A DNA-based method for identification of krill species and its

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application to analysing the diet of marine vertebrate predators

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stron

6590

ID

Australian Antarctic Division

2002

rok

Abstract

Accurate identification of species that are consumed by vertebrate predators is necessary for

understanding marine food webs. Morphological methods for identifying prey components after

consumption often fail to make accurate identifications of invertebrates because prey morphology

becomes damaged during capture, ingestion and digestion.

Another disadvantage of morphological methods for prey identification is that they often involve

sampling procedures that are disruptive for the predator, such as stomach flushing or lethal

collection. We have developed a DNA-based method for identifying species of krill (Crustacea:

Malacostraca), an enormously abundant group of invertebrates that are directly consumed by many

groups of marine vertebrates. The DNA-based approach allows identification of krill species

present in samples of vertebrate stomach contents, vomit, and, more importantly, faeces. Utilizing

samples of faeces from vertebrate predators minimizes the impact of dietary studies on the

subject animals. We demonstrate our method first on samples of Adelie penguin (Pygoscelis

adeliae) stomach contents, where DNA-based species identification can be confirmed by prey

morphology. We then apply the method to faeces of Adelie penguins and to faeces of the

endangered pygmy blue whale (Balaenoptera musculus brevicauda). In each of these cases, krill

species consumed by the predators could be identified from their DNA present in faeces or

stomach contents.