February 18, 2012 | 1
This article is the fourth (see the first, second and third articles here) in a miniseries of six articles (yes, I added one) that will be posted over six days about civilization, fungus, and alcohol. The first four articles are already determined, but just how this series finishes up will be chosen by the comments and ideas of readers.
Several years ago my friend Kenji Matsuura discovered termites balls. Now, along with his student, he has published a new study revealing a bit more of what long lay hidden.
I should explain. What Kenji discovered were tiny, hard, round, egg-shaped fungal structures inside termite nests. The fungi were there to steal rotting food from the termites. They did so by mimicking the eggs of the termites (which involved producing hardened sclerotia composed of fungal hyphae)1. The termite balls were the exact width and even firmness of termite eggs; they were just like mother makes. The fungal balls resembled the termite eggs, but they also produced a chemical the termites use to recognize the eggs, lysozyme. This subterfuge is elegant and, it turns out, common. It occurs in termite species all over Japan, but also in the United States. It might be occurring in your house.
New Discovery–These balls were named by Kenji because of their physical resemblance to soccer balls or basketballs. Kenji has come to see these egg-shaped fungal structures as a great mystery in need of explanation and so has dedicated much of the last ten years of his life to their study. Kenji is incredibly clever. He could have done anything with his life, but he loves termites and now termite balls. He may well be involved in every study of termite balls ever published. Now, Kenji, in a paper led by his student Toshi Yashiro—like Kenji a very clever young scientist (though a terrible driver)—reports on new details of the relationship between the termites and these fungal cheats.
[Image 1: Termite eggs (long, translucent shapes) and their mimics, termite balls in a species of Reticulitermes termites, photo by Alex Wild]
Yashiro, Matsurra and one of Matsurra’s postdocs, Tanaka, studied termite balls all over Japan as well as in the United States. They lifted termites carefully and looked all through their nests. As they searched, they became experts in their quarry. They then came back to the lab and compared the versions of the genes of the termite balls (all species of the fungus genus Fibularhizoctonia) in different termite nests. What they might have expected to find is different fungus species in each termite species, at least if specific adaptations were required to deal with the unique chemistry of different termites. Instead, different termite species seemed to have different termite ball species and individual nests often had more than one species of termite ball dependent upon them.
Playing the fool–It seems as though many different fungi can trick many different termite species, using lysozyme (Matsuura can paint the lysozyme on glass beads and the termites will care for them too). That, along with a vague resemblance to an egg is enough. The termites are easy. It is a small wonder more species don’t trick them. They remind me of humans, a point to which I will return.
Once in the termite nest, the fungi have it made. The termites take care of them as if they were their own real eggs. They clean them (see movie here). They move them to the best spots. They are either the best hosts in the world or the worst parents. In some nests, more of the “eggs” being cared for in the nest are termite balls than actual eggs. Based in part on Yashiro’s new work, these fungi appear to be able to get nest to nest and even reproduce on their own outside nests, but they like the free ride they can get inside a nest. Its cheap and easy living when the world outside is rough.
From a distance, it seems the termites are being had, but measuring who is winning and who is losing is complex. When Matsuura compared the fitness of termite eggs in nests with termite balls to those without, the termite eggs actually do as well when the termite balls are present. But there must be a cost to workers of tending so many extra “eggs.” Maybe there is also a benefit. Maybe this Trojan ball had a silver lining. Perhaps compounds produced by the fungus work as an antibiotic and, in doing so, help the young termites to stay pathogen free. The termites may benefit from being duped, but the benefit seems incidental, not a reason to let the fungus in, but perhaps the reason stronger defenses against the fungus never evolved.
Matsuura has big ideas for what is next. He would like to try to take advantage of the termite’s graciousness (or lack of guile) to kill them. As Matsuura put it in a recent paper, “Dummy eggs filled with pesticides could be introduced into the royal centre of a colony, destroying the entire colony with only a small amount of pesticide.” The truth is, Matsuura doesn’t really want to kill termites. He likes them, but you don’t get grants for liking termites, you get grants for killing them.
In and of itself, this story is fascinating, a rich detail of the natural world that would be inconceivable had evolution not already conceived it. But, in the context of the story of humans and alcohol this story seems like something a little more.
If the termites were to tell their own story, much as we tell our own story when we write about alcohol, what would they say? They might describe the day they brought in the termite balls into their nests as a noble and useful one, a day in which they figured out how to harness fungi in order to control pathogens, much in the way in the last article I described the benefits of alcohol. But it seems clear enough the termites are being tricked.
What if yeast, that fungus that makes our beer, wine, bread and more, is tricking us? What if, in looking to the yeast, we are able to convince ourselves of its benefits, but from the yeasts perspective, we are just another dumb termite? After all, don’t we bring it in out the wild, make sure it is safe and fed and help it from one food source to the next, always sure to keep it neither too hot or too cold. What if that is the story of alcohol, fungus and civilization, a story in which we feel good about ourselves but are not really in control?
[Image 2: Termites of a species of the genus Nasutitermes. The soldiers of these termites have long "nose-cannons" out of which they expel turpentine-like compounds in defense, photo by Alex Wild]
Repeat–Recently, Matsuura and Yashiro made one more discovery. In studying a tropical termite of the genus Nasutitermes they found giant termite balls. These giant termite balls were totally unrelated to normal termite balls. They had evolved independently to take advantage of the termites predictable weakness. The giant termite balls are, as their name suggests, larger than the normal termite balls, probably because the eggs of Nasutitermes species are larger than those of Reticulitermes termites and so the fungus must follow suit. These larger balls beg the question. They beg the question of what our predictable weakness is, if we have one. In the context of the beer and wine made by our yeast, the answer that seems most obvious is that our predictable weakness is we like to drink. Maybe yeast first prospered by sneaking into our societies in the guise of a Trojan beer. That we wanted to get drunk and kill pathogens meant we let down our guard and now, for as long as our weakness remains alcohol, they are in.
Table of evolutionary contents: Here you can skip ahead or backward to the other chapters in the story of the other species in our daily lives, whether they bethe cow, the chicken, the hamster, bacteria (on Lady Gaga, on feet, in bathrooms,as influenced by antimicrobial wipes, as probiotics, in the appendix), pigeons and urban gardens, house sparrows (to be published next week, stay tuned), predators,diseases, dust mites, basement dwellers, lice, field mice, viruses, yeast, the fungus that produces penicillin, bedbugs, houseflies, or something more.
Or for the big picture of how Rob thinks these stories come together to make us who and who we are, check out The Wild Life of Our Bodies. Rob Dunn is a writer and evolutionary biologist in the Department of Biology at North Carolina State University. Find him on twitter at robrdunn. Find him in person somewhere in Europe with his family while they are all on sabbatical.
1-Matsuura K., Tanaka C. and Nishida T. 2000. Symbiosis of a termite and a sclerotium-forming fungus: sclerotia mimic termite eggs. Ecol. Res. 15: 405-414