Erica Berent

The Infection Dynamics of a Fungal Pathogen in Stream-Dwelling Northern Two-Lined Salamanders in Wooster, Ohio

April 2, 2021   /  

Student Name: Erica Berent
Major(s): Biology
Minor(s): Chemistry
Advisor(s): Dr. Richard Lehtinen

How familiar are you with salamanders? You probably know that they live in streams and under rocks, but did you know that many are affected by a disease that is causing the decline of amphibian populations worldwide? This disease is called chytridiomycosis and it is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). The goal of my research was to assess this pathogen in stream-dwelling northern two-lined salamanders in Wooster Memorial Park. I wanted to see the proportion of individuals that were infected by this pathogen as well as how intense the infection was. I also looked at a potentially beneficial bacterium, Janthinobacterium lividum (J. lividum), that may help fight off Bd infection. In order to test this, I captured salamanders and obtained skin swabs. These swabs contained the DNA of micro-organisms, which would include both Bd and J. lividum. I extracted this DNA and examined it to see if either of these micro-organisms were present. I also looked at data from past years, to get a better idea for how infection dynamics have changed over time. The results I gathered showed that there was no difference between infection prevalence between years, nor between sampled creeks and seasons. I did see a significant increase in infection intensity since 2016, but no difference was seen between creeks and seasons. I was unable to determine the relationship between J. lividum and Bd, but I was able to confirm that J. lividum could be naturally found on the skin of northern two-lined salamanders.


 
Erica will be online to field comments on April 16: 4-6 pm EDT (PST 1pm-3pm, Africa/Europe: late evening)

64 thoughts on “The Infection Dynamics of a Fungal Pathogen in Stream-Dwelling Northern Two-Lined Salamanders in Wooster, Ohio”

  1. Congratulations on your findings and for adding to a study that I’m certain future Wooster Scots will continue. Great Job

  2. Such a cool project, Erica! If you could go back and offer advice to yourself when starting this project, what would it be?

    1. Thank you! If I had to give myself advice it would be to not stress when things don’t go the way I intended. Everything will work itself out even if the outcome is unexpected.

  3. Really interesting and impressive. It’s really concerning that amphibian populations are under so many stresses from human effects on the environment. Congratulations on your IS and graduation!

    1. Thank you for your interest! This pathogen is definitely a concern in certain species. I hope my research will aid in finding a solution.

  4. Congrats on all your hard work, Erica! Do you think that curative treatment for BD in wild salamander populations would be feasible/useful in combating the pathogen’s impact on species? Also, how should humans alter their behavior to protect the two-lined salamander from BD?

    1. Thanks Tess! Very good question! I know some research has been done on introducing microbes like J. lividum into the soil to help protect against Bd infection, so it is feasible that a similar method could be using in treating the disease. In general, I think humans could help by being conscientious about the introduction of invasive species. At this point it will be impossible yo completely eradicate Bd, but steps can be taken to minimize its spread and prevent similar pathogens from emerging.

  5. Awesome presentation!
    What other animals host Bd? Do they also have the possibility of having J. lividum on their skin?

    1. Thank you Nicole! I know that Bd can be found in many amphibian species besides this one, as well as on crayfish and the feet of geese. Although I am unsure whether J. lividum can also be found on these organisms.

  6. Such cool work, Erica! I can see the thought and intentionality you put into your project. Congratulations on such a huge accomplishment, sending love <3

    1. Thank you so much Ellie! That really means a lot to hear you say that. I hope you have been doing well. Monkeys did not feel the same without you!

  7. Congratulations on completing your IS! I really enjoyed your study. Do you think that you will continue to find information on your study in grad school/ on your next journey?

    1. Hi Chamari! Thank you! I definitely enjoyed working with this species, so I would love to continue working with them or a similar species in the future.

  8. Hi Erica! Great job on your presentation and continuing such a long and important study. Has J. lividum been found on any other organism?

    1. Thanks Julia! I did not focus on J. lividum as much as I had intended, so I am not completely sure what other organisms it can be found in. It can exist for long periods of time the soil so it is definitely possible that it could be found in organisms other than amphibians.

  9. Hi Erica – Amazing Job! Hopefully in the future someone will be able to continue your study on J. lividum so the impact on fungal load can be investigated. Do you have any thoughts on what could have been the cause of the PCR issues?

    1. Thank you Lydia! I hope my research will contribute to future work done on this topic. A for the PCR assay, I have a few ideas. It is possible that there was an issue with the mastermix. Another possibility was that the thermocycler conditions were not completely optimized. There also could have been an issue with the primers I used. PCR is a finicky technique, and it sometimes takes a lot of time to get it optimized completely. Had I had more time, I like to think that I would have been able to figure out the issue and get it working consistently.

  10. Well done, Erica. I don’t know where you will be going to grad school, but if you ever need help wading through swamp or river to catch more critters, count me in. (Nic’s mother)
    Congratulations!

    1. Thank you so much! I would like to attend grad school eventually, so I’ll keep you in mind when when planning for sample collection haha.

  11. This is fantastic, Erica! Thank you for the easy-to-follow explanations of your work. There is definitely potential for further research and I really like the connection you were able to make to Wooster! Congratulations!

    1. Thanks Maggie! The question you asked is essentially the question my IS sought to answer. In general the infectiousness of Bd is naturally increasing over time. This has been observed in amphibian populations worldwide. It is likely that Bd infectiousness will continue to increase as it continues to evolve and as environmental conditions change.

  12. Congratulations Erica! Very interesting study. Also, very helpful for Wooster to keep this study g0ing and adding to the long standing data set. Great job!

