The Effect of Antibiotics on Parasite Resistance in Monarch Butterflies Restricted; Files & ToC

Abstract

The monarch butterfly (Danaus plexippus) is renowned for its lengthy migration across the Eastern North American coast. Unfortunately, a protozoan parasite, Ophryocystis elektroscirrha (OE), can cause damage to the wings and lifespan of an infected butterfly, affecting its ability to migrate. While one known way to counteract OE is milkweed plants, some species of which have medicinal chemicals called cardenolides, not much research has explored the possibility of an interaction between the gut microbiome of the monarch and OE. Therefore, using a mix of ampicillin, streptomycin, and tetracycline, we set out to see if the presence and composition of the microbiome impacts the ability of OE to infect monarchs, and to what severity. Our research showed that in the absence of antibiotics, monarchs suffered lower infection when reared on high-cardenolide milkweed than on a low-cardenolide milkweed. In the presence of antibiotics, however, this medicinal effect disappeared, suggesting a role of the gut microbiota in mediating plant-conferred parasite resistance. However, while the antibiotics were proven to be effective against bacteria in a lab setting, there was no quantitative difference between the number of bacteria in the control caterpillars and the caterpillars that were fed antibiotics their whole lives. This suggests that antibiotics affected the composition of the microbiome rather than the overall population density. Bacterial 16s rRNA sequencing is on the way to address this possibility. 

Table of Contents

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About this Honors Thesis

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School	Emory College
Department	Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Ecology
Keyword	Parasitism Tri-Trophic Interactions
Committee Chair / Thesis Advisor	Jacobus de Roode, Emory University
Committee Members	Miguel Reyes, Emory University Martine Brownley, Emory University

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