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Investigation of the Factors Affecting the Population Dynamics of Captive Partula Snails. Ana Rita Peres Cardoso Gouveia Department of Life Sciences, Division of Biology, Silwood Park Campus, Ascot, Berkshire, SL5 7PY, U.K. A thesis submitted for the degree of Doctor of Philosophy Imperial College London 2011 Abstract Partula snails, also known as Polynesian tree snails, were first recorded scientifically from Captain Cook‟s voyage 236 years ago. They are small gastropod molluscs which belong to the order Stylommatophora. Their distribution is focused in the Pacific region where the majority of the species are island endemics. Half the species are found in the Society Islands of French Polynesia where most research has been carried out. Wild populations were almost annihilated following the introduction of a predatory snail, Euglandina rosea, to control the introduced giant African land snail (Lissachatina fulica) which had become an agricultural pest affecting the local economy. In 1987 the Partula Propagation Group (PPG) initiated a worldwide captive breeding programme for Partula snails in an attempt to save them from extinction. In captivity, though, episodes of high mortality have led to the extinction of some species. The causes of these declines are as yet uncertain. This study aimed to investigate the factors that have affected the survival of 15 species (including two subspecies) of Partula snails in captivity. In summary, the results indicate that both environmental factors (temperature, relative humidity and light) and diet (calcium concentration and dog and cat vitamins in the diet) significantly affect the population dynamics of Partula snails. Both excess light and unstable temperatures and humidity had detrimental impacts on the survival and reproductive success of the species. Additionaly, the low concentration of calcium and the addition of dog and cat vitamins in the diet are also significantly detrimental on the survival and reproductive success of Partula gibba. These studies are highly significant because the biology and requirements of Partula snails‟ are poorly understood, and this can jeopardise a successful captive breeding programme and future reintroductions into their natural environment. It is imperative that the factors that have affected the survival rates of snails in captivity for the last 25 years are fully understood. Partula snails face an uncertain 2 future, with the mass mortality episodes observed during the years several species were lost. It is hoped that these findings stimulate further research in this area and can be applied to other species in similar circumstances. 3 Declaration The work presented in this thesis is entirely my own, and any other material is accordingly referenced. Ana R. P. C. Gouveia 4 Acknowledgements First and foremost I want to express my gratitude to all the people who helped and supported me through these years. I would like to thank everybody who was important to the successful realization of this thesis, as well as expressing my apology for those I do not mention. In the first place I would like to record my gratitude to my supervisors Simon Leather and Donald Quicke for their enthusiastic supervision, understanding, advice and guidance during my PhD. I also want to express my gratitude to Paul Pearce-Kelly who has supported and cared for me since the moment we met. Above anything he has been the best friend I could ask for. I wish to gratefully acknowledge Professor Elizabeth Cunning, Professor Bryan Clarke, Professor Tim Coulson, Professor Mick Crawley, Dr. Tilly Collins, Dr. Daniel Reuman, Dr. Nils Bunnefeld, Dr. Joaquin Hortal, Dr. Arpat Ozgul, Dr. Navinder Singh, Dr. David Hunt, Dr. Barbara Ritchie, Dr. Jake Bundy, Dr. Mike Wilson and anyone else who contributed directly or indirectly to this thesis with advices, ideas, comments and suggestions. A special thanks to Romain Pizzi, Professor Mark Fox and Dr. Sergei Spiridonov. And also thanks to my panel (Dr. Sally Power and Dr. Rob Ewes) who gave me valuable suggestions and constructive criticism. I am indebted to Dr. Trevor Coote and Shaheed Macgregor for their wise, comforting words as well as valuable technical advice and the help they provided, with thanks also to the “Bugs Team” at London Zoo. 5 I want to express my thanks to the Silwoodian staff (technicians, cleaners, electricians the security team, the ICT team etc). Without them this could not be accomplished, in particular Diana Anderson, Christine Short, Paul Nicholas, Paul and Jim, Taru, Catherine, and John all of them, in different ways helped me