Soldier trematodes

Many animal species have fascinatingly complex social systems, but the pinnacle of sociality is relatively rare: the reproductive division of labor. Taxa that have separate castes of reproductive and non-reproductive individuals include the hymenopteran insects (ants, bees, and wasps), gall-forming aphids, termites, ambrosia beetles, sponge-dwelling shrimp, naked mole rats, and – because this is a Parasite Ecology blog – trematode parasites.

You’ve probably seen photos of the insane phenotypic differences between castes in some species; for instance, the difference between a queen fire ant and a worker fire ant (amazing photo by Alex Wild):


Or between queen, worker, and soldier termites (photo from here):


Trematode rediae have equally obvious caste differences, where reproductive rediae are huge and full of developing offspring, whereas soldier rediae are tiny with relatively large pharynxes (photo from here). And they don’t just look different; these castes are also spatially segregated, and they have unique behaviors. Reproductive individuals tend to hang out in the host snail’s gonads, while soldier trematodes tend to hang out in the mantle. And reproductive rediae rarely attack rediae from other trematode species, whereas soldier rediae readily attack invading species.


But despite these differences between reproductive and soldier rediae, the reproductive division of labor in first intermediate host trematode colonies wasn’t discovered until a few years ago. And until January (Garcia-Vedrenne et al. 2017), soldier rediae had only been documented in one trematode superfamily: the Echinostomatoidea.

It would not have been surprising if echinostomoids were the only trematodes to have soldier rediae, because echinostomoids are known for their ability to “fight” other trematode species. For instance, in a well-studied salt marsh system, echinostomoids sit at the top of a trematode dominance hierarchy, where they can successfully invade and conquer a California horn snail infected by a different trematode species, and they can successfully fight off invasions of their snail by other trematode species. But we now know that at least four species of heterophyid trematodes, which fall in the middle of that dominance hierarchy, also have a distinct soldier caste (Garcia-Vedrenne et al. 2017)!


This is a pretty big addition to our existing knowledge of these systems, and it makes one wonder how many other trematode species have undocumented soldier castes. Check out the paper to learn more!


Garcia-Vedrenne, A.E., A.C.E. Quintana, A.M. DeRogatis, C.M. Dover, M. Lopez, A. Kuris, and R.F. Hechinger. 2017. Trematodes with a reproductive division of labour: heterophyids also have a soldier caste and early infections reveal how colonies become structured. International Journal for Parasitology, 47(1): 41-50.

Parasite Valentines

I usually blog about STIs on Valentine’s Day. But this year, I’ve decided to spread the parasite love in a different way – with a few awesome links and a valentine. If you want to help spread the parasite love, you are more than welcome to send me parasite valentines via Twitter. I’ll be waiting.

Why killer viruses are on the rise

An awesome new symbiont was recently discovered. It’s a beetle that pretends to be an ant’s butt.

Superspreaders played a big role  in the Ebola epidemiciencyst

What’s on my reading list

The flu and job search committee duties have contributed to me falling behind in reading and blogging. In an attempt to get back on track, I’m posting this week’s reading list (in no particular order).

  1. Pepin, et al. (2017). Inferring infection hazard in wildlife populations by linking data across individual and population scales. Ecology Letters.
  2.  Cizauskas et al. (2017). Parasite vulnerability to climate change: an evidence-based functional trait approach. Royal Society Open Science.
  3. Betini et al. (2017). Why are we not evaluating multiple competing hypotheses in ecology and evolution? Royal Society Open Science.
  4. Weinersmith et al. (2017). Tales from the crypt: a parasitoid manipulates the behaviour of its parasite host. Proceedings of the Royal Society B.
  5. Cohen et al. (2017) The thermal mismatch hypothesis explains host susceptibility to an emerging infectious disease. Ecology Letters.
  6. Garcia-Vedrenne et al. (2017). Trematodes with a reproductive division of labour: heterophyids also have a soldier caste and early infections reveal how colonies become structured. International Journal for Parasitology.

What am I forgetting?

Compiling List of Jobs in Parasitology and Parasite Ecology

Hello Readers!

