DePaul University Via Sapientiae College of Science and Health Theses and Dissertations College of Science and Health Summer 8-21-2016 Parasite-related modification of multiple traits in an isopod host Tracey J. Park DePaul University, [email protected] Follow this and additional works at: https://via.library.depaul.edu/csh_etd Part of the Biology Commons Recommended Citation Park, Tracey J., "Parasite-related modification of multiple traits in an isopod host" (2016). College of Science and Health Theses and Dissertations. 190. https://via.library.depaul.edu/csh_etd/190 This Thesis is brought to you for free and open access by the College of Science and Health at Via Sapientiae. It has been accepted for inclusion in College of Science and Health Theses and Dissertations by an authorized administrator of Via Sapientiae. For more information, please contact [email protected]. Parasite-related modification of multiple traits in an isopod host A Thesis Presented in Partial Fulfillment of the Requirements for the Degree of Master of Science By: Tracey Park July 2016 Department of Biological Sciences College of Science and Health DePaul University Chicago, Illinois 2 ABSTRACT Parasites are organisms that live on or in hosts, which they typically require to complete their life cycles. Acanthocephalus dirus is an acanthocephalan parasite that exhibits an indirect life cycle that requires two hosts, with a Caecidotea intermedius isopod as the intermediate host and fishes as the definitive hosts, in order to complete its life cycle. Infected C. intermedius individuals have been observed to have altered hiding behavior, in which they have an increased amount of time exposed to predators. Also, infected C. intermedius individuals have demonstrated an increase in activity patterns, which could increase their conspicuousness to visual predators. Infected C. intermedius individuals also exhibit pigmentation dystrophy, which makes infected isopods more conspicuous to visual predators than uninfected isopods. Using a combination of field-based and laboratory-based behavioral trials, I examined the associations of A. dirus infection with behavior (hiding and activity) and body color of male and female isopods. I also examined the relationships between parasite characteristics (intensity and volume) and host trait modification. This study is the first to examine the relationships between effects of infection status in individual C. intermedius and multiple host traits, as well as the correlations among modified host traits and behaviors in both the field- and laboratory-based settings. I tested for sex-associated effects on each of the traits using a Mann-Whitney U test. Spearman rank-order correlations were used to analyze the relationships between pairs of traits both in the field and laboratory experiments. To determine the potential impact of parasite characteristics (intensity and volume) on each of the traits, I used Spearman rank-order 3 correlation analysis on trait measures obtained in the field for behavior (hiding behavior and activity) and the laboratory for color (color score and % color). Infected and uninfected isopods (males and females) differed in hiding behavior in the laboratory. Only infected and uninfected males differed in hiding behavior in the field. Infected and uninfected males did not differ in activity in the field and laboratory. Infected females crossed fewer grid lines than uninfected females in the field and laboratory. These changes in female activity appear to be more likely associated with pathological effects of infection than adaptive manipulation. Infected isopods were lighter in color than uninfected isopods. The pigmentation dystrophy observed in this system may have been an adaptive mechanism used by parasites or a pathological side effect of infection. When using color score as the color measure, there was a positive correlation between color and activity that was present in only uninfected females in the field. However, there was not a correlation between these traits in the laboratory. The correlation between color and activity in uninfected females in the field may not be a meaningful correlation because it was expected that the correlation would occur in a different context, the laboratory, in addition to occurring in the field. Future research is needed to determine the potential significance of the correlations among traits identified in nature and disruptions to these correlations. For the results obtained here, it appears that different traits may be modulated by different mechanisms because the correlations among traits were not consistent between different contexts. 