Do fungi have parasites?

Parasite ecologists spend copious time studying parasitic fungi. For instance, we’re interested in controlling the fungal pathogens responsible for the wildlife diseases that have decimated populations of amphibians, bats, and snakes. And we’re fascinated by the Cordyceps fungi that manipulate the behavior of ants and other insects. But how often do we study parasites that infect fungi (i.e., host = fungus)? Before I tackle this question, here’s a little backstory:

Last week, I went grocery shopping and bought some baby portabella mushrooms. I was feeling lazy, so I bought them pre-sliced and packaged in a cardboard box, which had an open top and was clearly labelled “sliced baby portabella mushrooms”. When I was checking out, the adult human bagging my groceries picked up the box and asked, “Are these vegetables?”

Yes, a piece of my soul died. But the educator inside me immediately announced, without distress or pause, “Oh, no, they aren’t. We generally eat three types of organisms: (1) Animals, where meat comes from, (2) plants, where vegetables come from, and (3) fungi, where mushrooms come from.” And while the woman nodded, seeming to confirm this information from some previous memory, a different, dark voice in my head added, “…and they all have worms.”

Fortunately, some intelligent internal filter kept me from saying the last bit out loud. But as I made my way to my car, I became increasingly concerned that even though I could tell you what kinds of parasites infect most plant and animal host taxa, and I knew that fungi must have parasites, I didn’t know which parasites infected fungi.

I did some googling as soon as I arrived home, and I learned that fungi have fungal, bacterial, and nematode parasites. Larval flies in mushroom gills can also be considered parasites of fungi. But overall, I didn’t find much information about parasites of fungi in my (admittedly not exhaustive) search. It might be that (1) I gave up too soon, (2) we don’t use classical parasitological terms for parasites of fungi, and/or (3) we study parasites of fungi less than those of animals and plants.

If you’re an expert on the parasites of fungi, please share your wisdom with us!

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Moa extinctions caused even moa parasite co-extinctions

Happy Valentine’s Day, Everyone! I only ever blog about papers that I love, and today is no exception. But in honor of this holiday, I’m going to break from tradition and blog about a paper that I love and I co-wrote, and I hope that you’ll forgive my shameless plug.

Within the parasite conservation literature, there exists a paradox: we expect that many, many parasite species should be threatened by co-extinction with their threatened host species, yet we have documented few parasite co-extinctions. If parasite species are so vulnerable, why haven’t we seen more co-extinction events? It might be that parasites are not as vulnerable to co-extinction as we originally assumed. (I could write several blog posts about that possibility, and perhaps one day I will.) Another possibility is that many co-extinctions have occurred, but we failed to notice and/or document them. The latter possibility is the topic of today’s post.

In order to document an extinction (or co-extinction), we need to know two things. First, we need to know that the species once existed. To document which species once lived, we usually rely on historical resources: fossilized remains, museum specimens, published scientific studies or surveys, and even old books/diaries/letters. But many species don’t fossilize well, and many more are too small, cryptic, or seemingly important to end up in museum collections, scientific studies, or other historical records. Second, we need to know that the species doesn’t exist anymore. Documenting the absence of a species is incredibly difficult; its only really possible via exhaustive surveying. That’s why we are sometimes pleasantly surprised when a thought-to-be-extinct species is suddenly found living somewhere unexpected, still hanging in there.

For parasites, I like to think of these two documentation steps as compiling/comparing passenger lists. To know that a parasite species once existed on a host species, we need to create a historical passenger list for that host species. It is hardest to (re)create a complete passenger list for a host species that went extinct (=sank) long ago. But it’s also very difficult to document the parasite passenger lists for host species that are currently threatened (=sinking), because they might have already lost some passengers (e.g., if we de-loused the hosts when we brought them into cavity), or the hosts might be too rare or difficult to thoroughly sample for parasites. Once we have recreated the best historical passenger list that we can – which are probably incomplete, but better than nothing – we need to compare it to all of the parasite passenger lists for all extant host species, to see if any extant host species served as “life boats” that carried some parasite species into the present. As I mentioned last week, we are far from having sampled all extant parasite species on all extant host species, so we’re currently working with incomplete present-day parasite passenger list.

