by Janet Spencer

Instead of seeds, mushrooms produce spores, which are almost as fine as smoke. Most fungal spores are single cells. Mushrooms also reproduce by sending out their thread-like “roots” called mycelium, but that method is very limited, whereas spores can spread very far, very fast. Come along with Tidbits as we consider spores!

THE RAINY SEASON

The spores of mushrooms are made of chitin, which is the hardest naturally-made substance on earth. Chitin also forms the exoskeletons of insects and crustaceans, the beaks of the octopus and squid, and the tongue of mollusks. Researchers speculate that mushroom spores may be capable of surviving space travel.

• Spores have thick walls, preventing them from drying out. Their typically dark coloration protects them from the damaging ultraviolet rays of the sun. Their exteriors tend to be spikey, making it easy for numbers of them to clump together.

DISPERSAL METHODS

One type of stinkhorn mushroom in Australia emits an odor that attracts flies. When the flies arrive, they find a yummy oily substance which they eat. It also sticks to their feet. It’s packed with spores, which are then widely distributed as the fly flies around.

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Some species of tropical orchids perfectly mimic the smell, shape, and color of mushrooms in order to attract mushroom-loving flies to do their pollination.

• A type of fungi that lives in dung will “throw” its spore-laden cap. On a rainy day, the fungus absorbs water, swelling in size, and increasing the pressure in a stalk that ends in a cap. When it reaches maximum pressure, the cap of the stalk pops off, landing up to 18 feet (5.5 m) away. It lands on a piece of grass, where it seals themselves to the vegetation using a type of slime that dries and glues them in place.    At some point, the grass with the spore will be eaten by a passing creature. The spore-filled cap flows through the digestive track unharmed, and lands in a fresh new pile of dung far away from the parent colony.

• In a similar method, a type of fungus that grows on dung forms a small oil-filled chamber similar to a lens. The oil is packed with spores. The fungus pressurizes this chamber to about the same pressure as a truck tire. When the chamber finally bursts, it squirts the spore-filled goo up to ten feet away – always in the direction of the greatest amount of light. The goopy blob hopefully lands on a blade of grass, where it stays glued in place until eaten by a deer, cow, horse, or sheep and carried away.

• Many species of fungus spread their spores by storing them in a cup-like structure where the wind picks them up like blowing out a candle and carries them away.

• One fungus uses water for dispersal. The spore packets are shaped like tiny flasks. The thick end of the flasks is embedded in small pits in tree bark, with only the neck of the flask peeking out. When it rains, the flask swells in size, the neck sticks out farther, and it begins oozing spores. Rain drops carry the spores downward.

The ambrosia beetle lives at the base of trees and feeds exclusively on the ambrosia fungus. It trundles about the forest floor, and when it finds that fungus, it brings spores back to its home tree and plants the spores there, cultivating its own garden of the fungus so it always has something to eat. It collects the spores in a little “basket” on its exoskeleton. A rival species of beetle also lives in the tree, and steals the ambrosia fungus. This species is unable to cultivate its own garden because it has no “basket.” The relationship benefits both the beetle and the fungus, but harms the tree. The ambrosia beetle is native to South East Asia and made its way to the U.S. in packing material, bringing the fungus with it. The fungus has spread across the eastern U.S., causing a disease known as “laurel wilt” that kills members of the laurel family.

• The bird’s nest fungus sits on decaying wood and produces tiny packets of spores that look like little eggs, sitting inside upturned cups that look like nests. Each “nest” is only a third of an inch long, and contains about ten “eggs.” When a raindrop hits the nest, one or more of the egg-like spore packets travels with the rainwater as it drops to the forest floor, trailing a sticky filament. The filament wraps around a twig or leaf on the forest floor, anchoring the spore packet in place. The weather eventually wears away the surface of the packet, releasing the spores to the wind.   

SPORES BY THE NUMBERS

A fungus known as “smut” that affects corn can produce about 25 billion spores for each ear of corn. The fungus that causes stem rust in wheat generates about 10 billion spores per acre of wheat.

• One type of wood decay fungus produces spores at the rate of 350,000 per second for up to six months per year, for up to ten years before dying of old age.

In completely still air, a spore will descend at the rate of 7 feet (2 m) per minute. However, due to their tiny size, they can be lofted on the wind where they can stay airborne for long periods of time, travelling great distances.

• One researcher did an experiment on spore dispersal, releasing harmless spores on the first floor of his office building just to track their movement. Within five minutes, the spores had wafted to the 4th floor, and five minutes after that they were falling to the floor of the 4th floor at the rate of thousands per square yard.    Air samples taken at Arctic stations show a huge number of spores, in spite of being thousands of miles away from the nearest source.   

• One research station on the edge of Paris in 1879 measured the spore count of the atmosphere at different times and conditions using sticky slides exposed to air currents. It was found that the airborne load of fungus spores decreased greatly during heavy rain but rebounded up to tenfold after the rain.

WORD ORIGINS

The German “smotzen” means “to make dirty” and gives us the word “smut” which now refers not only to the moldy mildew that ruins crops, but also to unsavory items. The word “smudge” also springs from this source.

• The word “mushroom” comes from the French word “mousseron” meaning moss.

• The word “fungus” comes from the Greek word (which comes from the Latin word) “sphongos” meaning “sponge.”

• The Old Norse word “mold” referred to dirt or soil.

• The Greek word “khitōn” meaning mollusk, gives us the word “chitin” which is something with an impenetrable shell like a mollusk.

The Latin “spora” meaning “to sow” gives us “spore.”