Secret of mushroom shape revealed

By Jody Bourton
Earth News reporter

Ready to reproduce

Scientists have worked out just what a perfectly designed gill mushroom would look like.

Their study reveals that no such fungi exists naturally, but it does show how a mushroom's unique structure helps it reproduce so successfully.

The research also sheds light on why different mushrooms possess different arrangements of fleshy gills underneath their caps.

The findings are published in the journal Mycological Research.

Mushrooms are fruiting bodies produced by fungi, and they grow to spread reproductive spores into the environment.

Mushrooms are masterpieces of natural engineering Professor Nicholas Money Miami University, Oxford, Ohio, US

For over a century, mycologists have studied fungi structure, and it has long been known that the soft filamentous structures called gills found on the underside of many capped mushrooms help spread spores.

"Spores are catapulted from the gill surface, travel a short distance horizontally, and then fall vertically to be swept away by air currents swirling around the mushroom cap," explains Professor Nicholas Money from Miami University, Oxford, Ohio, in the US.

The spores then start new fungal communities.

But only now have researchers revealed the perfect shape for a mushroom's fleshy gills.

Prof Money and Dr Mark Fischer from the College of St Joseph, Cincinnati, also in Ohio, US used theoretical modelling, measurements and photographs to investigate the optimal gill structure for a mushroom.

Natural gills fork, aiding spore dispersal

"We set out to design the perfect mushroom," Prof Money says.

In nature, gilled mushrooms have gills arranged so that they fork and branch off.

By having this arrangement relative to a flat surface the mushrooms are able to increase their surface area 20-fold and increase their spore dispersal, the researchers say.

"Mushrooms are masterpieces of natural engineering," says Prof Money.

But no mushroom in nature has an optimal design.

Grand design

"We found that the most efficient arrangements in engineering terms do not occur in nature."

"A single gill organised as a tight spiral beneath the cap would work very well, and a 'venetian blind' type arrangement would be very effective too," he says.

A hypothetical 'spiral' mushroom with one long gill spiralling to the centre.

But neither optimal arrangement occurs naturally, due to the constraints imposed by how a fruiting body develops.

For a start, the arrangement of cells requires each mushroom to develop radial symmetry.

"Natural selection has sculpted various radial arrays of gills that work very well, or at least, work well enough to have allowed mushrooms to flourish for tens of millions of years," says Prof Money.

By increasing its surface area 20-fold, a mushroom could increase the number of spores it releases by the same amount.

"Twenty billion spores is a lot more than 1 billion spores," says Prof Money.

Design by nature

Scientists are interested in how natural structures such as those found in mushrooms may be used to inform engineering designs.

A hypothetical "Venetian blind" mushroom with gills arranged in lines .

"There might be some ways in which the arrangements of gills in a mushroom could aid the design of heating or air-conditioning devices, or filters for purifying water," says Prof Money.

The next challenge for the researchers is figuring out what kind of mushroom is the most efficient at releasing spores.

"We are going to start by looking at bracket fungi next, these have fruit-bodies that release spores from skinny tubes rather than gills," Prof Money says.

Preliminary studies indicate that bracket fungi can increase the surface area for spore release by a factor of 40 or more.

"The storm of spores falling from these giant brackets is a truly amazing sight and well worth an evening trek into the woods," he says.