Given all of the difficulties described above, it’s not surprising that we have documented so few parasite co-extinctions! But this week in PNAS, Boast et al. (2018) published a great paper that convincingly documents the co-extinction of a few parasite species that once infected the now-extinct moa (giant flightless birds from ancient New Zealand). They used ancient DNA to reconstruct the best ever ancient passenger list for several moa species, and they were able to show that some parasite species survived to present day on other bird species (e.g., the kiwi), while others did not. You should definitely give their paper a read!

But if you want a shorter, bloggier version of the parasite story, you could also go read the open access commentary about Boast et al.’s paper that I co-wrote. It was super fun to write, because we were allowed to talk about parasite co-extinction and fossil poop at the same time, and it was especially fun because I was invited to co-author the piece by my science hero. (Thanks, Kevin!)

I think those are enough warm, fuzzy, parasite valentine feels for now. Happy reading!

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Which (parasite) species should we study?

Over the past 2-3 years, I have become increasingly (and perhaps obsessively) interested in parasite extinctions and parasite conservation. I’ve blogged about parasite conservation a few times (here and here), but I’ve half-written about three times as many posts that I never published. Apparently, it’s quite difficult to distill topics near and dear to you into 500 word essays! But in celebration and preparation for an upcoming ESA organized oral session (yessssssss, we were accepted!), I’m going to power through and write a series of blog posts that try to encapsulate perspectives and theory regarding parasite conservation. I’m going to start easy today, though. Instead of asking which parasite species we should conserve (if any), I’m going to think about which parasite species scientists should study.

These thoughts require some backstory. Two weeks ago, I found out that all of John Lawton’s View from the Park essays from Oikos have been compiled into this list. I read a bunch of them, of course, and one of them really resonated with me. His essay, “On the behaviour of autecologists and the crisis of extinction”, is about birds and all other  species, but it could easily be interpreted as an essay about the study of parasites. Here’s the first quote that made me think about parasites:

“One of the most repeated facts wheeled out in current discussions about biodiversity, be it in learned articles, newspaper reports or political debate, is that taxonomists have described approximately 1.7 million species, whilst the best current estimate for the total number of species on earth is 12.5 million. This is clearly a serious problem, and one that demands urgent attention (e.g. P. H. Raven and E. 0. Wilson (1992) Science 258, 1099).”

This idea – that we have named/described a tiny fraction of all existing species – is also popular in the parasite literature. People are still revising and debating estimates of the total number of parasite species in the world (e.g., here), but no matter what the current best-estimate is, we still haven’t described most of them. Therefore, everyone seems to agree that we have a (parasite) taxonomy crisis, that we desperately need more people naming/describing more (parasite) species, and that Taxonomist Appreciation Day should happen more than once per year.

But here’s a quote that hit me harder:

“Intriguingly, I have never seen anybody discuss what we actually know about the 1.7 million [species] that do have names. Overwhelmingly the answer will be nothing, except where they were collected, and what they look like…To use an analogy, not only do we have a hopelessly incomplete white pages telephone directory for the planet’s inhabitants, we have an even worse set of yellow pages.”

Ouch. As the author of the Parasite Ecology Blog, I’d love to tell you that we know tons about parasite ecology. Collectively, we do. But we know nothing about the ecology of most named/described parasite species. Why is that? Here are three reasons, which are neither mutually exclusive nor a complete list:

Potential reason 1: Parasites often have complex life cycles, where different ontogenetic stages occur in different host species (or the environment). For instance, when we find a new adult trematode in a bird host, name it, and describe it – which, coincidentally, requires much time/work – we’re still missing all the details about the rest of that parasite’s life cycle. Does it have one other host species? Two? 25? Which species? Etc.

This problem is relevant for some free-living species, too (e.g., which caterpillar turns into this butterfly?). But it’s a particularly common and difficult problem in the study of parasites.

Potential reason 2: Parasites often live inside their hosts, making it difficult for us to observe them in action, or to know if/when hosts became infected.

Potential reason 3: We lack the interest/incentive to dig into the ecology of most parasite species. I’ll come back to this in a second.

