Effects of temperature on trematode-mediated impacts on a model amphipod host species by Kum C. Shim A thesis submitted to the faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science Department of Biology Carleton University Ottawa, Ontario © 2011, Kum C. 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While these forms may be included Bien que ces formulaires aient inclus dans in the document page count, their la pagination, il n'y aura aucun contenu removal does not represent any loss manquant. of content from the thesis. 1*1 Canada ABSTRACT I conducted laboratory experiments to assess the influence of temperature in the shedding of Gynaecotyla adunca trematode cercariae from its first intermediate host, the snail Ilyanassa obsoleta, and transmission of these cercariae to its second intermediate host, the amphipod Corophium volutator. An increase in temperature resulted in a significant increase in cercariae emergence from snails over 24hr but not over 32 days and reduced the viability of the cercariae. Increase temperature did not impact the snails but was detrimental to the amphipods regardless of infection status. Across 4 mudflats, I investigated the relationship between levels of trematode infection in snails, snail density, and surface temperatures in May and July 2010. Snail density and infection levels increased in the 4 mudflats with higher temperatures in July. The increases in infection levels was not linked to snail density but to temperature increments, indicating a possible climate change scenario. iii ACKNOWLEDGEMENTS First of all, I would like to thank my supervisor Mark Forbes. Without his charisma, great input of ideas and advice, I would still be doing this masters project for the next 2 years! His passion on everything biological was extremely contagious, and it was a pleasure to just listen to him talk about science either in our weekly lab meetings or at the pub. Thank you, Mark, for taking me on; you have made me a better scientist! I would also like to thank the "Maritime group", fellow students and professors at the University of New Brunswick and Mount Allison University: Dr. Myriam Barbeau, Dr. Diana Hamilton, Travis Gerwing, Dr. David Drolet, Justin Murray, Mike Coffin, Trevor Bringloe, Stephanie MaCneil, Alyssa Allen, and Jenna Quinn. They not only offered professional advice and help in my field work, but also gave me a place to stay while away in the field, friendship, and the occasional beer in the cabin by the sea. You guys made my fieldwork easy and fun! I would like to specially thank the Department of Biology at Mount Allison University for allowing me to use their facilities to store and dissect my snails and amphipods. Dr. Diana Hamilton also opened the doors of her lab and offered its contents for me to use in the field, and I am very grateful for that. Many thanks also go to my field assistant for the spring and summer of 2010: Deanna Michelle. Without her, fieldwork would have been almost next to impossible. Thank you for putting up with my shenanigans! I would also like to thank my lab-mates (my lab siblings): Julia Mlynarek, Wayne Knee, Sam Iverson, Greg Bulte, Stacey Robinson, and Andrew Morrill for their constant iv input in my work. They always had advice that seemed small at that time but that turned out to be of great importance in shaping my final work. And they never turned down a beer at Mike's, which made my studies at Carleton U. much more enjoyable! I should thank all my fellow biology grad students and support staff (i.e. Ed Bruggink) here at Carleton U. for their friendship, advices, and help in my work. When I needed some pipette or a test tube rack to conduct experiments in the lab, they always went out of their ways to find the materials I needed. And finally, I would like to thank Montserrat "Montse" Bassa Etxaurren (mi Catalana favorita!) for showing me that there was such a thing as a life outside of the lab. I needed that daily break; otherwise I would have turned into a mad scientist, pale blue with overexposure to fluorescent light and potbellied after so many hours in front of the computer. Gracias Montse! v TABLE OF CONTENTS Page Abstract iii Acknowledgements iv Table of Contents vi List of Tables ix List of Figures x General Introduction 1 Chapter 1. Effects of temperature on a model host parasite system 5 Introduction 5 Materials and methods 7 Collecting and keeping of experimental specimens 7 Experiment 1: Emergence of G. adunca parasites from I. obsoleta mud snails 9 Experiment 2: Parasite survivorship and swimming activity 10 Experiment 3: Infectivity of parasites at 17°C and 22°C 10 Experiment 4: Survivorship of infected amphipods at 3 temperatures 11 Experiment 5: Snail survival and long-term cercariae shedding at different temperatures 12 Statistical analysis 14 Results 14 vi TABLE OF CONTENTS (continued) Page Experiment 1: Emergence of G. adunca parasites from I. obsoleta mud snails 14 Experiment 2: Parasite survivorship and swimming activity 15 Experiment 3: Infectivity of parasites at 17°C and 22°C 16 Experiment 4: Survivorship of infected amphipods at 3 temperatures 17 Experiment 5: Snail survival and long-term cercariae shedding at different temperatures 17 Discussion 19 Chapter 2. The relation of temperature, snail density, and prevalence of infection by trematodes in the Upper Bay of Fundy 37 Introduction 37 Materials and methods 39 Snail sampling 39 Snail densities and mudflat surface temperature data 40 Statistical analysis 40 Results 41 Prevalence of infection in snails 41 Snail densities 41 Mudflat surface temperature 42 vii TABLE OF CONTENTS (continued) Page Relationship between mudflat surface temperature, snail density, and trematode infection levels 42 Discussion 43 Relation of temperature, snail density, and prevalence levels of infection 43 Prevalence levels of infection of Gynaecotyla adunca in the field 44 Effect of trematodes on snail populations 45 Peculiarities of Moose Cove mudflat 46 Conclusion 47 Summary and Conclusions 56 Literature Cited 59 viii LIST OF TABLES Table Page 1.1 Number of cercariae emerging at 17°C after first day on experiment 1 25 1.2 Lab-induced infections of C. volutator 26 2.1 Sampled mudflats locations and dates 48 2.2 Number of snails collected and their infection status 49 2.3 Prevalence levels of infection in snails 50 2.4 Snail density on each mudflat by month 51 2.5 Differences on snail densities between May and July 51 2.6 Average surface temperatures on the 4 mudflats in May and July 52 2.7 t-tests on surface temperature differences between May and July for each mudflat 52 2.8 Mudflat surface temperature, snail density, and trematode infection levels in the 4 mudflats 53 IX LIST OF FIGURES Figure Page 1.1 Graphical representation of laboratory experiments 27 1.2 G. adunca parasite inside C. volutator 28 1.3 Mean number of cercariae emerging from snails 29 1.4 Survival curve of cercariae at 2 temperatures 30 1.5 Swimming activity of cercariae at 2 temperatures 31 1.6 Lab-induced number of infections in C. volutator 32 1.7 Survivorship of infected and uninfected C. volutator at 3 temperatures 33 1.8 Long term cercaria emergence from snails 34 1.9 Average number of cercariae emerged for 33 days at 2 temperatures treatments in experiment 5 35 1.10 Time to flip of infected and uninfected snails at 2 temperatures 36 2.1 Prevalence levels of infection in May and July for 4 mudflats 54 2.2 Prevalence levels of infection vs. snail density in May and July for 4 mudflats 55 x 1 GENERAL INTRODUCTION Climate change has been linked to increased disease in humans and wildlife. For example, the recent global decline on amphibians due to epidemics of chytrid fungus has been blamed on warming brought about by climate change (Pounds et al., 2006), and bleaching and death of corals around the world have also been attributed to severe warming periods (Harvell, et al., 1999).