Long admired for their active and cooperative community behavior, some types of ants also wear a gardening hat. Nurturing underground fungus gardens, these ants have a win-win relationship that provides food for both ants and fungi. If we humans understand it better, it may just help us out, too.
Several types of ant species live in mutual relationships with fungi. The best-known farmer ants are leafcutter ants which defoliate significant quantities of vegetation to feed their particular fungus.
Yes — the fungus eat the greens, then the ants eat the compounds created after the fungus has digested its salad. Ants do not digest leaves well, but happily for them, their fungi do. The daily life of a leafcutter involves a lot of leaf cutting.
Another species of ant that farms fungus are called Sericomyrmex. A recent paper from the Ant Lab at the Smithsonian Institute revises and clarifies our understanding of this fungus-farming ant group, and along the way, discovered a new type of ant, among other things. Sericomyrmex ants are known as "silky" ants because their bodies are covered with long hairs that give them a sleek, "velvety" look.
Published in ZooKeys, the revised taxonomy used DNA sequencing and analysis to update morphological qualities of the Sericomyrmex genus. Morphological refers to the specific structure of a thing, whether it be an ant, a butterfly, or a word. In this case, study authors recorded 18 standard measurements of the types of ants that belong to this family, including 529 workers, 50 queens, and 39 males.
Ants have been farming a lot longer than humans. Of approximately 119 total species of ants, 78 farm fungus in one form or another, and they have been doing it for about 60 million years.
Within the many families of ants that grow fungus for food, there are two groups; There are "lower" order ant species that grow fungus for the byproducts they produce, but the fungus could also live outside the ant colony in a different setting. A "higher" order farm ant cultivates a type of fungus that is so specialized that it lives nowhere else except in the unique conditions provided for it by ants in their gardens.
While you might be cultivating some fungus on food in your refrigerator right now, chances are good you are not doing it on purpose. For ants, fungal gardens offer nutrition they could not otherwise provide for themselves.
Unlike leafcutter ants, Sericomyrmex ants bring home fallen and decaying plant material, insect bodies, old flowers, and feces for their fungal garden. The symbiotic fungi tended by ants decompose the material into food for ant larvae and older ants. Like human farmers, these ants work hard to create balanced growing conditions for their crop. Digging chambers beneath ground let the ants control moisture and airflow.
Fungus-farming ants are of significant interest to medical science. Over millions of years, many of these ant species evolved to produce or nurture beneficial bacteria to protect their fungus gardens from parasitic microbes. Research initiatives are underway to explore the capabilities of compounds produced through the insect-fungus relationship, in hopes of creating useful antibacterial or antifungal drugs of use to humans.
While looking closely at the features of Sericomyrmex ants, the Smithsonian researchers made three discoveries. The first is that these fungus-farming ants don't have the same beneficial bacteria that their fellow fungus farmers possess. Despite this, their fungal gardens are free from parasites.
Second, as researchers looked more closely, they were surprised to notice the bodies of these ants are covered in what authors describe as a "white, crystal-like" layer.
The study wonders if this crystal-matrix could be microbial and offer similar protections to the ant and its fungus that beneficial bacteria do for other fungus-farming ants. Future studies will look at the role this layer might play in protecting ants or fungus. Alternatively, the layer by itself may offer structural protections. These are important questions that may yield real benefits to humans if the matrix provides some form of antimicrobial capability.
And the third discovery? While updating the knowledge base on this ant species, the researchers discovered three new types of ant in this family. One of the species was collected in the Venezuelan Amazon, and the scientists named it Sericomyrmex radioheadi, after the British musical group Radiohead. In the taxonomy, the authors explain why they chose the name:
This species is named after the English rock band Radiohead as an acknowledgement of their longstanding efforts in environmental activism, especially in raising climate-change awareness, and in honor of their music, which is an excellent companion during long hours at the microscope while conducting taxonomic revisions of ants.