Jobs in parasitology and/or parasite ecology have been recurring topics on the blog in the past few months. For instance, are there government jobs for people studying wildlife parasites? And are you more likely to find a job as a “parasitologist” or as a “disease ecologist?” I’ve also received several recent emails from students looking for parasite-related research opportunities, and I wasn’t as helpful as I wish I could have been. So, I’m happy announce that I’m going to start compiling a list of parasite-related jobs for all career stages on this blog. If you know of a relevant job that should be added to the list, you can post it in the comments or send it via email to dinoverm (@)

Please share widely!

Zebra-eating plants spread anthrax

Carnivorous plants have always fascinated me. So when I saw this link on Facebook a few years ago, I was quite excited! The link (and this video) claim that the bromeliad Puya chilensis eats sheep. That’s right. A plant that eats sheep! The sheep are ensnared in the plant’s thorns until they succumb to exhaustion and die, and then their rotting carcasses feed the plant. We don’t actually know that the plants have evolved to “catch” and eat mammals, of course. An alternative explanation is that sheep are just rather unintelligent. But the idea is fascinating.

Whether some plants intentionally kill mammals or not is up for debate, but plants do eat mammals. Kind of. For instance, in Namibia, zebra carcasses increase soil nutrient concentrations for at least a year after the animal dies (Turner et al. 2014), and during that initial year, grass biomass near carcasses is higher than randomly-selected carcass-free sites (Turner et al. 2014).

The higher grass biomass near carcasses causes zebra and other ungulates to be attracted to carcass sites to forage (Turner et al. 2014). You might be thinking that foraging near a dead zebra body might be a bad idea for a zebra, and you’d be right. Namibia is one location where anthrax (caused by the bacterial pathogen Bacillus anthracis) naturally infects wildlife, so contacting a carcass could mean contacting anthrax spores. And zebras should worry about more than just the carcasses; the soil, grass roots, and grass at carcass sites all harbor anthrax spores, at least for the first year after the carcass appears (Turner et al. 2014).

If visiting carcass sites exposes zebras to a potentially lethal pathogen, why don’t zebras avoid carcasses? Well, they do, but only a little bit. When a carcass is relatively fresh, zebras are less likely to visit carcass sites than control sites, but that avoidance doesn’t last until all of the anthrax has left the grass. Therefore, sexy, delicious grass may facilitate anthrax infections in zebra.


Turner WC et al. 2014 Fatal attraction: vegetation responses to nutrient inputs attract herbivores to infectious anthrax carcass sites. Proc. R. Soc. B 281: 20141785.

Parasites in the News – January 2017

If you haven’t voted on the best 2016 Parasite Ecology cartoon yet, please do! If you did, thanks! Have some links!

Not Up for Debate: The Science Behind Vaccination (New York Times)

We are resurfacing this article in light of the news that Robert Kennedy Jr., an anti-vaccine crusader, has said he has been asked by President-elect Trump to lead an immunization safety committee.

Relatedly, it looks like the measles vaccine protects children from more than measles.

A research crew went on a quest for the ‘Lost City of the Monkey God.’ They nearly lost their faces for it.”

And finally, the prawns-eat-snails-to-reduce-Schistosoma-transmission project in Senegal was covered by BBC news, reminding me of that one time I tried to draw a motorcycle.


Yikes. That prawn terminator, though.

Have a good weekend!

Best parasite ecology cartoon of 2016?

It’s the first week of the new year, which means that you get to vote on the best parasite ecology cartoon from last year! 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. And in 2015, the winner was “Bring out yer dead (prairie dogs),” a Monty Python reference tied to a cool prairie dog plague paper. So which 2016 cartoon was best? I’m opening up the voting for these candidates:

(1) The case of the not-so-boring isopods


(2) A sworm of soldier trematodes


(3) Slugs. Ruin. Everything.


(4) The Curse of the Magical Seed Dispenser


(5) Frogald Stump bans immigration and destroys frog metapopulation stability


(6) “Parasite” fashion show


(7) House cats out of the dog house after Toxoplasma accusations 


(8) Overly-frequent arousal can kill you


(9) Weird vibrations


(10) Survival of the fattest


(11) May the force of infection be with you


Let the voting begin! You can pick your top three favorites using this poll: