Parasites affect ecosystems: the case of the not-so-boring isopods

One day, I’m going to make a list of all of the cool examples of parasites that substantially alter their host’s morphology. Today is not that day. But I do have a really neat example to add to the future list: FASCINATING BORING ISOPODS.

Mangroves are salt-tolerant trees that are important sources of coastal habitat and erosion control. Many species live in, on, and amongst mangrove roots, including a cute little isopod: Sphaeroma terebrans. The mangroves probably don’t think the isopods are all that cute, though, because the isopods bore into mangrove root tips. It has long been hypothesized that this naughty boring behavior might have big effects on root growth, and a recent field experiment confirmed this suspicion. When isopods were excluded from roots using mesh cages, roots grew 2.5-19 times more than they would have without isopod-excluding cages (Davidson et al. 2016). Protected and control roots were also morphologically distinct in metrics other than total length, and you should see Figure 4 in the open access PDF for a nice visual of that.

During the field experiment, 15% of the protected roots became anchored, while 0% of the control roots became anchored. So it looks like isopods really affect the rate of formation of mangrove habitats and the structure of those habitats! That might have far-reaching impacts on the invertebrate and fish communities that rely on the mangroves.

There are many other parasites in many other habitat-forming host species around the world (e.g., corals, Acacia trees, kelp), which makes one wonder how much global habitat distributions and structure are controlled by our Parasite Overlords…or perhaps that’s just me, writing this blog post at 11:50pm.



Davidson, T. M., G. M. Ruiz, and M. E. Torchin. 2016. Boring crustaceans shape the land–sea interface in brackish Caribbean mangroves. Ecosphere 7(8):e01430. 10.1002/ecs2.1430

Everything you thought you knew about keystone sea stars is wrong

…ok, maybe not everything. I’m just getting into the clickbait title fad. But you probably are incorrectly citing Paine (1966), so you’ll be glad you clicked!

Bob Paine, a giant in ecology, recently passed away. He left behind an incredible legacy of ideas and students, and one insanely famous paper: “Food web complexity and species diversity.” If you’re an ecologist, you know that in the experiment described in that paper, Paine removed sea stars from the rocky intertidal and then recorded what happened. In particular, when sea stars were removed, he found that mussels (a favorite delicacy of sea stars) took over more of the primary substrate, crowding out other space-holding species and thus reducing the total number of space-holding species.

According to a recent paper by Lafferty and Suchanek (2016)(PDF link), ecologists usually cite Paine (1966) when they say something like, “predators increase biodiversity by fostering co-existence among competitors.” Most papers never specify which components of biodiversity actually increase when sea stars are present (i.e., primary space-holders). But it turns out that it is important to be specific, because in the rocky intertidal, sea stars actually greatly reduce biodiversity! By eating mussels, sea stars reduce the surface area of an important 3D habitat full of epibionts and parasites and tiny free-living organisms that live among the mussel shells. So, when you cite Paine (1966), you should specify that sea stars increase primary space-holder biodiversity, but reduce total community diversity.

As a side note, my favorite quote from this paper was: “Whelks are like little wolves in slow motion.” Go read it!


Those purple things are mussels. You get the cartoons you pay for on this blog.😛


Lafferty, K.D., and T.H. Suchanek. 2016. Revisiting Paine’s 1966 Sea Star Removal Experiment, the Most-Cited Empirical Article in the American Naturalist. The American Naturalist.

ESA 2016 Parasite Ecology

ESA 2016 was rather small (and hot), but that didn’t stop a lot of excellent parasite ecology talks from happening! I was consistently impressed with the caliber of the talks: very thorough studies, huge datasets, and so much pretty math!

So uh, you might remember how I was supposed to run an unofficial ESA 2016 Parasite Cartoon Contest. Well, I did, but then I left my notes in the hotel, and I can’t remember all of the cartoons without them. Oops! But based on what I do remember, here are my chosen winners:

Honorable Mention:

One morning, I dragged myself out of bed in time to see an 8:00am talk by Alex Strauss. I was not disappointed by his cartoon performance! Consistent with his excellent use of cartoons in 2014 and 2015, he used cartoons to make some very complex hypotheses regarding the dilution effect very clear for the audience. I could even follow his talk before drinking any coffee!


