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By Carina Magyar in Nuisances —

VII: Lichen

Symbiotic partnership or toxic relationship?

septidi, the 17th of Pluviôse, Year CCXXXI
Close-up of lichen on a twig. Photo by Minna Autio / Unsplash

Good morning. Today is septidi, the 17th of Pluviôse, Year CCXXXI. We celebrate le lichen, a co-dependent relationship between fungus and algae.

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The word for lichen is relatively recent, having only been coined and assigned to the stuff 300 years ago. Prior to that, the word would sometimes be used to describe liverwort, a similar-looking moss. It comes from the Greek and means "to lick." The idea is that the moisture-attracting lichen gradually licks a rock away underneath itself, like an owl with a Tootsie Pop.

Lichen isn't one organism. It's two.

First, there's a fungus that has no root system, but absorbs water from the air and land around it. This gives it mobility, but no nutrition. That's where the algae (a short-hand term we're going to use for cyanobacteria) comes in. The fungus grabs tiny plant bits from whatever's handy nearby and takes it for a ride, using its chemical reactions to feed itself. In return, the algae gets a new habitat and plenty of chances to reproduce.

This is described as a symbiotic relationship, rather than a parasitic one, because the algae benefits. But just because it's symbiotic, that doesn't make it an equal one. The fungi clearly get the better part of the deal.

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VIII: Yew

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