Rahn, Anna-Katrin: Ecological and host behavioural aspects of parasite dispersal in a simple and a complex host–parasite system. - Bonn, 2018. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5n-52026
@phdthesis{handle:20.500.11811/7642,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5n-52026,
author = {{Anna-Katrin Rahn}},
title = {Ecological and host behavioural aspects of parasite dispersal in a simple and a complex host–parasite system},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2018,
month = sep,

note = {If one is to understand how parasitic diseases spread within and among host populations, one has to take into account characteristics of the given parasite species, the host as well as of their common environment. To what extent each of these three axes shapes the distribution of the parasite is determined by a range of different factors. These include the life cycle (generation time, reproductive potential), the virulence, and the transmissibility of the parasite, as well as the availability and motility of susceptible hosts, and also the suitability of the prevailing environmental conditions for the parasite and also for its (intermediate) host(s).
For this thesis, I resorted to the three-spined stickleback, Gasterosteus aculeatus, – a well-established model species – and two of its most common macroparasites – the digenean trematode Diplostomum spp. and the monogenean Gyrodactylus spp. The main aims of the first part of this work were 1) to identify potentially different barriers of migration for the stickleback host and one of its parasites with a complex life cycle – indirectly measured as population genetic structure of host and parasite – and 2) to examine water quality (particularly pH) as a potential cause of the consistently different parasite distribution in 19 natural freshwater lakes on the Scottish island of North Uist (Chapters I and II). In the second part of my thesis, I investigated host behavioural aspects of parasite distribution since grouping with infected conspecifics can favour parasite transmission to new host individuals. Chapters III and IV examine whether and in what way Gyrodactylus spp. and Diplostomum pseudospathaceum affect the shoaling behaviour of their hosts
For the population genetic analysis in Chapter I I developed new microsatellite primers specially designed for the parasite Diplostomum lineage 6. Fish-eating birds like sea gulls, whose ranges expand far across the boundaries of individual lakes, are final hosts of D. lineage 6, a common complex life cycle parasite of the North Uist sticklebacks. Confirming the paradigm that the most motile host in a parasite's life cycle significantly influences its dispersal and gene flow, no population genetic structure of D. lineage 6 was found on North Uist. For the population genetic analysis of the sticklebacks, I used previously published microsatellite primers and additionally analysed mitochondrial sequences (cytochrome b and control region) to obtain a more precise picture of the relationships among the populations. My results confirm that the sticklebacks of the individual lakes have been isolated from each other for many generations. Using field data in Chapter II I could reveal an association between the differences in parasite communities among individual lakes and the genetic differentiation between host populations (measured as pairwise FST values of the microsatellite analysis). However, I could not detect a clear influence of abiotic factors like pH on the distribution of several stickleback macroparasites. Taken together, the results of Chapters I and II suggest different levels of resistance of the stickleback populations rather than an influence of abiotic factors as potential cause underlying the consistent differences in parasite distribution on North Uist.
In Chapters III and IV I used experimental infections to examine a potential influence of the ectoparasite Gyrodactylus spp. and the endoparasite Diplostomum pseudospathaceum on the shoaling behaviour of sticklebacks. In both shoal choice experiments, infected and uninfected test fish behaved significantly differently from each other. Uninfected test fish preferred uninfected shoals compared to shoals infected with the directly transmitted Gyrodactylus spp. while Gyrodactylus-infected test fish did not show any significant preference. Surprisingly, uninfected sticklebacks preferred shoals comprising uninfected as well as infected animals over uninfected shoals while Diplostomum-infected test fish, again, did not show any significant preference. The avoidance of shoals infected with Gyrodactylus spp. might be based in a poorer physical condition. Infected animals had a lower absolute and relative body weight. To maintain an infection within a host population, Gyrodactylus spp. depends on the frequent introduction of new host individuals. To reject conspecifics infected with Gyrodactylus spp. would therefore reduce the risk of infection for uninfected sticklebacks and favour the host. D. pseudospathaceum settles in the eye lens of the stickleback and infective stages can impair the vision of its host. The preference for partially infected shoals might therefore reduce competition for healthy individuals. However, eyeflukes in my experiments were not yet infective for the bird host and had not yet cause any damage in the sticklebacks. Therefore, the results do not provide a disadvantage for the parasite.},

url = {http://hdl.handle.net/20.500.11811/7642}
}

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