An Ancient Fungus On A Fungus On A Fungus
by Elio
Sometimes the title says it all. Evidence of mycoparasitism and hypermycoparasitism in Early Cretaceous amber tells you: (a) that the authors are talking about something that took place some 100 million years ago, and (b) that there are several layers of parasitism in the specimen in question. So, what is this specimen in question? It turns out to be a mushroom encased in amber, currently the oldest known fossil mushroom (having bested the previous record holder, another mushroom preserved in amber).
Cap of a mushroom in amber named Palaeoagaracites antiquus covered with mycelium of a parasite, Mycetophagites atrebora. Bar = 0.5 mm. Source (Photo: George Poinar)
The authors could not identify the mushroom without getting into the specimen (find out below why they didn't), but it clearly resembles present day species (perhaps in the genus Mycena, Marasmius, or Collybia — mushrooms that are well known even to amateur mycologists). Pretty much all there is to this specimen is the cap, which is only 2.2 mm across. However, it is distinctly parasitized inside and out by a mycelium made up of the hyphae of some other fungus. This, in turn, is clearly parasitized by yet another fungus that invaded its tissue. The three fungi are readily distinguishable by morphological features of their hyphae.
Infection of fungi by other fungi (mycoparasitism) is widespread today, and may even have its uses for controlling unwanted fungal invaders of our crop plants. However, this seems to be the first known instance of triple-layered parasitism in the fungi. If it happened 100 million years ago, why not today?
Mycena corticola. Credit: Doug Stewart. Source
It isn't hard to imagine how this mushroom became encased in amber. At present, there are some tiny mushrooms that grow on the bark of trees. An example is the diminutive Mycena corticola which used to appear after every good rain on the bark of an English elm in my yard in Newton, Massachusetts. If a blob of resin were to fall on such a mushroom growing on conifers, the result may well be a specimen like the one we are talking about here.
Why not cut up the specimen for further study? One reason is that it was offered, intact, for auction on eBay. Asking price? $100K. No bids.
This must be near perfection for your mycophilia, Elio! It reminds me very much of the work of Raul Cano and his coworkers, who were able (they say) to isolate viable bacterial spores from ancient (megayears before present) amber. Or the folks who say that they have isolated living bacteria from crystals of halite many megayears old. Ah, but how do you prove the age—rather than just VERY slow growth in cracks of the amber over eons? Wiser heads than mine have debated this subject vigorously.
As for levels of parasitism, I will quote Jonathan Swift:
"So, naturalists observe, a flea
Hath smaller fleas that on him prey,
And these have smaller fleas to bite 'em,
And so proceed, ad infinitum."
‑Jonathan Swift, On Poetry: A Rhapsody (1733)
I'm sure that there are more than a few bacteria and even viruses involved in the mix! Every living thing is essentially an ecosystem to be exploited by other living things....
Great post!
Thanks, Mark. Your steadfast interest in this blog is greatly appreciated, especially because you always come up with challenging points (and also because you always have something nice to say). We intend to deal with aspects of paleomicrobiology such as the ones you mentioned. We already had a post on the cultivable bacteria in 120,000 old ice, but these are mere youngsters on the time scale you referred to (see http://schaechter.asmblog.org/schaechter/2007/04/old_small_cold.html)