A Cross-Country Cicada Fungus Collaboration! - Observation of the Week, 10/19/21

Our Observation of the Week is this Massospora diceroproctae-infected Florida Keys' Scrub Cicada (Diceroprocta biconica), seen in the United States by @oridgen10!

During the Brood X mass periodical cicada emergence in North America this year, many cicada watchers noticed a strange affliction on some of the emergent adults - their rear ends were gone and had been replaced by a crusty looking fungal mass. This was likely Massospora cicadina, a parasitic fungus that parasitizes only periodical cicadas. There’s a lot we don’t know about these fungi, but what we do know is pretty amazing. 

It’s thought that Massospora spores infect cicadas when they’re still underground, in their mature nymph stage. This is known as a Stage I infection. After they metamorphose, the fungus spreads into the adult host’s abdomen, eventually making part of it slough off and basically “replacing” it with a mass of spores. Even more amazing, at least some Massospora species alter the behavior of its host via chemicals. For example, some infected male cicadas begin behaving like females, causing amorous males to attempt mating with them and thus contracting the spores. This results in a Stage II infection, and the now-infected adults spread the spores that will fall onto the ground and eventually infect the nymphs. You can read more about some of these behaviors here. 

Not all cicadas, however, are periodical - many are “annual,” with emergences happening every year and not as staggered as the periodical species. And of course, there are Massospora species which host on annual cicadas.

Which brings us to Owen Ridgen, currently a student at the University of Toronto, who credits his dad (who in turn was inspired by his dad) for his interest in nature. “I began as mainly a birder,” he says, “but as I've grown older I've branched out and begun to appreciate all forms of life. I have a special interest in odonata (dragonflies and damselflies), lepidoptera, fishes, reef life, freshwater mussels, and reptiles and amphibians.”

While vacationing in the Florida Keys in August, Owen went mothing - “essentially just setting up a white sheet and reflecting a UV or mercury-vapour bulb off of it in order to attract moths, which can then be photographed” - and noticed that a good number of cicadas were also being drawn to his sheet. 

I began to notice that a significant proportion of these cicadas seemed to be missing the back half of their abdomens. One of them even had some chalky-looking material attached to this area. So I uploaded an observation of this cicada to iNat.

Cicada researcher @willc-t noticed Owen’s observation and recognized that the cicada had a Massospora infection. So he in turn emailed Matt Kasson (@millipedeeats, below), a professor at the University of West Virginia.

Dr. Kasson and his lab have been studying this genus since 2016, and in 2020 his lab published the first phylogenetic study of these fungi. Their Massospora diceroproctae specimen came from a Diceroprocta semicincta cicada collected in Arizona - thousands of kilometers away from the Florida Keys. He tells me

The original description for the Massospora from D. semicincta, M. diceroproctae, also listed D. biconica [which Owen observed] as a potential host but the author questioned if it was really the same fungus given the wide stretch of real estate between the Keys and Arizona. In 2006 one of my former grad students photographed a Massospora-infected Diceroprocta biconica with the same purple-colored fungal plug we see from D. semicincta. But his observations were a decade before my lab even started studying these fungi.

So, Dr. Kasson reached out to Owen. 

When I reached out I was disappointed he had not collected the specimen (why would he) but was ecstatic when he said he was still in the area and could go back to where he made the observations and secure several more if possible. We exchanged messages via iNat and he was able to collect us several specimens.

[Once the specimens arrived], my post-doc Dr. Brian Lovett and my PhD student Angie Macias, both who work with me on this group of fungi, processed the samples and we made both slides for microscopy and extracted DNA for our molecular work. Since Angie had already built a nicely resolved phylogeny and deposited representative sequences into GenBank it was just a matter of BLASTing our sequence date we generated to see the percent sequence similarity with M. diceroproctae.

A cross-country collaboration via iNat confirmed a new host for this fungus! 

Owen (above) says he’s not currently studying anything but has some ideas for future projects. He has been on iNat since 2017 and tells me

I typically use iNat every day of my life. Pretty much anything I see that I can get a good picture of, I will upload. But it's more than that, it is also a community that I love to participate in. iNaturalist has inspired me to be far more attentive to the natural world, and seek out organisms that I knew little about before. It's helped me gain a much more holistic view of my environment overall.

(Photo of Dr. Kasson by Amy Metheny. Photo of Owen by David Ridgen.)

- @willc-t is also part of this cicada rediscovery from last year!

- Entomologist Samuel Ramsey discusses cicada mating and Massospora in this video.

Posted on October 19, 2021 09:34 PM by tiwane