Senior Project Advisor

Dietmar Schwarz

Document Type


Publication Date

Spring 2020


Drosophila melanogaster, Entomophthora muscae, behavior, immunity, fitness, behavior manipulation, thermal preference


Animals use various strategies to defend against pathogens. Behavioral fever, or fighting infection by moving to warm locations, is seen in many ectotherms. The behavior-manipulating fungal pathogen Entomophthora muscae infects numerous dipterans, including fruit flies and house flies, Musca domestica. House flies have been shown to exhibit robust behavioral fever early after exposure to E. muscae, then switch to prefer cool temperatures in the later stages of infection. Interestingly, no evidence of behavioral fever in response to any investigated pathogen has been found in the fruit fly, Drosophila melanogaster. However, they have been found to prefer cool temperatures during infections. To determine if fruit flies utilize behavioral fever, cold-seeking, or both during E. muscae infection, we used a two-choice behavioral assay to measure individual temperature preferences of E. muscae-exposed and unexposed flies at early (24-72 hour) and late (72-120 hour) infection time points. In contrast with our expectation from house flies, fruit flies did not exhibit behavioral fever. However, we found significant cold temperature-seeking in flies that died from infection on the day of the assay. To investigate whether this cold-seeking behavior was being caused by the fly or the fungus, we tested the effects of temperature on the fitness of the host, D. melanogaster, and the pathogen, E. muscae, during infection. We found that flies held at low and high temperatures for 24 hours before death from infection laid no eggs at the lower temperature. This could suggest that the fly is not causing the cold-seeking behavior because there is no apparent fitness benefit at low temperatures. Conversely, cadavers sporulating at the low temperature tended to cause more flies to eventually die from infection, indicating that E. muscae infects flies more effectively at lower temperatures. Preliminarily, our results support fungal control of temperature preference before death, though further testing is needed. The idea that E. muscae benefits from colder temperatures, and therefore drives cold-seeking behavior in D. melanogaster at the end of the host’s life, expands our current knowledge about host behavior manipulation by E. muscae and provides a fascinating avenue for investigating the mechanisms by which this fungus manipulates complex behaviors in its animal host.

Subjects - Topical (LCSH)

Drosophila melanogaster--Pathogens; Drosophila melanogaster--Behavior; Drosophila melanogaster--Effect of temperature on


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