Noam Ross had a few (adorable) cartoons in his talk. But I’m choosing him as the winner not just for his cute bat cartoon, but because all of his slides were so beautiful. You can go look at them here.

Zika, WNS, Anthrax, Bsal, and more

I hope you’re all preparing your parasite ecology cartoons for your ESA talks next week! I know I am – so I didn’t have time to make one for this week’s post. Oops! Here is some pressing parasite ecology news, instead!

Speaking of conferences, I wish I was at this one. The #WDA2016 tweets are making me jealous.

Zika virus is officially being transmitted by US mosquitoes. Also, we now know that Zika virus can definitely be sexually-transmitted. This has led the CDC to recommend that all pregnant women in the US be screened for infection. (WOW!) If you want to know about Zika in your state, here’s an interactive map that you can use.

Increased temperatures in Siberia thawed out frozen corpses, which led to an Anthrax outbreak in reindeer and herders. Yikes.

This isn’t exactly news, but the USFS has a story map about White Nose Syndrome that might be nice to use in the classroom.

I can’t remember if I already shared this, but the outbreak of turtle herpesvirus at the Great Barrier Reef looks brutal.

There’s a recent article on Bsal and monitoring efforts in the US that has really pretty graphics.

Another parasite ecology bonanza

If you only visit Parasite Ecology for the cartoons, you’re going to be disappointed, again. But if you want to catch up with a bunch of recent cool parasite ecology via a link dump, you’re in luck! Here’s some cool stuff that I read recently:

There are a LOT of parasites in the world, and obviously they don’t all share one common ancestor. So how many times has parasitism independently evolved? An insanely large number of times.

When mosquitoes are nutritionally deprived as larvae, their capacity as human malaria vectors is greatly reduced relative to mosquitoes that weren’t nutritionally deprived.

I also have news from the not-necessarily-parasitism side of the mutualism-parasitism continuum. Do you know what a lichen is? If you answered “a symbiotic relationship between a fungus and an alga,” you answered just like all of the lichen experts of the past century. And you’re wrong.

Sidestepping the issue of whether a parasite ecology blog should feature brood parasites, honeyguides are the kind of brutal that you wouldn’t want to meet in a dark alley. If you don’t believe me, check out “a stab in the dark: chick killing by brood parasitic honeyguides.”

Finally, what’s the best way to control transmission of human schistosomiasis? Snail control is very effective.



Winner of the Unofficial ASP 2016 Cartoon Contest

As promised, I was hunting parasite cartoons at ASP 2016. I’m just going to give you guys the Honorable Mention, the Runner Up, and the Supreme Grandmaster (=Winner) of ASP 2016 parasite cartoons that I saw. I know I missed a bunch of good ones, so forgive me! Next time I’ll scrounge up a team of judges.

If you missed out on the parasite ecology cartoon competition at ASP, don’t despair! There will be another unofficial contest this summer at ESA 2016!

Honorable Mention:

Kevin Lafferty didn’t actually use any cartoons in his talk on ecological methods in parasitology, but he did advertise the Parasite Ecology blog and highlighted the diagram that I made for figuring out where you fall on the parasitologist to disease ecologist gradient. Thanks, Kevin!

 Runner Up:

The Runner Up was S.Y. Wang, whose talk was about infection-mediated temperature selection in tadpoles. Great talk with lots of cartoons!


Congratulations to Sara Weinstein – who talked about the origins of parasitism in Animalia – for being the SUPREME GRANDMASTER of ASP 2016 cartoons! Sara didn’t know it, but I’m a Spongebob fan, and she used all of the main Spongebob characters in one her phylogenies to indicate the mollusks, arthropods, echinoderms, etc. Sara was also the Honorable Mention for last year’s unofficial ESA parasite ecology cartoon contest.