New AmNat paper on effects of invasive species on disease


Daphnia lumholtzi (upper left) and Daphnia dentifera (lower right). Photo by Bella Oleksy

We have a paper in the November issue of the American Naturalist! The lead author on the paper is former lab postdoc Catherine Searle, who is now an Assistant Professor at Purdue University. The paper is entitled, “Population Density, Not Host Competence, Drives Patterns of Disease in an Invaded Community“. The paper was the subject of a press release by UMich, entitled “Invasive Species May Unexpectedly Reduce Disease Prevalence“. The paper focuses on the potential impacts of the invasive species Daphnia lumholtzi on a native host (Daphnia dentifera) and a common native parasite (Metschnikowia bicuspidata).

In addition to Cat and Meg, the authors on the paper are Mike Cortez (our theory collaborator at Utah State) and other members of Meghan Duffy’s lab at the University of Michigan, including technicians Katherine Hunsberger and Isabella Oleksy (now a graduate student at Colorado State), graduate students Dylan Grippi (now at the US FDA) and Clara Shaw, and undergraduates Solanus de la Serna, Chloe Lash, and Kailash Dhir.

Welcome to new lab undergrads!


We had four new undergrads join the lab this fall! Morgan Rondinelli is working with Mary on a project related to Pasteuria and UV. McKenna Turrill, Rachel DeCaluwe, and Stephanie Roskowski are all working with Nina on different projects related to Spirobacillus. We’re excited to have them join the lab! We’re also happy that Rebecca Bilich and Naomi Huntley have stayed on the lab. More info on our lab undergrads can be found on the People page.

Meg tweetstorms pretty plankton photos


I spent a while taking photos of plankton yesterday, and decided to tweet some of them. I figured I’d aggregate the photos and info here, too. The tweets start here and should hopefully all thread; they’re numbered, with only one numbering error I think (there are two 26’s). But I thought compiling the photos and info here, too, might be more stable as a long term way of pointing people to the info. If you’re interested in seeing the responses to the tweets, click the link ahead. But these two may have been my favorites:

I started out with this photo of a Chaoborus (phantom midge) larva. If you were a Daphnia, you really wouldn’t want to see this:chaob-bf-2-sr

Chaoborus are the major invertebrate predator on Daphnia in our lakes. They are gape-limited predators, so prefer smaller prey.

This is a Ceriodaphnia:


She is even smaller than a Daphnia, so she’s even more vulnerable to predation by Chaoborus.

Ceriodaphnia “dilute” disease for Daphnia: they consume spores, so reduce disease in our focal host, Daphnia dentifera.

This is Daphnia dentifera, the species I’ve worked on the most. Isn’t she pretty? This photo might be my new favorite:


Or is this one my new favorite? So many choices! Either way, this is a very pretty, very happy Daphnia:


I said that Ceriodaphnia “dilute” (that is, reduce) disease in Daphnia dentifera. They do that by eating spores.

Ceriodaphnia consumes spores, but usually doesn’t get infected. In doing so, spores lose infectivity, protecting Daphnia from infection.

Let’s return to Chaoborus, which were up near the top of this tweetstorm/post. Here’s another pretty photo, this one in darkfield:


(Darkfield microscopy is when the direct transmitted light is blocked, and only scattered light is used.)

I mentioned that Chaoborus are fierce predators on Daphnia. An interesting thing is that they are “sloppy predators”. When they prey on infected hosts, they release spores back into the water column. This increases disease in Daphnia. We have a new paper by Alex Strauss et al. that looks at how these different food web paths influence disease.

Part of why I was taking photos today was to get photos of Chaoborus and Ceriodaphnia to go along with that story. Here’s one:


And here’s one of Chaoborus, Daphnia dentifera, and Ceriodaphnia. I would not want to be that Ceriodaphnia!


I also took photos today related to a project my grad student Kristel Sanchez is doing. She’s interested in how food influences disease. Kristel is interested in whether food quality and toxin production influence disease outcomes. She’s getting interesting results!

Here are two animals from different treatments. The one on the upper left is uninfected. The one on the lower right has a bacterial parasite:


That was a brightfield image. Here’s a darkfield one of the same pair:


The uninfected one has embryos in her brood chamber. The infected one is white bc she’s filled with spores. She’s also sterile. 😦

Daphnia are transparent because it reduces fish predation. Something I’ve worked on is how being infected increases predation. Being infected increases fish predation a lot. (The fish don’t get infected.) This has really big impacts on epidemics.

Three tweets in a row without a pretty photo. Let’s fix that. Here’s a Daphnia dentifera, taken with DIC/Nomarski optics:


Nomarski photos don’t need to have the blue background, but I like it and so try to get it there sometimes.

Nomarski photos of Ceriodaphnia are tough. They are so round their body acts as a prism, as happened here:


All the photos in this thread/post were taken by me, using live animals. They can wiggle around when live, which is tough, but if I preserve them they lose their color. Some people use carbonated water to knock them out without changing color. But I’ve found bubbles cause more problems.

Okay, time for me to get back to work. I hope you enjoyed some pretty plankton photos!

I’d love feedback on whether you found this engaging (people on twitter seemed to like it!) and what other things about Daphnia and/or disease you’d like to know more about!






Welcome to Katie McLean!


Welcome to new PhD student Katie McLean! Katie joins the lab from Westminster College in Utah. She received both a Rackham Merit Fellowship and a National Science Foundation Graduate Research Fellowship (hearing about both on the same day!) Katie is interested in multihost-multipathogen interactions and coinfections. We’re excited to have her in the lab!