The Lawton essay goes on to ponder which species we should study in detail. He notes that we currently focus on specific taxa (e.g., vertebrates) in specific geographic regions (e.g., temperate areas), and argues that we should develop a stratified sampling method, instead – some kind of “major, coordinated effort by whole organism biologists to attempt a systematic sampling of the autecology and behaviour of the earth’s biota.”

Parasite ecologists also focus on specific taxa in specific regions. We’re highly motivated to study parasites that infect people and our domesticated species, especially in temperate regions. We also give much attention to parasites that have strong impacts on populations of important game species and some wildlife species. That isn’t to say that we don’t know anything about the ecology of parasite species from other host species. For instance, we know a lot about some of the cool parasites that manipulate their hosts’ behavior. But are we missing important basic ecological principles by focusing heavily on parasites in particularly important host species or particularly “cool” parasites?

You won’t be shocked to learn that I don’t have immediate answers to these questions. Lawton’s proposal to systematically sample more species for detailed ecological studies sounds awesome, but it also sounds highly difficult to organize and implement, even if we only consider parasites. But this is definitely something worth thinking about! Because as Lawton said:

“The problem has close parallels with the agonising debate over which species to conserve, assuming we have any choice at all in the matter.”

For parasites, there will be little to no support for conserving the parasite species that we know the most about: those that harm humans. (In fact, we’re actively trying to eradicate some of the most heavily studied parasites, like the Guinea worm.) How does one work towards conserving taxa whose best-known species are detrimental for people?

Very carefully?

January Parasite Haiku

To reach my 2018 #260papers goal, I jumped on board with a useful accountability system: tweeting my progress.  Tara Stewart was doing the same thing, and she found a brilliant way to motivate me to read more – we’re summarizing the papers that we read with haiku!! I thought y’all might like to see some of the parasite-themed haiku. If you want to join us, feel free to tweet me yours, and I’ll share them next month!

 

Vicarious Parasitology

I’ve lost count of how many times some awesome parasite ecologist has told me that Armand Kuris’s parasitology course changed their science/life. Since I find myself living in SB this quarter, I’m taking this amazing opportunity to sit in on Armand’s class at UCSB. If you haven’t had the same opportunity and you want to live vicariously through me, you can follow along on Twitter (@parasiteecology), where I’ll be posting the best nuggets.

New Parasite Ecology Papers – January 2018

If you set a New Year’s resolution to read #260papers this year, you might want to check out some of these recent gems. (I’m not providing all of the citation info, in an attempt to prevent accidental inflation of Google Scholar citation indices. So you’ll need to click through for full info.) And if you’re interested in what I’m reading in 2018, you can check my #260papers Twitter thread.

Rabies elimination research: juxtaposing optimism, pragmatism and realism

Corals hosting symbiotic hydrozoans are less susceptible to predation and disease

Disease implications of animal social network structure: a synthesis across social systems

Wildlife disease ecology from the individual to the population: Insights from a long-term study of a naturally infected European badger population

Parasites at Risk – Insights from an Endangered Marsupial

To Reduce the Global Burden of Human Schistosomiasis, Use ‘Old Fashioned’ Snail Control

Contact networks structured by sex underpin sex-specific epidemiology of infection

Best parasite ecology cartoon of 2017?

Happy New Year!

Before we leave 2017 behind us, let’s take a walk down memory lane, and re-visit some of the blog’s best parasite ecology cartoons. At the end, you can vote on your favorite 2017 cartoon.

If you want to delve even further into the past, you can also check out some of the previous best-of-the-best winners: In 2013, the winner was “Social Networking in Lemurs,” a cartoon about this study that painted lice on lemurs to infer lemur contacts. In 2014, the winner was “Oldest Trick in the Book,” a romantic cartoon about a snail who was castrated by trematodes. In 2015, the winner was “Bring out yer dead (prairie dogs),” a Monty Python reference tied to a cool prairie dog plague paper. And in 2016, the winner was my cartoon rendering of Frogald Trump.

Here are the cartoons that I’ll open the voting for this year:

(1) Ticks suck moose dry

mooseandticks

(2) Parasite valentine

iencyst

(3) Orange amphipod zombie apocalypse

amphipods2

(4) Parasites and de-extinction

mammoth

(5) This terrifying clown isopod

Scarasite

Here’s the poll! You can only vote for one cartoon.