Web reduction behaviour and the chemical communication system of the western black widow, Latrodectus hesperus by Catherine Scott B.Sc., Queen’s University, 2008 Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in the Department of Biological Sciences Faculty of Science Catherine Scott 2014 SIMON FRASER UNIVERSITY Fall 2014 Approval Name: Catherine Scott Degree: Master of Science (Biological Sciences) Title: Web reduction behaviour and the chemical communication system of the western black widow, Latrodectus hesperus Examining Committee: Chair: Zamir Punja Position Gerhard Gries Senior Supervisor Professor Maydianne Andrade Supervisor Professor Department of Biological Sciences University of Toronto Scarborough Bernard Roitberg Supervisor Professor Robert Bennett External Examiner Research Associate Royal British Columbia Museum Date Defended/Approved: December 3, 2014 ii Partial Copyright Licence iii Ethics Statement The author, whose name appears on the title page of this work, has obtained, for the research described in this work, either: a. human research ethics approval from the Simon Fraser University Office of Research Ethics, or b. advance approval of the animal care protocol from the University Animal Care Committee of Simon Fraser University; or has conducted the research: c. as a co-investigator, collaborator or research assistant in a research project approved in advance, or d. as a member of a course approved in advance for minimal risk human research, by the Office of Research Ethics. A copy of the approval letter has been filed at the Theses Office of the University Library at the time of submission of this thesis or project. The original application for approval and letter of approval are filed with the relevant offices. Inquiries may be directed to those authorities. Simon Fraser University Library Burnaby, British Columbia, Canada update Spring 2010 iv Abstract In spiders, pheromones mediate intersexual attraction, courtship behaviour, and mate recognition. I studied the chemical communication system of the western black widow spider, Latrodectus hesperus. Females attract males to their webs with silk-borne sex pheromones. Contact with the silk elicits courtship behaviour by males. Often, the courting male engages in web reduction behaviour, during which he excises and bundles up sections of the web and wraps them with his own silk. Using analytical chemistry, and behavioural tests in both the laboratory and the field, I investigated (1) the molecular structure and function of the female’s contact sex pheromone, and (2) the function of web reduction behaviour. A silk-borne contact pheromone elicits web reduction behaviour, and a serine derivative similar to the pheromone of congeneric L. hasselti is one constituent of the multi-component pheromone. Web reduction decreases web attractiveness to rival males in the field, thereby limiting male-male competition. Keywords: animal communication; behaviour; pheromones; spiders; silk iv Dedication For Sam, who introduced me to spiders. v Acknowledgements I gratefully acknowledge the Tsawout First Nation for granting permission to do field work on their beautiful land, and the Capital Regional District for granting permits for spider collection at Island View Beach. I thank my supervisor Gerhard Gries for his endless enthusiasm and support, for always being available to talk through issues big and small, and for believing in me especially when I did not. I thank my committee members Maydianne Andrade and Bernie Roitberg for their excellent guidance and helpful suggestions that have improved this work and my writing immensely. I thank Robb Bennett for agreeing to examine my thesis, and for being an inspirational spider advocate. I thank all of my labmates for advice, support, and friendship during my degree. Special thanks go to Bekka Brodie, Antonia Musso, Eloise Rowland, Chelsea Eby, and Mike Hrabar. I also thank my pseudolabmates Gwylim Blackburn, Tanya Stemberger, and Mike Boers for much needed moral support during the writing of my thesis. I am very grateful to all the undergraduates that volunteered their time and energy to help with maintenance of spiders and laboratory and/or field work: Susan Chen, Chloe Gerak, Devin Kirk, Maïa Smith, and Elaine Wu. I especially thank Samantha Vibert for her mentorship and friendship over the past four years. None of this work would have been possible without her support and insightful guidance. I thank Sean McCann for being my best friend and collaborator, and for assistance with uncountable aspects of this work, including but not limited to photography, videography, field work, experimental design, and manuscript editing. vi Table of Contents Approval .......................................................................................................................... ii Partial Copyright Licence................................................................................................ iii Abstract .......................................................................................................................... iv Dedication ....................................................................................................................... v Acknowledgements ........................................................................................................ vi Table of Contents .......................................................................................................... vii List of Tables .................................................................................................................. ix List of Figures ................................................................................................................. xi Chapter 1. The role of male silk in spider courtship and sexual communication ........................................................................................ 1 1.1. Abstract .................................................................................................................. 1 1.2. Introduction ............................................................................................................. 2 1.2.1. Sexual communication in spiders ............................................................... 2 1.2.2. Spider silk and sexual communication ....................................................... 2 1.2.3. A brief introduction to spider silk ................................................................ 3 1.3. Female silk and sexual communication .................................................................. 3 1.3.1. Female silk: substrate for pheromones ...................................................... 4 1.3.2. Female silk: substrate for transmission of vibratory signals ........................ 5 1.4. Male silk and sexual communication ....................................................................... 5 1.4.1. Male silk: substrate for sex pheromones .................................................... 5 1.4.2. Male silk: cues for assessing competitive conditions .................................. 6 1.5. Male silk use during courtship ................................................................................. 6 1.5.1. Male silk: web modification and silk addition .............................................. 7 Web reduction behaviour ......................................................................................... 7 Web modification: mating threads and webs ........................................................... 9 Silk deposition without web modification................................................................ 10 Web modification and silk addition: inferences and future study ........................... 11 1.5.2. Male silk: the ‘bridal veil’ or mate-binding behaviour ................................ 11 Bridal veils: summary ............................................................................................. 14 1.5.3. Silk-wrapped nuptial gifts ......................................................................... 14 Silk use during mating in a ray spider: A nuptial gift with web modification and possible bridal veil .................................................................................... 16 Nuptial gifts: summary ............................................................................................ 17 1.6. Conclusion ............................................................................................................ 18 Acknowledgements ....................................................................................................... 19 Literature Cited .............................................................................................................. 20 Chapter 2. N-3-Methylbutyryl-O-methylpropanoyl-L-serine methyl ester – pheromone component of western black widow females .................. 45 2.1. Abstract ................................................................................................................ 45 2.2. Introduction ........................................................................................................... 46 2.3. Methods and Materials ......................................................................................... 48 2.3.1. Experimental Animals .............................................................................. 48 2.3.2. Collection of Silk for Behavioural Bioassays ............................................. 48 2.3.3.