Folks, hang on to your butts! There is a new study that just hit the press and it's absolutely nuts. It has so many implications that my head is spinning. Let me tell you about it...
Let's start with a little background on the OE parasite. As anyone who has been around monarchs knows, OE (Ophryocystis elektroscirrha) is a naturally-occurring protozoan parasite that can infect monarchs. It forms long-lasting spores that hang out on the abdomen of adults (pictured above), and they fall off and scatter onto milkweed leaves. The larvae consume the spores when eating the plants, and then the parasite replicates in them, repeating the cycle. In heavy infections, the monarch may not survive to the adult stage, but in many cases the monarch emerges looking completely normal. The only way to tell if they are infected is to look at scotch-tape samples from their abdomen, to see the amber-colored spores, as shown above. For more information on OE, readers can check out the monarchparasites webpage.
Now, you also need to know that for the longest time, we (monarch scientists) have always thought that OE only affected monarchs and their close relatives in the family Danaidae, such as queens and soldiers. In fact, did you know that the first-ever description of OE was in queen butterflies, not monarchs? Anyway, it was always thought that this parasite specialized exclusively on Danaid butterflies. We've always thought this because all efforts to find spores on other butterflies have failed. Years ago Dr. Sonia Altizer had gone through a "lot" of pinned museum specimens of other random butterfly species, to see if she could find any evidence of OE. She couldn't. Keep this in mind, as I'll come back to this.
Now check this out - a new paper was just released by the publishing journal (Journal of Invertebrate Pathology), that throws a giant wrench into this story. The paper was just published online, so this news is as hot-off-the-press as you can get. The paper was written by Ke Gao, Daphne Muijderman, Sarah Nichols, David G. Heckel, Peng Wang, Myron P. Zalucki, and Astrid T. Groot. It sounds like some of these researchers are from the "Institute for Biodiversity and Ecosystem Dynamics", at the University of Amsterdam. Here is a link to the paper. I'm not sure if this journal has free access though.
This paper describes the discovery of a "new" type of OE parasite, complete with football-shaped spores and everything, and that affects certain species of moths, of all things! The paper reports that the new confirmed host species are three noctuid moths, Helicoverpa armigera (cotton bollworm moth), H. assulta (oriental tobacco budworm) and H. punctigera (Australian bollworm moth), plus one true butterfly, Parthenos sylvia, also called "the clipper". These species inhabit Europe, China and even Africa, and they each feed on a variety of plants - none of them feeds on milkweed!
Here are a couple of pictures of one of the host species described in the paper, the "cotton bollworm moth". These are simply copied from the Wikipedia entry on this species. Apparently, this is a very, very common crop pest in Europe and Africa, and there are some in Australia.
I look at these new hosts and think this is crazy. These moths and the one butterfly are so far removed from monarchs it's not funny. None of these species ever, ever comes in contact with milkweed, so there is no way this could have been some kind of cross-species spillover. In other words, there is no way that these moths could have accidentally consumed OE spores on milkweeds. And, these species all reside in places (and habitats) where they would never even come into contact with monarchs or their relatives.
The authors reported that they made this discovery in their lab, when they were rearing these species for research purposes. They said that they noticed some specimens not developing properly into the adult stage, which resembled the symptoms of OE infections in monarchs. So they tested some with the scotch tape method and bingo, they saw OE spores under the microscope!
They followed up the discovery with some measurements of the spores, and it turns out they are slightly smaller than the monarch-OE spores. Also, they did some genetic comparisons and found that this new parasite is 95% similar to monarch-OE. And get this, they then gave these spores to monarch larvae in their lab, and nearly all of the monarchs became infected! But, when they gave monarch-OE spores to these other Lepidopterans, only about half of them became infected. This sort of makes sense, since the two parasites appear to be related, but slightly different.
They also followed up their lab discovery with some field collections of these moths and butterflies. They report collecting 20-60 specimens each from Australia, China and Spain. Nearly all collections contained some infected individuals (prevalence was 0%, 2%, 7%, 10% and 19% in their collections). So this clearly is not an incidental lab contamination. This is a real, honest-to-goodness naturally-occurring parasite in the wild!
Here another cool thing about this new parasite - based on the genetic analyses they performed and reported on, it looks like the monarch OE could have been derived from this "new" OE parasite! That's right, it looks like the monarch-OE is a "genetic offshoot" of this other OE! What the hell? So it might be that monarchs and other Danaids may have originally gotten their version of the parasite (thousands of years ago) from this other OE. Another way to think about it, is that this "new" OE could very well be the ancestral version! My mind has officially been blown.
Here is another interesting bit - years ago, when Sonia Altizer was in the midst of her PhD studies, she had been sent some Helicoverpa moths by a colleague, who suspected they had OE. She recalls looking at them under the microscope and seeing what looked like OE. She was so busy at the time that she didn't have time to follow up on this, and she just chocked it up to an accidental lab contamination, or something like that, and she moved on and forgot about it. But, once this new paper came out, she went digging through her archived specimens and she actually found these moths from years ago! Here is a picture.
Sure enough, these look just like OE spores in monarchs. They have the same football shape, amber/brown color, and I did some quick measurements, and they seem to be similar in size to monarch-OE spores (11 microns long). The paper reports their spores being a little smaller. I'm not sure why.
OK, are you ready to hear the really, really, REALLY crazy part of this story? The authors report that they conducted their own brief survey of OE prevalence in other Lepidopterans by examining specimens that were shipped to a butterfly house in Amsterdam. It was the butterfly garden at Artis Zoo, in Amsterdam, Netherlands. I'm not sure why they chose to do it this way, perhaps they figured this would be a good way to sample a lot of species all in one place, and it was close to their university in Amsterdam. I did a quick google search for this place. Below is a random image from the internet from this place...
It looks to me to be a pretty typical butterfly house, with a greenhouse-style setting, lots of plants and trees, and butterflies flying around. The authors reported that they surveyed 32 species of butterflies and moths that were shipped here during one summer in 2018. It sounds like these were coming from all over the place - they state these originated from Asia, Africa and South America!
Here is what they stated they found from these samples - From the specimens collected in the Amsterdam Zoo, two out of 32 butterfly species were found to carry OE or OE-like parasites. Specifically, 86% of D. plexippus (12 out of 14 individuals) that were originally from South America were infected and 58% of Parthenos sylvia (Nymphalidae) (15 out of 26 individuals) originating from Asia were infected.
That's right, monarchs were shipped to Amsterdam, from South America, and they were nearly all infected with OE. The authors did not seem to know if they had the monarch-OE, or this new OE. In fact, I'm not sure you'd be able to tell just by looking under a microscope. To me, those moth-OE spores I photographed look just like monarch-OE spores. The other infections were in the clipper butterflies, which look like this:
This butterfly originates in Asia. It was being shipped to Amsterdam. And they were infected.
OK, blown away by all of this? I am too. I'm not sure where to start, the bit about the "new" OE species (which may not be as new as we thought) is crazy. The fact that these new hosts have nothing to do with Danaids is crazy - this means there could be other butterflies or moths out there that also have their own versions of OE, and we don't even know about it. The bit about these butterflies being shipped (globally) while carrying this parasite is also nuts! Who regulates these shipments? Anyone?
Here's my final two cents - just for perspective, keep in mind that all indications are that these parasites are naturally-occurring in the wild, meaning these are not something that we need to get rid of in nature. But, in a time when there are global losses of insects, the last thing we should be doing (as a society) is moving parasites between continents.
Share this post with everyone you know who is involved with monarchs. Right now. The monarch world needs to know about this new paper.
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