their strands by dissolving and precipitating particles from their surroundings, in a process that could offer clues for finding new gold deposits. There may be a biological advantage in doing so too, as the gold-coated fungi were found to grow larger and spread faster than those that don’t interact with gold and play a central role in a biodiverse soil community … Fungi are well-known for playing an essential role in the degradation and recycling of organic material, such as leaves and bark, as well as for the cycling of other metals, including aluminium, iron, manganese and calcium…”

In the early 1980s I was fortunate to travel with Arpad Kalotas who worked for a time in Central Australia. We were passing through an area of huge termite mounds, Nasutitermes, that occur on the margins of ancient paleo drainages when my colleague pointed to a tall white fungus growing from the summit of a termite mound. Unexpected and slightly ridiculous, the visible fruiting body was an impressive size, although of course this was the surface expression of something larger thriving in the heart of the three-metre tall mound that boasted abundant shade and humidity.

Arpad mentioned this stalked puffball only occurred in close association with termite mounds. So clearly the social insects are cultivating the fungi to break down the cellulose of indigestible materials and in return the developing fungi nodules provide food for the termite colony.

Decades later I stopped to photograph this fine example of Podaxis beringamensis protruding from a giant termite mound in the Tanami Desert (above left).