Direct and indirect effects of a trematode parasite on the endemic freshwater fish Galaxias anomalus Harriet Thomas A thesis submitted for the degree of Master of Science Zoology University of Otago Dunedin, New Zealand September 2013 Dedication For my Father From a young age you inspired the scientist within me, I am forever grateful for your unconditional support and belief in me Abstract Abstract Fish have critical periods during early life where mortality is extremely high. There are a multitude of factors which can influence mortality, however, parasitism is often overlooked as a causal factor of mortality during this period. Understanding the extent to which biotic and abiotic factors, such as parasites, can influence fish survival, is paramount for effective management of threatened species. The purpose of this study was to investigate the effects of a trematode parasite, Telogaster opisthorchis (a parasite known to cause malformations in young fish), on the critical larval stage of its second intermediate fish host Galaxias anomalus, a small, endemic, freshwater fish vulnerable to extinction. The influence of T. opisthorchis on the condition, size, and survival of G. anomalus fish was tested by experimentally infecting larval fish of different ages with different doses under standard conditions. Additionally, the likelihood that parasites cause malformations and their influence on the swimming ability of their hosts were also investigated. Swimming tests were carried out using a unidirectional propeller-driven flume where individual fish swimming ability was monitored over a fixed period. Results demonstrate that T. opisthorchis can affect G. anomalus survival directly via reduced condition, and indirectly via malformations and lowered swimming ability. However there was no effect of parasitism on condition or size, nor was there any effect of infection level on the presence of skeletal malformations, the reasons for which are discussed in the text. The effect of parasitism in early life stages of fish influences survival, and in wild populations, may be exacerbated by additional stressors, with consequences at both the population and community level. iii Acknowledgements Acknowledgements Firstly, I am most grateful for the opportunity to work under the supervision of Robert Poulin. Thank you for the opportunities, and graciously putting up with me for so long. Your door was always open, and I am very appreciative of your continual encouragement, and helping me to keep my chin up when planned experiments turned to custard! I was fortunate enough to be out in the field with Dave Kelly when we first came across some kinky looking fish and decided to check it out further. If it wasn’t for our discoveries that day, this research would never have been undertaken. Thanks for all the fun times out in the field and your help and enthusiasm in planning my initial experiment. To the Zoology Department support staff, particularly Matthew Downs, Ken Miller, Kim Garrett, Nicky McHugh, Wendy Shanks, and Ronda Peacock; the Zoology department would be at a loss without you. I particularly want to thank Murray McKenzie for being a creative handyman genius, your flume alterations saved my experiment! A big thank you goes to the Evolutionary and Ecological Parasitology lab, particularly Kristin Herrmann, Isa Blasco-Costa and Bronwyn Preswell for your help with species identification and company in the lab. I am also indebted to Catriona Hurd and Chris Cornwall of the Botany department for allowing me to borrow their flume and helping me to set it up. To all those who helped me in the field, or gave me feedback on earlier drafts who I have not already acknowledged; Todd Beaumont, Abbey Reith, Charles Ellen, Scott Triplow, Lloyd Thomas, and Matthew Wylie (who also generously looked after my fish while I was away). A special thank you goes to Erin Forbes and Craig Preston, who not only helped with fieldwork, but without our coffee, quiz and crossword breaks, I don’t know how I would have survived the day! iv Acknowledgements I also wish to thank NIWA for presenting me with a much needed break from study. While spending time not having to think about my thesis, I was able to learn a huge amount and gain a better perspective and appreciation of my own research. Lastly, I owe a huge thanks to my parents, Briar and Lloyd. Thank you for putting up with me as a student for so long. I am forever grateful for your endless support. v Table of contents Table of contents Abstract ......................................................................................................................... iii Acknowledgements ....................................................................................................... iv Table of contents ........................................................................................................... vi List of figures .............................................................................................................. viii List of tables .................................................................................................................. ix Chapter 1: General introduction ................................................................................. 1 1.1 Parasitism as a driver of population dynamics ................................................... 2 1.2 Host parasite relationships and parasite life cycles ............................................ 5 1.3 Strategies employed by a parasite to increase the likelihood of transmission ... 6 1.4 Parasite-induced malformations ......................................................................... 6 1.5 The parasite Telogaster opisthorchis ............................................................... 10 1.5.1 Hosts of Telogaster opisthorchis...................................................................... 13 1.6 Aims and objectives ......................................................................................... 14 Chapter 2: The effect of trematode Telogaster opisthorchis on the survival and early development of Galaxias anomalus ............................................... 16 2.1 Introduction ...................................................................................................... 17 2.1.1 Aims and hypotheses ........................................................................................ 20 2.2 Materials and methods ..................................................................................... 21 2.2.1 Animal collection and care ............................................................................... 21 2.2.2 Experimental treatments ................................................................................... 22 2.2.3 Clearing and staining protocol ......................................................................... 24 2.2.4 Measures and statistical analyses ..................................................................... 25 vi Table of contents 2.3 Results .............................................................................................................. 27 2.4 Discussion ........................................................................................................ 36 2.4.5 Conclusion ........................................................................................................ 42 Chapter 3 The effect of the trematode Telogaster opisthorchis on the swimming performance of Galaxias anomalus ........................................................ 43 3.1 Introduction ...................................................................................................... 44 3.1.1 Aims and hypotheses ........................................................................................ 48 3.2 Methods ............................................................................................................ 49 3.2.1 Experimental subjects ...................................................................................... 49 3.2.2 Flume tank ........................................................................................................ 49 3.2.3 Swimming tests ................................................................................................ 51 3.2.4 Clearing and staining protocol ......................................................................... 51 3.2.5 Measures and statistical analyses ..................................................................... 52 3.3 Results .............................................................................................................. 53 3.4 Discussion ........................................................................................................ 56 3.4.1 Conclusion ........................................................................................................ 60 Chapter 4: General discussion ................................................................................... 61 4.1 Discussion ........................................................................................................ 62 4.1.1 Further research ................................................................................................ 64 4.1.2 Conclusion ........................................................................................................ 65 References ……………………………………………………………………………67 vii List of figures List of figures Figure 1.1: Malformed Oregon spotted frog (Rana pretiosa) ......................................... 8 Figure