Mystery Growths on Termites Lead to Major Review of Ectoparasitic Fungi

By 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

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.”

Antennopsis is one of the fungi described in the new Annals of the Entomological Society review paper, which summarizes information gleaned from nearly 100 scientific papers dating as far back as 1914, and offering an up-to-date summary of 34 termite-infesting fungal species. This illustration of Antennopsis‘ life cycle shows how it reproduces asexually and generates spores, called conidia, that land on and stick to the termite’s outer surface, or cuticle. (Image originally published in Wilson et al, 2021, Annals of the Entomological Society of America)

Dimeromyces reproduces sexually. Its ascospores (spores contained in a sac-like structure called an ascus) land on the termite’s cuticle and sprout a vegetative structure known as a thallus. Subsequently, female and male structures are formed and involved in the development of more ascospores, which are then released to start the cycle again. (Image originally published in Wilson et al, 2021, Annals of the Entomological Society of America)

More in Store

Now that the review is complete, Wilson is putting the finishing touches on a description of the Termitaria fungus they found, and then she plans to continue studying fungus-termite associations. She is especially interested in termite and fungal ecology to shed light on how and why they co-evolved, and she believes many of the answers may lie in already collected specimens waiting to be examined in museums. “The AMNH has the largest contemporary termite collection in the world, and it’s really well curated, so it would be really cool to look through the termite specimens in the museum, extensively check them, and document other fungal species that could be found on them,” she says, noting that she also plans to reach out to other termite-fungal researchers to learn about their findings and add to the overall knowledge base.

On an even broader level, Wilson says she would eventually like to apply for funding to begin digitizing the AMNH collection of termites and possibly even the wood-digesting protists in the termite gut. “That would be really interesting and just be so useful for pushing the field forward.”

Leslie Mertz, Ph.D., writes about science and runs an educational insect-identification website, www.knowyourinsects.org. She resides in northern Michigan.