THERMAL TOLERANCES OF AN ENDEMIC HOT SPRING SNAIL PHYSELLA WRIGHTI TE AND CLARKE (MOLLUSCA: PHYSIDAE) A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements For the Degree of Master of Science in Biology University of Regina By Erika Kirsten Helmond Regina, Saskatchewan July 2020 Copyright 2020: Erika Helmond UNIVERSITY OF REGINA FACULTY OF GRADUATE STUDIES AND RESEARCH SUPERVISORY AND EXAMINING COMMITTEE Erika Kirsten Helmond, candidate for the degree of Master of Science in Biology, has presented a thesis titled, Thermal Tolerances of an Endemic Hot Spring Snail Physella wrighti Te and Clarke (Mollusca: Physidae), in an oral examination held on July 28, 2020. The following committee members have found the thesis acceptable in form and content, and that the candidate demonstrated satisfactory knowledge of the subject material. External Examiner: *Prof. Bruce Leighton, Simon Fraser University Co-Supervisor: *Dr. Kerri FInlay, Department of Biology Co-Supervisor: *Dr. Cory Sheffield, Adjunct Committee Member: *Dr. Mel Hart, Department of BIology Committee Member: *Jennifer Heron, Adjunct Chair of Defense: *Dr. Maria Velez, Department of Geology *All present via Zoom ABSTRACT Physella wrighti (Te and Clarke, 1985) is an Endangered freshwater snail endemic to the Liard Hot Springs in northern British Columbia. It inhabits water temperatures from 23.5oC to 36oC and is active year-round. Despite its conservation status, little else is known about this species. To advance our understanding of P. wrighti in its environment, I investigated how water temperature affects aspects of its life history in a lab setting. I first investigated if P. wrighti would be more active in the scotophase versus the photophase at 30oC and observed no differences in activity level. I tested if P. wrighti had a preferred water temperature by allowing snails to explore a gradient of temperatures, and determined that the snails preferred 23oC. I reared snails in 13oC (cold), 23oC (warm), and 33oC (hot) water to examine if water temperature would affect the snail’s period of greatest activity, behaviour, survivability, number of egg masses produced, number of eggs per mass, egg volume, egg mass viability, and incubation period. I found no differences in activity level and no difference in behaviour except snails in hot water left the water more often and crawled farther away. Snails in the hot water experienced complete mortality with an average survival of 7 days; snails in warm and cold water survived an average of 84 and 240 days, respectively. Snails in warm water produced the most egg masses, with an average 348 masses compared to 39 and 5 masses in cold and warm water, respectively. The number of eggs per mass was greatest in the cold water, with an average 11 eggs compared to 5 and 6 eggs in warm and hot water, respectively. I found no difference in egg volume between water temperatures, but mass viability was highest in warm water. The incubation period was shortest in hot water and longest in cold water. These data suggest P. wrighti grows and survives better i in water temperatures at the low end of the range observed in its current habitat and may only be tolerating the warmer water. This has implications for the ecology and conservation of this species. ii ACKNOWLEDGEMENTS I want to acknowledge my supervisors Dr. Kerri Finlay and Dr. Cory Sheffield, and my committee members Dr. Mel Hart and Jennifer Heron, for whom their patience, guidance, and support, through this project have been invaluable to me and helped me greatly in my professional development. I thank Dr. Mark Vanderwel for his willingness and unending patience and support in helping me to develop an understanding of statistics. I want to thank Xingzi Zhou and Ann King for their help during my project. Xingzi’s work in helping me monitor aquarium conditions and providing me with additional aquarium observations and Ann’s aid with data entry are greatly appreciated. I thank Dawn Marks and Corey McCowan for their help during fieldwork. I want to note that Dawn’s ability to keep field notes is inspirational and provided me with excellent examples of how to improve my field note skills. I also thank the Greater Vancouver Zoo and Andrea Gieliens, Lead Biologist, for providing me with some perspective on aquarium operations. Furthermore, I want to thank the Leavitt Lab for their help during my preliminary work, as this aided me in determining where to focus my time and resources. Likewise, I want to thank my fellow students. There is a great community of students at the University of Regina. I thoroughly enjoyed spending time with them and always appreciated our brainstorming sessions. Finally, I would like to thank my funding partners: the University of