Millipedes and Mealworms and Mucoromycota. Oh my!

Published by Cori VanGalder on

Millipedes and Mealworms and Mucoromycota. Oh my!

Submitted by: Angie Macias, PhD Student

Brian Lovett, Post-doc

Matt Kasson, Associate Professor

In the Kasson Lab at West Virginia University, we are trying to understand how millipedes and fungi interact. Fungivorous millipedes are a wonderful (and understudied) system for investigating fungal biodiversity, but the closest fungivorous millipedes (Brachycybe spp.) reside in the southern part of the state, a good distance from Morgantown. Years ago, my advisor Matt Kasson, several other members of the lab, and I drove 15 hours in a rented van to sample these millipedes in the Ouachita Mountains of Arkansas and Oklahoma for several unforgettable days. This and other multi-day sampling trips in 2015 and 2017 laid the foundation for my Master’s thesis on, “Diversity and function of fungi associated with the fungivorous millipede, Brachycybe lecontii,” which was published in Fungal Ecology in 2019.

Me, showing sampled millipedes in southern West Virginia
Sampling fungivorous millipedes at Mt. Nebo State Park, Arkansas in April 2016. From left to right: Matt Kasson, me, Kristen Wickert, and Matt Berger

From my Brachycybe lecontii collections in southeastern Oklahoma, I isolated a putative new fungal genus related to Apophysomyces, a fungus known to cause severe mucormycosis in immunocompetent patients. A particularly devastating outbreak caused by A. trapeziformis was reported ~5 years earlier to our discovery: ~190 miles due north from our Oklahoma collection site, in Joplin, Missouri, following an EF-5 tornado in 2011. The discovery of our novel fungal genus and its close ties with opportunistic human pathogenic fungi (Apophysomyces and Saksenaea) prompted further investigation involving phylogenetics, pathogenicity testing on various invertebrate models including both waxworms and Brachycybe millipedes, and genome sequencing.

Initial bioassays suggested that this fungus was not a millipede pathogen, but more recent investigations have uncovered phenotypic differences between strains that justified direct pathogenicity comparisons. Together with Matt and Kasson Lab postdoc Brian Lovett, we decided to test the pathogenicity for all retained strains on both Brachycybe millipedes and mealworm beetle larvae. We initially intended to assess pathogenicity in waxworms as previously used during my thesis work, but pandemics have a way of impacting just about every aspect of our lives. There have been mass shortages of waxworms at pet stores due to supply being unable to meet anxious pet owner demand.

Our bioassays, which involve exposing live arthropods to colonized fungal culture plates, are straightforward under normal conditions. These types of assays are beneficial because they can serve to evaluate nutritional and pathogenic lifestyles of fungal associates simultaneously. But given the ongoing pandemic, Brian, Matt, and I had to improvise to conduct the research while minimizing contact.

A week ago, Matt and Brian, driving separate cars, headed to Chief Logan State Park in Logan County, West Virginia, some 200 miles southwest of Morgantown, to collect adult millipedes for my bioassays. This was Brian’s first trip seeing and sampling these marvelous creatures!

The masked Kasson lab postdoc Brian Lovett displays Brachycybe found at Chief Logan State Park during their pandemic collecting trip.
Brachycybe lecontii munching on fungus and pondering their quasi-subterranean existence

With Brian’s sharp eye and Matt’s sampling experience we quickly amassed ~75 individuals. These millipedes were placed in a large container along with the decaying logs they feed on and transported directly to my house for a masked handoff and at-home “bench” experiments. Even though West Virginia University has recently enacted procedures to allow researchers back into their labs, it made the most sense for me to set up and observe these bioassays from home. This will limit my travel to and from campus to better protect me and the campus community. This pandemic certainly has added wrinkles to our plan, but with a bit of ingenuity, our mycology research could continue. These bioassays are ongoing, and as I trace circles around my apartment in self-isolation, these millipedes will trace circles around their new homes decorated with delicious (or deadly) fungus. Stay tuned!

Mealworms and their chewing marks on a colonized plate
Brachycybe on a colonized plate
Brachycybe on a negative control plate
My makeshift “lab bench” (usually occupied with an unfinished jigsaw puzzle) with the remaining millipedes not used in the experiment resting in the the terrarium, and the fungal culture plates with Brachycybe and mealworms.
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