4 ACKNOWLEDGEMENTS I am immensely grateful to several people who have helped me during the course of completing my project. I want to first thank my cohort for all of their support in studying for my oral exams, helping with classes, and providing encouragement throughout my time at DePaul. I want to also thank Alaina, Danielle, Dimitar, Erica, Jordan, Sara, and Tim of the Sparkes laboratory for all of their technical, physical, and emotional support with my thesis - I will always treasure all of our wonderful conversations. Thank you especially to Drew Steffen and Emma Schremp for your valuable time spent helping me with data collection both in the field and in the lab. Melissa Horther, I owe you a special thank you for also helping with data collection and becoming one of my good friends at DePaul. My family and friends have supported me throughout my time at DePaul, and I could not have made it this far without their encouragement. I would like to thank DePaul University and the Biology Department for funding my project and education. Thank you for the experiences you have provided me over these past years. I am also thankful for the opportunities to study and work with such wonderful faculty at DePaul. Dr. Windsor Aguirre and Dr. Kenshu Shimada, thank you for your questions as well as suggestions, they have helped me develop my thesis while keeping the ‘big picture’ in mind. Last, but definitely not least, I would like to thank my advisor, Dr. Timothy Sparkes. Thank you for helping me to create a project and write a thesis that I could be proud of, as well as pushing me to become a better writer and scientist. I am also thankful for your refreshing outlook on science, teaching, and life in general- it helped me put my whole project into perspective. 5 TABLE OF CONTENTS TITLE PAGE 1 ABSTRACT 2 ACKNOWLEDGEMENTS 4 TABLE OF CONTENTS 5 TABLES 7 FIGURES 8 THESIS Introduction 9 Methods Study System 22 Parasite Infection and Multi-Trait Modification 23 Consistency and Repeatability 23 Field and Laboratory Experiments Hiding Behavior (Field) 25 Activity (Field) 26 Hiding Behavior and Activity (Laboratory) Body Color 28 Statistical Analysis 30 Results Parasite Infection and Multi-trait Modification Body Size 33 Hiding Behavior 33 Activity 34 Consistency and Repeatability of Behavior 34 6 Body Color 35 Multi-Trait Correlations 36 Parasite Characteristics and Multi-Trait Expression 37 Discussion Modification of Focal Traits: Hiding Behavior, Activity, Body Color 38 Correlations among Focal Traits and Disruptions in the Correlations 43 Candidate Proximate Mechanisms 45 Correlations between Parasite Characteristics (Intensity and Volume) and Modification of Focal Traits 46 Conclusions 47 Limitations of the Approach 48 REFERENCES 50 7 TABLES TABLE PAGE Table 1: Modification of behavioral and physiological traits of isopods infected by cystacanth- stage Acanthocephalus dirus 61 Table 2: Modification of behavioral and physiological traits of isopods infected by cystacanth- stage Acanthocephalus species in various countries 63 Table 3: Traits of the host, infection status of the host, and location of the trials 65 Table 4: Estimates of consistency and repeatability for each behavior measured in the field and the laboratory 67 Table 5: Partial correlation coefficients between traits for infected and uninfected male and female isopods in the field and laboratory 69 Table 6: Spearman correlation coefficients examining the relationships among traits of the host (field measures) and parasite characteristics 71 Table 7: Host sex, host body size, and parasite characteristics 73 8 FIGURES FIGURE PAGE Figure 1: Locality and depiction of study site 75 Figure 2: Experimental arenas used for behavioral trials 77 Figure 3: An example of a round experimental arena used for the analysis of activity 79 Figure 4: World Color Survey stimulus array used for color analysis 81 Figure 5: An example of a captured image of an isopod that was used for body color analysis with ImageJ 83 Figure 6: Body sizes of infected and uninfected male and female isopods 85 Figure 7: Captured images of isopods for body color analysis 87 Figure 8: Correlation coefficients between traits for infected and uninfected male and female isopods in the field 89 Figure 9: Correlation coefficients between traits for infected and uninfected male and female isopods in the field 91 9 INTRODUCTION A parasite is any organism that lives on or in a host in order to complete its development and reproduction (Moore 2002). Parasites are commonly found in multiple taxa and systems worldwide. As a consequence, most organisms will be infected by at least one parasite within their lifetime. However, parasite infection does not necessarily result in the death of a host. In some cases, parasites may modify the behavioral and physiological traits of one host (intermediate host) to increase