Regina, the British Columbia Ministry of Environment and Climate Change Strategy, the Royal Saskatchewan Museum, the Friends of the Royal Saskatchewan Museum, and Fisheries and Ocean Canada. Without their support, none of this would have been possible. iii DEDICATION I dedicate this thesis to my family: Dan Helmond, Wendy Helmond, Myckala Helmond, and Trevor Helmond. I cannot thank you enough for your constant support throughout all the challenges and fun times that come with working on a project like this. All of your interest in this tiny little snail has made working on this project even more fun than I could have imagined. I always enjoy spending time discussing my project with you and cannot say enough how much I appreciate that you never got bored listening to my many stories and reflections. iv TABLE OF CONTENTS ABSTRACT ........................................................................................................................ i ACKNOWLEDGEMENTS ............................................................................................ iii DEDICATION.................................................................................................................. iv TABLE OF CONTENTS ................................................................................................. v LIST OF FIGURES .......................................................................................................... x CHAPTER 1: INTRODUCTION TO PHYSELLA WRIGHTI AND THE LIARD HOT SPRINGS, AND RESEARCH OBJECTIVES ..................................................... 1 1.1 History of the Liard Hot Springs ....................................................................... 5 1.2 Physical description of Physella wrighti ............................................................. 9 1.3 Life history of Physella wrighti ......................................................................... 13 1.4 Conservation status of Physella wrighti ........................................................... 14 1.5 Population Threats of Physella wrighti ............................................................ 15 1.6 Research objectives ............................................................................................ 17 CHAPTER 2: EFFECTS OF WATER TEMPERATURE ON THE ACTIVITY, BEHAVIOUR, AND SURVIVORSHIP OF PHYSELLA WRIGHTI ......................... 19 2.1 Introduction........................................................................................................ 19 v 2.2 Experimental Methods ...................................................................................... 23 2.2.1 Field Collection of Physella wrighti .......................................................... 23 2.2.2 Feeding Physella wrighti ............................................................................ 25 2.2.3 Observed Period of Greatest Activity – Constant Temperature ........... 25 2.2.4 Determining the Temperature Preference for Physella wrighti ............. 26 2.2.5 Observed Period of Greatest Activity – Varying Temperatures ........... 30 2.2.6 Behavioural Observations of Physella wrighti ......................................... 31 2.2.7 Determining Survivorship of Mature Physella wrighti ........................... 31 2.3 Results ................................................................................................................. 33 2.3.1 Observed Period of Greatest Activity – Constant Temperature ........... 33 2.3.2 Determining the Temperature Preference for Physella wrighti ............. 33 2.3.3 Observed Period of Greatest Activity – Varying Temperatures ........... 35 2.3.4 Behavioural Observations of Physella wrighti ......................................... 35 2.3.5 Determining Survivorship of Mature Physella wrighti ........................... 37 2.4 Discussion ........................................................................................................... 42 vi CHAPTER 3: THE EFFECTS OF TEMPERATURE ON ASPECTS OF REPRODUCTION OF PHYSELLA WRIGHTI ........................................................... 51 3.1 Introduction........................................................................................................ 51 3.2 Experimental Methods ...................................................................................... 52 3.2.1 The Number of Egg Masses Produced by Physella wrighti .................... 53 3.2.2 The Number of Eggs per Mass Produced by Physella wrighti ............... 53 3.2.3 Determining Differences in the Size of Eggs Laid by Physella wrighti.. 54 3.2.4 Viability of Eggs per Egg Mass Produced by Physella wrighti .............. 56 3.2.5 Physella wrighti Embryo Incubation Period ...........................................