  13. Congratulations! This research was incredibly fascinating, and your presentation was fantastic. Out of curiosity, you’d mentioned that this was a particularly large data collection for the study of Bd – are there other sample pools that are currently being used in this examination for salamanders specifically, or just for species susceptible to Bd in general?

    1. Thanks Lily! I am glad you found this interesting! The data used in this research was a subset of a dataset that includes all salamander species in Wooster Memorial Park that have been collected over the past five years. I simply filtered the data to look only at stream-dwelling northern two-lined salamanders. In fact, my sample collection was not limited to northern two-lines. I swabbed any salamander I found to contribute to the larger dataset.

  14. Excellent talk and research project! What would you suggest people do if they want to help conserve amphibian populations?

    1. Thank you Dr. Ison! My best advice would be for people to educate themselves on the population declines that are happening around the world. It is unlikely that Bd will ever be completely eradicated, but if more people are aware of the disease, then they can be more careful about minimizing its spread.

  15. Great job Erica, and congratulations! I had fun catching (or in my case failing to catch) salamanders with you.

    1. Thanks Stephanie! I also enjoyed out salamander catching outings (regardless of how sidetracked we got).

  16. Awesome work Erica!

    But enough of the congratulations, let’s get down to the nuts and bolts. I have a few questions about your methodology and data.

    How many observations (i.e., Salamanders) were included in the data you analyzed, and…

    …how were potential observations selected for inclusion?

    1. Thanks Uncle Matt! In my analysis, I had 282 salamander skin swabs over all years, creeks, and seasons. Out of these, 42 were Bd positive. The inclusion criteria were pretty straightforward. I included all stream-dwelling northern two-lined salamander swabs present in the dataset. This included both adults and juveniles.

  17. Wonderful presentation! You mentioned that Bd seemed to be increasing over time. In your view, is there cause for concern that a critical mass could be reached where the effects on the salamanders or the surrounding ecosystem could be more pronounced?

    1. Thank you! Based on what I have learned, there is not much of concern that a critical mass will have a significant affect. I believe this because the fungal load observed in this research is already relatively high, and no negative affects have been observed. However, that may not be the case in other amphibian species which experience severe symptoms and mortality from this disease.

  18. Hi Erica. Nicely done and certainly sets the stage for any future work. Too bad you could not get the PCR to work better. We have had many spotted salamanders in our yard and it will be interesting to see if there numbers increase or decrease in in the coming years.

    1. Thank you very much! I did not know that spotted salamanders were abundant where you lived. I will have to try and find some next time I visit.

  19. You reported no significant differences in bd prevalence across years, creeks and seasons. What type of analyses did you conduct to test for significant differences?

    1. The statistical test I conducted was a generalized linear mixed model. I used this test because it accounted for the fact that my data was binary (the salamander either had bd or it did not), and it did not require the for the data to be normal.

  20. Hooray for salamander work continuing at Wooster!! I’m so curious about the J. lividum connections- the work never ends! Congrats on an awesome IS! πŸ™‚

    1. Thank you so much! Your research and data was a huge help to me in completing my research.

  21. Awesome job, Erica. I know how hard you worked on this and I’m glad to see it turn out so well.

    I only have one note… include more salamanders in your presentation next time. πŸ™‚

  22. Love the presentation and the salamanders look so cute. One very important question what was your go-to salamander catching process.

    1. Thanks Michael! I also thought the salamanders were cute! The catching process looked like this. We would turn over rocks in streams until we found a salamander. They were then hand-captured (usually because those guys are fast and slippery) and placed in clean plastic bags. We then swabbed them using a cotton swab for 30 seconds in the bag. After swabbing we released them back under the rock where they were found. Nitrile gloves were worn throughout this entire process and switched between salamanders to avoid cross-contamination and inadvertent spread of infection.

  23. Hi Erica! As you know, I’m not a science person, but I was really impressed by your presentation. Not only did you have good general presentation qualities (you didn’t talk too quickly, you had good diction, and your slides were organized well), but you talked about your I.S. in a way that I could understand. I enjoyed learning about your research! You mentioned that you were only able to successfully run seven gels during the experiment. Do you think you may have been able to discover more about Bd’s relationship to J. lividum if there hadn’t been the issues with the gels? Are you planning to continue this research in the future?

    1. Thanks Holly! It really means a lot to hear you say that. I definitely think I could have learned more about this relationship if the PCR and gels had worked. If successful, I would have been able to compare the J. lividum positive individuals with the Bd positive individuals and hopefully draw some conclusions. I do not think I will directly continue this research, but I would love to do similar research in the future. It is my hope that a future IS student will continue where I left off.

  24. You salamanders are so cute! Congrats on a great project and I loved your presentation! πŸ™‚

  25. Great job on your project and presentation, Erica! I’m very proud of you! I can’t recall ever seeing a salamander, but will have to start looking for them in Aunt Kathy’s yard. It’s so hard to believe you’re a college senior already. I know you’ll go far with this knowledge and everything else you’ve learned. Love you!

    1. Thank you see much! I feel like it’s been forever since I’ve last seen you! I miss you lots!

  26. Hi Erica,
    Given all the recent buzz with bats and zoonotic transfer in the context of COVID, it was strangely relieving and fascinating to read about infection dynamics between salamanders. I very much enjoyed your methodical approach to studying infectious and beneficial pathogens, and the inference you were able to draw. Thank you for sharing, and congratulations!

    1. Thank you Arvind! This research was definitely a nice break for me from all the craziness surrounding COVID, but it was interesting how many similarities I found between my research and COVID research. It was really eye-opening to see how interconnected the field of science is.

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