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Behavioural responses of fish to parasitism and environmental conditions

Reynolds, Michael 2017. Behavioural responses of fish to parasitism and environmental conditions. PhD Thesis, Cardiff University.
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Every aspect of an individual’s behaviour is, to some extent, mediated by parasite exposure. Potential hosts can, for example, initiate evasive behaviours towards infected conspecifics to reduce infection risk. If infected, individuals may exhibit adaptive behavioural responses aimed at reducing pathological symptoms. In addition to infection-mediated behavioural modifications, hosts behaviourally adapt to the environment in which they reside. Disentangling the effects of parasitism from environmental variables on host behaviour can be challenging. In a series of self-contained experiments, this thesis investigates three research areas. Firstly, how thermal and hydrological environmental conditions impact freshwater host-parasite interactions; secondly, how parasite infections mediate host behavioural modifications; and finally, how such behavioural changes have population level effects with respect to social structuring. The first experiment in this thesis describes how, when presented with a range of thermal conditions, Trinidadian guppies, Poecilia reticulata Peters 1859, infected with a common monogenean ectoparasite, Gyrodactylus turnbulli Harris 1986, frequent warmer thermal conditions to self-medicate against infection (Chapter 2). In a second experiment, G. turnbulli infected guppies experiencing dissimilar flow conditions showed a significant decrease in shoaling tendencies; but only in the absence of flowing water (Chapter 3). During this experiment, infected fish were observed increasing body contact with conspecifics: a behavioural adaptation presumably aimed at offloading parasite burdens (investigated in Chapter 4). Furthermore, infected hosts exhibited nocturnal restlessness, which may have further repercussions for host health (Chapter 5). Finally, parasite-mediated host behavioural modifications had significant population level effects with respect to social structuring. G. turnbulli infected guppies significantly increased their social rank within a population and instigated more contacts than they received, in contrast to their uninfected counterparts (Chapter 6). The infection status of an individual therefore determines its significance in mediating a population’s social dynamics, and so driving disease transmission processes.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Biosciences
Date of First Compliant Deposit: 16 January 2018
Date of Acceptance: 16 January 2018
Last Modified: 30 Jan 2019 02:30

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