NOTE: Correction below.
Well, this brings new meaning to the concept of gilled mushrooms. Scientists have stumbled upon the first mushroom that fruits underwater, as proudly displayed on the cover of this month’s Mycologia. Notice the little bubbles on the outside of the mushroom. On aquatic plants (like the moss to the left), bubbles form because the plant is producing oxygen via photosynthesis. On the mushroom, the bubbles are probably the product of respiration, which means they are filled with CO2, not O2, as the mushroom “breathes”.Yes, fungi burn sugar with oxygen to produce energy and CO2 just like we do, but you can see it here because the fungus is underwater*. Way cool! (CORRECTION: HeyPK points out in the comments that CO2 is highly soluble in water (true — at 20C in freshwater, the solubility limits are 1.45 g/L for CO2 vs. 9 mg/L for O2) so the bubbles are more likely more oxygen bubbling out of the supersaturated stream using the mushroom as a substrate much the way the CO2 in carbonated beverages comes out of solution on ice in glasses. Oops! Sorry for the mistake readers — I’m still learning too. I’m sure I’ll make more from time to time despite my best efforts so please do help me fix them when you see them and I will post a prompt correction. : ) )
According to the good folk over at MycoRant, where I discovered this, scientists had never looked for mushrooms underwater before, but that didn’t mean they weren’t there. Brit Bunyard, editor of Fungi, speculates there may be a whole world of aquatic mushrooms out there we didn’t know about because we never really looked. If so, he noted at MycoRant, it would not be the first time that happened.
The mycologist Cecil Terence Ingold (who as of last year was still alive at the age of 104) stumbled upon an entire world of virtually undescribed fungi living in ephemeral forest pools and trickling streams:
In 1937 Ingold moved to University College, Leicester, where he “became excited by the chytrids attacking planktonic algae”. It was his discovery of one particularly beautiful such chytrid (Endocoenobium eudorinae) that reportedly caused him to specialize thereafter in mycology rather than plant physiology; and the next year, while searching for chytrids in a small brook near his home, he found in the stream scum an “abundance [of] many kinds of most extraordinary fungal spores”, most of which were large and tetraradiate in shape. For several months he continued to find such spores in scum, and he finally discovered their source to be fungi living on submerged alder leaves in the stream bed. He later learned that a few such fungi had been described earlier, but, he thought, “rather inadequately”; and so he undertook to classify those aquatic hyphomycetes into eight new genera, all of which remain valid today.
They are sometimes called the “Ingoldian Fungi” in his honor. The incredibly beautiful spores of these fungi (often called amphibious or aero-aquatic fungi or aquatic hyphomycetes), in addition to being star-shaped, whorled, knobbed, or otherwise tricked out in the most wonderful fashion, are hollow when found in still pools — so they can float and get first crack at the ecosystem’s power source: leaves that have just dropped to the water’s surface.
Dear readers, there’s a whole crazy world of living things out there, often invisible to the naked eye but fabulous beyond belief, even in an otherwise unexciting-looking puddle in the forest outside your door. All we have to do is look.
*And by the way, the gills in mushrooms are for maximizing the spore-making surface area, not for maximizing the gas-exchange surface. Most mushrooms are small enough the CO2 just diffuses out passively (giant puffballs notwithstanding).