Let’s talk about sex baby . . .
By Daniel Butler, author and forager
Let’s be clear: we’re not addressing the fumbling, mucky, animal stuff, nor those boring passive plant processes – we’re talking about mushrooms. And yet again, Britain’s myo-ignorance is on full display. As a nation we badly need a sex education lesson.
Now most people realise fungal reproduction revolves around spores, but after this the understanding peters out. These are usually thought of as microscopic seeds, but this is so crude a simplification as to be deeply misleading. Apart from being the means of disseminating a new generation, spores are very, very, different.
This print from a cultivated mushroom is made by millions of spores
(Image: Author’s own)
A plant seed is a miniature survival capsule, packed with nutrients and energy. They contain almost all of the starting blocks required for a new plant. The drawback with this is that each consumes precious reserves. This severely limits production.
In contrast microscopic fungal spores contain little more than basic DNA. This means even a tiny mushroom can produce them in the millions. When these land in a suitable substrate these produce thin, hair-like hyphae, each cell of which contains a single nucleus. When one hypha grows close to another they fuse. Thereafter each cell contains two nuclei. If conditions are right - such as a change in temperature - a fruiting body (mushroom) forms and the two nuclei fuse, re-sort the chromosomes and divide to produce new spores.
A cursory glance shows the incredible inefficiency of this form of reproduction. Each mycelium can live for many years and every season it will produce dozens or even hundreds, of mushrooms, each bearing millions of spores. Thus over its lifetime, the fungus can generate many billions spores. Like all living things, the survival of the species depends on each mycelium replicating itself just once over the course of its lifetime. In other words, a fungus which produces trillions of spores only has to get lucky once.
Low-growing mushrooms such as these fairy rings struggle to spread their spores
(Image: Author’s own)
One reason for the inefficiency is that most species rely on wind to disseminate their spores – and many grow in habitats where this is in short supply – for example when they fruit close to the ground. But there are ways to get around the limitations. One is to release spores from the top of the cap rather than simply drop them. Puffballs, for example, split to allow gusts to snort the powdery contents into the atmosphere. Another is to go for sheer volume. Big porcini, for example, can weigh well over a kilo with possibly a quarter of this devoted to the production of tens of millions of spores.
Some seek altitude to improve their chances. For example chicken of the woods bursts from the trunks of veteran trees. But the most ingenious manner of gaining altitude has to be that of the Cordyceps family. These parasitise insects, usually entering their victims via the trachaea (microscopic breathing holes on the abdomen). As the ant or caterpillar chews its plant matter, so the fungus is feasting on their host’s internal organs. It then sends out a chemical message which forces the insect to leave cover and venture into the open. Once exposed to the elements the fungus kills its host by exploding one or more mushrooms through its body or brain.
Stinkhorns harness flying insects
(Image: Author’s own)
On a more prosaic level the stinkhorn (Phallus impudicus) fruits to resemble an erection with a smelly green, brown or black tip, Flies land on this believing it to be a choice morsel of rotting flesh and when they depart it is with feet covered with sticky spores.
Pigs are driven to seek out truffles
(Image: Author’s own)
The biggest challenge of all, however, faces subterranean fungi. Most notable are truffles which exude strong aromas to attract animals. The edible species which are most valued by humans give off chemicals which mimic the pheromone androstenol. This is a natural wild boar aphrodisiac and other swine are drawn to dig it up and wolf it down, for the spores to be dropped several hours later in another part of the forest. Now we share many physiological traits with pigs which might explain why these prized fungi have long been associated with human lust and sex.