Fungi are one of the most diverse and omnipresent forms of life. There are likely millions of species, the vast majority of which are unidentified and poorly understood, performing all kinds of crazy ecological roles we haven’t even begun to study. But they do have one limitation: mushrooms don’t grow underwater, right?
You won’t see marine mushrooms in field guides, and might never encounter one with your own eyes, but they do in fact exist. According to Wikipedia, 400 species of marine fungi have been described. This is thought to represent something like 1% of the total number of marine fungi.
But fungi and mushrooms aren’t quite the same thing. Mushrooms are specifically macroscopic fungi, you might point out. Sure, there might be all kinds of microscopic fungi, but “real” mushrooms underwater??
The answer is still yes, although this is very uncharted territory. The best described, and possibly only fully accepted underwater mushroom is Psathyrella aquatica, which was first documented in Oregon in 2005. For more information on this mushroom see the sources below.
The existence of underwater mushrooms poses further questions. Fungi respire, so how does an underwater mushroom “breathe”? One suggestion is that P. aquatica creates a bubble around its gills that allows for gas exchange and spore release. Other aquatic fungi are believed to absorb oxygen directly from the surrounding water in the same way that fish do through their gills.
Another question is, how does spore dispersal work? Wouldn’t all the spores just float downstream and out to the ocean? This question remains to be definitely answered, but it seems likely that aquatic insects are involved. Perhaps aquatic insects lay their eggs in the mushroom which then covers the larvae in spores?
Another remarkable thing is the fact that this mushroom must have evolved from terrestrial mushrooms, as opposed to evolving directly from marine fungi, because it’s a member of the genus Psathyrella, which is an extremely common group of terrestrial little brown mushrooms. Interestingly, the first fungi were aquatic. They are believed to have lived in water and swam around using flagella. Psathyrella aquatica‘s ancestors then colonized the land some 500 million years ago, only for it to recolonize water.
I have a vague memory of having seen something like a mushroom underwater. Most likely this is retroactive thinking, but now that we know to look, who knows what we will find?
Sources:
recycled paper clips 