Member Spotlight: Dr. Alyssa-Lois Gehman

By Stephanie Rizzo


For this Member Spotlight, I interviewed Dr. Alyssa-Lois Gehman, a Postdoctoral Research Fellow at the University of British Columbia and the Hakai Institute (working with Dr. Chris Harley). Dr. Gehman’s most recent research involves symbiotic endolithic microbe alteration of host morphology and vulnerability to increasing temperatures.


Q: When did you become interested in studying parasites?


Dr. Gehman in the field. Photography courtesy of Keith Holmes.

A: In undergraduate at Colorado College, I was lucky enough to sign up to take Parasitic Protozoa with Ron Hathaway. He was a phenomenal story teller, and I was quickly fascinated by parasites. It took me a while to realize I could combine my love of parasites with my love of marine invertebrate research, but once I did, I was hooked. I have kept in touch with Ron, once sending him a shipment of rhizocephalan infected shrimp that we had collected so that he and his students could use them in the scanning electron microscopy course he taught.


Q: What advice would you give to students that are interested in the study of parasites?


A: If you are in undergraduate, I recommend looking around to see if your university has any parasitology courses. The courses could be in a range of departments, from biology to veterinary and public health departments. I think taking courses in as wide a spread of different disciplines would be super helpful for deciding which type of parasitology interests you (wildlife, domestic animals, humans, public health?). It will also give you a broad base to think on throughout your career, because the underlying host-parasite relationship is somewhat similar no matter what the host you are considering, and seeing the similarities and differences between how the different disciplines consider the same topic could lead to amazing new insights.


If you are looking into graduate programs, I recommend finding an advisor who has worked with parasites in the past. It is not a requirement, but it will be easier to do your research and to get a broad understanding of the field. I did my PhD in the Odum School of Ecology, which I highly recommend.


Q: Your current research is primarily focused on rocky intertidal systems along the Pacific coast. What changes due to climate change have you seen or do you anticipate being of concern in relation to parasite communities and/or abundance?


A: This is a great question – I am really interested in how parasites will respond to climate change. From my work in Georgia, we found that parasitized crabs had altered thermal responses from their uninfected counterparts. In this case, we found that the infected crabs were more vulnerable to high temperature, and modeling predicts that the parasite would not survive a 2ºC temperature increase.

Peltogaster sp. Infecting Pagurus hirsutiusculus. Photo by Dr. Gehman from her current research project in British Columbia.

We are beginning to have information on how parasites respond to temperature, but I think we are a long way from knowing generally how infection alters parasitized host thermal performance. The evidence we have so far is that some parasites can increase host thermal tolerance, some reduce it, and some have no effect. My hope is that if we can increase the number of host-parasite pairs that have known thermal performance responses (never mind co-infected hosts), we could find some generalizations around what sort of response we might expect.


Q: You have done some work with the Rhizocephalan barnacle parasite (Loxothylacus panopasi), which you lovingly refer to as the “Neuterator”. What, in your opinion, is the most interesting thing about this parasite?


A: Wow, I forgot that I had called them that, good work finding that quote. I think Rhizocephalans are absolutely fascinating. I think one draw for me is that their lifecycle seems so unlikely, and yet there are many of them. Rhizocephalan larvae have separate sexes, so not only does the female have to find and infect a susceptible host, but the male then has to find a host that has already been infected by a female parasite. Generally, the unknown is what drives my curiosity, and I think there remains so much to find out about Rhizocephalan ecology.

Eurypanopeus depressus infected by Loxothylacus panopaei and Dr. Gehman. Taken during her PhD dissertation research project conducted in the marshes of Georgia. Photography courtesy of Andy Tucker.

Q: What are your thoughts on utilizing parasites as bioindicators (ecosystem health, toxins, pollutants, etc.) in marine systems? Why do you feel marine parasite ecology research is important?


A: We are in an era of persistent change, and I think that how climate change will alter the balance of host-parasite interactions is one of the biggest unknowns. Parasites are important parts of their communities and ecosystems, and we are just beginning to understand how they fit in to that bigger picture.


I think our need to know more about marine parasites can come from multiple angles; as climate change alters host abundance and distribution, it may also be altering their parasites distributions, and we might lose parasites we never even knew about in the process. Conversely, changes in the environment could favor a parasite in a way that could lead to high levels of mortality of their host, leading to an unexpected loss of the host species.


Q: In your research with endolithic parasites and California mussels, you suggest that the parasite may be helping the mussel endure higher temperatures than they are normally used to. How often do you think parasites are having these beneficial, but so far mostly overlooked effects?


A: I think this is a super interesting question that we need to know more about. The definition of a ‘parasite’ has likely influenced our ability to think about this kind of question, since by definition a parasite should have a negative effect on their host. I was lucky enough to share a lab with Eugene Kozloff when I was in graduate school and when I think about this question my conversations with him come to mind. He was insistent that we should consider all parasites (and mutualists) symbionts, with a range of possible positive, neutral or negative effects. There are examples of classical parasites that appear to have positive effects, and one way that can happen is through parasite-parasite interactions within a host. I think as we start studying co-infection the experiments are going to reveal interesting interactions. I’m not sure how widespread I think the combination of positive and negative effects are, but I do think that it will be a fruitful direction for research for a while yet.


Q: What do you do in your free time?


A: Community is important to me, so I make sure to spend time with family and friends. As for hobbies, I am a bit of a hobby collector, so the answer to this question could be long. I love to be physically active, which can take the form of skiing, hiking, mountain biking, acroyoga and/or various other circus arts. Because of the current pandemic I am spending much more time at home, so I have been voraciously reading, knitting, learning to play ukulele and have taken up an ‘at home’ yoga practice.


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