during these years either with comforting and friendly words and/or with technical advice providing a stimulating and friendly environment to work in. My Silwoodian and non-Silwoodian friends deserve a place in this pages since they helped me in the up and down emotional stages of the PhD, they prevented me from losing my sanity and also gave me valuable advices, I have no words to express how much they actually helped me, I probably never told them but Ana and Joaquin, Arpat, Navinder, Manju, Francesca and Eva, Ana, Oriana, Ambika, Marcia, Diego, Jenifer, Lena, Catarina, Paula, Tania, Carla, and particularly Telmo, Claudia Nunes and Parreira, Angela and Nelson, Bertinho and Vanessa, thank you so much for being always there when I needed you. I wish express my gratitude and deep appreciation to Martin MacDowell he dried my tears several times, he gave me encouragement, emotional support and all the love one needs to overcome the rough times, and showed me that there was a light at the end of the tunnel. Thank you for your love, support and putting up with my grumpiness and also thank you for providing me with a fun relaxing and fantastic environment to live in. I have no words to express my appreciation to my family whose dedication, love and belief, has given me the confidence and strength to get this far. I was extraordinarily fortunate in having them always by my side supporting my decisions and advising me. My mum and dad always motivated and supported me to pursue an intellectual and academic future. I want to thank them for raising me with buckets of love and laughter for which my two brothers also 6 contributed a big deal. I wish to thank my father and mother for all the sacrifices they went through to provide me with the chances and fantastic life I had so far. A special thanks to Nuno and Gonçalo for being the best friends and siblings I could ask for. Lastly, and most importantly, to them, my parents and brothers I dedicate this thesis. Gould, (1993) “this essay is a story of genocide in paradise, a preventable wholesale slaughter, just completed in one human generation. You do not know the tale only because it pitted snail against snail, rather than man against man” 7 Contents Pages Abstract 2 Declaration 3 Acknowledgements 4-6 Contents 7-9 List of Tables 10 List of Figures 11-13 Chapter 1. General Introduction 14-37 1.1. Partula snails 14, 16 1.2. The species and their natural habitat 17-27 1.2.1. Tahitian species 19-21 1.2.1.1. Partula affinis 19 1.2.1.2. Partula clara 20 1.2.1.3. Partula hyalina 20 1.2.1.4. Partula nodosa 21 1.2.2. Species of the Mariana Islands, Guam and Saipan 21, 22 1.2.2.1. Partula radiolata 22 1.2.2.2. Partula gibba 22 1.2.3. Species of Moorea 22-24 1.2.3.1. Partula tohiveana 23 1.2.3.2. Partula mooreana 23 1.2.3.3. Partula suturalis strigosa and P. s. vexillum 23, 24 1.2.3.4. Partula taeniata nucleola and P. t. simulans 24 1.2.4. Species of Raiatea and Huahine 25, 26 8 1.2.4.1. Partula faba 25 1.2.4.2. Partula tristis 25, 26 1.2.4.3. Partula hebe bella 26 1.2.4.4. Partula varia 26 1.2.5. Futuna and Alofi species 26, 27 1.2.5.1 Partula subgonochila 27 1.3. Wild populations 27, 28 1.4. Captive breeding programmes 29, 30 1.5. Population collapses and diseases 30, 31 1.6. Environmental 31, 32 1.6.1. Temperature and Humidity 31 1.6.2. Light 32 1.7. Diet 32, 33 1.8. And the story repeats 34 1.9. Thesis outline 35-37 Chapter 2. Effects of different calcium concentrations added to the diet of Partula gibba (Férussac) on morphometric growth parameters, weight and reproductive success. 38-51 2.1. Abstract 38 2.2. Introduction 39, 40 2.3. Methods 40-42 2.4. Results 43-48 2.5. Discussion 49, 51 9 Chapter 3. Investigation of the effect of vitamin supplement added to the diet of Partula snails. 52-60 3.1. Abstract 52 3.2. Introduction 53-56 3.3. Methods 56, 57 3.4. Results 57, 58 3.5. Discussion 59, 60 Chapter 4. Investigating the effects of environmental stress on the population dynamics of endangered Partula snails. 61-77 4.1. Abstract 61 4.2. Introduction 62, 63 4.3. Methods 64-66 4.4. Results 67-74 4.5. Discussion 75-77 Chapter 5. Investigation into the role played by light intensity on the behaviour, reproduction and mortality of Partula snails. 78-86 5.1. Abstract 78 5.2. Introduction 79-81 5.3. Methods 81-83 5.4. Results 83, 84 5.5. Discussion 85, 86 Chapter 6. General Discussion 86-90 References 91-111 Appendix 112-120 10 List of Tables Tables Pages Table 2.1. Linear model summary, for Partula gibba morphometric measurements and reproductive success against the addition of calcium 47 to the diet. Table 4.1.
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