Thriller Growths on Termites Result in Main Assessment of Ectoparasitic Fungi

Spore-producing structures vary widely among the fungi that infest termites. The structures at right show some of the variety in structures within the fungal genus Laboulbenia, which infests termites in the genus Macrotermes. A new report in the Annals of the Entomological Society of America details 34 species of fungi that specialize in parasitizing termites. (Image courtesy of Megan Wilson, Ph.D.)

By Leslie Mertz, Ph.D.

Leslie Mertz, Ph.D.

After spending a couple of weeks on an entomological expedition to the lush tropical forests of Guyana in northeastern South America, researchers had collected a variety of dragonflies, ants, and termites they could study when they returned to their labs at Rutgers University and the American Museum of Natural History (AMNH). Little did they know that something else was hiding among their specimens.

The “something else” was a set of mysterious growths on the underside of a few termites in the genus Amitermes. “Of the 50-plus species of termites we collected and preserved from that trip to Guyana, we found the growths in only one colony, and, of the approximately 200 members we collected in that colony, they were only on seven individuals,” says Megan Wilson, Ph.D., a student in the biology department at Rutgers University and graduate researcher at the American Museum of Natural History. “The interesting thing was that the growths formed fixed pads on the belly of each of these termites, and the pads were arranged in pairs of six, so each abdominal segment had two lesions that were almost completely symmetrical. We didn’t know what it was at all and, at one point, were even thinking it might be part of the termite.”

Playing Detective

Entomologists Jessica Ware, Ph.D. (left), and Megan Wilson, Ph.D., collect termites from a mound in in a flood-zone region along the Rupununi river region in Guyana, South America. Of the 200 individuals they collected from this mound, they discovered that seven had nearly identical mysterious growths on their undersides. That finding led to a months-long quest to determine the origin of the growths and a subsequent review article exploring fungal–termite associations. (Photo courtesy of Megan Wilson, Ph.D.)

Months of detective work followed, including literature searches to piece together information from decades-old and difficult-to-find scientific papers, many of which were in French, Italian, or Latin. “We found out eventually that it’s actually a really weird way that a fungus is presenting itself,” Wilson says. In particular, it was a termite-specific, ectoparasitic fungus in the genus Termitaria. It appears to be a new species, which the researchers have tentatively named Termitaria hexasporodochia.

On the path toward identifying the furtive hitchhiking fungus, Wilson not only learned a lot about fungus herself, but she also decided to expand her knowledge and, at the same time, make life easier for the next researchers to come along. The result of that endeavor is a new review article on ectoparasitic fungi associated with termites, published last week in the Annals of the Entomological Society of America. Wilson is the lead author, and coauthors are entomologist Jessica Ware, Ph.D., of AMNH (previously of Rutgers) and biologist Phillip Barden, Ph.D., of the New Jersey Institute of Technology and AMNH.

For the review article, Wilson set out to find everything known about the 34 species of ectoparasitic fungi of all the termite species they had collected in Guyana. A 1986 Mycotaxon paper (“Biogeography of Fungal Ectoparasites of Termites”) put her on the right track, and she branched out from there. “I started going through research papers, reading them all, searching through all the references, and just kept digging and digging to find every paper so I wouldn’t miss anything. Oh, the poor librarians! Every day I was requesting articles on these super-specific termite fungi,” she recalls with a laugh. After that, she pulled it all together into a review that neatly summarized each fungus, including its identifying features, distribution on the termite body, life cycle, and impact on individual termites and the colony as a whole.

Thinking back about all the ectoparasitic fungi in the review, a few stand out for Wilson. One of them is the Termitaria fungus that got this whole project rolling. “It’s the only one I’ve seen that has anything like those symmetrical lesions we found. Other fungi, such as Dimeromyces, will have a single column where the spores are produced and they look like little stalks that rise up off the termite here and there, but with Termitaria, the lesion is basically formed of many of these columns of spores, so it is kind of like a compound version of what happens with other fungi,” she says. Another intriguing fungus is Ophiocordyceps, which waits to release its spores and reproduce until a pair of termites begin digging a site for a new nest, she says. “It’s during this point that a giant spore-producing stalk will come out of the ground and release its spores. The spores are then spread and buried to grow almost like a plant. It was interesting that, in this case, the fungus needs the termites to dig out a perfect spot for it to grow.”

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