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The application of DNA-based methods to the diet of Antarctic krill (Euphausia superba)


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Passmore, Abraham John 2008 , 'The application of DNA-based methods to the diet of Antarctic krill (Euphausia superba)', PhD thesis, University of Tasmania.

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Studying the diet of Antarctic krill (Euphausia superba Dana) is important for modelling the
flow of energy and nutrients through the Southern Ocean food web. Previous studies have
demonstrated that krill consume a diverse range of prey, but, have failed to detect or quantify
the contribution of important prey groups. The aim of this thesis was to examine whether
new DNA based methods can contribute to the analysis of krill diet.
Initial work developed methods for preserving, extracting and analysing prey DNA derived
from krill stomachs. These methods were shown to be capable of preserving large amounts
of intact prey DNA and generating reproducible diet data. However, two problems with the
method were identified.
The first problem was the presence of a large amount of predator DNA in diet samples that
competed with prey DNA during PCR amplification. Further work developed methods that
removed predator DNA prior to PCR, or, blocked predator DNA amplification during PCR.
These methods were successful when applied to a simplified test system but failed when
applied to real field samples.
The second problem was a discrepancy between the results obtained with DNA and
concurrent results obtained with microscopy. This suggested the initial method suffered from
bias that skewed results for some prey groups. Subsequent work attempted to resolve this
problem by changing the approach from quantifying various prey within individual krill
stomachs to quantifying the presence or absence of various prey groups in a large number
of krill. When applied to field samples this approach correctly identified the same prey groups
as microscopy, and, suggested that gastropods are a more important component of krill diet
than previously recognised. However, there were still issues regarding the quantification of
The remaining work focused on fundamental issues related to the longevity and
quantification of prey DNA in krill stomachs. In krill stomachs, prey DNA was found to: be
stable for several hours after ingestion, vary in quantity over six orders of magnitude; and,
exit the stomach faster when krill continued to engage in feeding activity. Overall the results
were promising and the application of DNA methods to krill diet warrants further

Item Type: Thesis - PhD
Authors/Creators:Passmore, Abraham John
Copyright Holders: The Author
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Copyright 2008 the Author

Additional Information:

Chapter 2 also published as: A. J., Jarman, S. N., Swadling, K. M., Kawaguchi, S., McMinn, A.
and Nicol, S. (2006). DNA as a dietary biomarker in Antarctic krill Euphausia superba. Mar
Biotechnol 8: 686-696. The final publication is available at Springer via

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