Date of Award
Undergraduate Honors Thesis
Bachelor of Arts in Biology
Dr. Paul Bradley
Globally there is a biodiversity crisis, with many groups of species threatened with extinction due to changes in the environment and human impacts. Amphibians are one such group and according to the IUCN, over 30% of amphibians are threatened by extinction. There are many factors have that can explain the decline of amphibians including pollution, habitat loss, climate change and disease. One factor is chytridiomycosis, an emerging infectious disease caused by the chytrid Batrachochytrium dendrobatidis. The chytrid enters the keratinized skin of the amphibian and asexually reproduces, where it disrupts host functions, often leading to host death.
Due to the severity of the disease, mitigation strategies are needed. Current strategies such as fungicides and “frog hotels” are not sufficient due to adverse effects and limitations. However, microorganisms recently have indicated potential for being used as a mitigation strategy. Some species of microorganisms have been observed to reduce the amount of viable B. dendrobatidis in freshwater environments and species can reduce infection strength. One promising group of microorganisms that can remove B. dendrobatidis are Daphnia spp., planktonic crustaceans that live in freshwater and filter feed on unicellular organisms. We hypothesize that B. dendrobatidis is a viable food source for Daphnia magna and additionally will not be toxic to the D. magna.
In a laboratory experiment under controlled conditions, one set of D. magna was exposed to B. dendrobatidis as the only food source for seven days. Another set of D. magna was exposed to dechlorinated water as a control. Under a fluorescent microscope B. dendrobatidis was observed in the gut of D. magna that had been fed the B. dendrobatidis and had survived the course of seven days. The survival rates between the two experimental treatments did not differ, however B. dendrobatidis was observed to not be toxic to D. magna. Although these results did not determine if B. dendrobatidis is a viable food source for D. magna, it does suggest D. magna as a potential mitigation strategy. Further experiments need to be conducted to determine to which extent Daphnia can be used as a mitigation strategy.
Digital USD Citation
Thomas, Taylor, "Daphnia: A Possible Way to Combat a Deadly Amphibian Pathogen" (2017). Undergraduate Honors Theses. 47.