All animals interact in some way with microbes during their growth and development. These interactions often prove harmful as animals find themselves exposed to pathogens or the harmful by-products of microbial growth. For many animals avoidance of microbes is difficult or impossible, particularly for species that obligately utilise microbe-laden resources during reproduction. Larvae of the carrion beetle Nicrophorus vespilloides are significantly harmed by the bacteria they encounter during their development on decomposing vertebrate carcasses. However, these effects can be partially ameliorated by parental investment into behaviours which reduce the effects of microbial exposure. In this thesis I focus on two aspects of N. vespilloides response to microbial competition. First I investigate the composition and fitness effects of the application of exogenous secretions by parents and larvae to their breeding resource. This behaviour in parents has long been hypothesized to form an important part of the antimicrobial component of parental care, but this has not been rigorously tested. Nor, prior to my work, has any experimental attention been given to the possibility that larvae also contribute to antimicrobial production while on the carcass. Second I investigate the late-life and intergeneration effects of microbial exposure during development on a range of beetle life history traits including larval body size, brood size and immune function and survival in response to bacterial challenge. My results demonstrate the following: i) that larval N. vespilloides suffer significant harm from microbial competition during development that manifests itself in several ways, e.g. reduced body size, increased susceptibility to infection, or reduced ability of mothers to provide post hatch maternal care; ii) that the effects of microbial competition can be mitigated by parental behaviours that reduce the level of microbial contamination on a resource. Specifically, mothers apply antimicrobial secretions containing lysozyme to the carcass which kills bacteria and significantly increases larval survival; iii) that larvae are not totally reliant on their parents for antimicrobial protection because they too can secrete exogenous antimicrobial compounds similar in activity to their parents and which significantly increase larval fitness; iv) the effects of microbial competition can result in transgenerational effects that reduce offspring fitness but which can also provide context-dependent benefits by increasing larval survival when post-hatch parental care is poor and following challenge with pathogenic infection. By developing on and consuming carrion Nicrophorus larvae and other specialist scavengers experience an extreme example of the challenges faced by opportunistic carrion users or animals that for any reason utilise microbially contaminated resources. This makes them ideal model organisms to study adaptations to the presence of complex microbial communities that may contain both pathogens and toxin producers.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:626879 |
| Date | January 2013 |
| Creators | Arce, Andres |
| Contributors | Preziosi, Richard; Rozen, Daniel |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/inter-kindgom-competition-for-rare-and-ephemeral-resources(4b761162-dc07-4704-968f-d1119d5ea725).html |
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