Impacts of within-alga distribution of nitrogen and defense compounds on the consumption of the giant kelp (Macrocystis pyrifera) by brown turban snails (Chlorostoma brunnea)
Abstract/Contents
- Abstract
- In marine environments, grazing by invertebrate herbivores exerts a powerful influence on benthic macro-algae, such as the commercially and ecologically important giant kelp, Macrocystis pyrifera. Optimal defense theory (ODT), originally derived from observations of terrestrial plants, postulates that more (metabolically costly) defensive chemical compounds are preferentially allocated to protect tissues of high fitness value and vulnerability, especially meristematic and reproductive tissues, compared to other tissues, such that the overall fitness of the organism is optimized. For example, among vegetative tissues, younger and more productive tissues should be better defended than senescent ones. Defenses are expected to reduce herbivores' preference for well-defended tissues and, through reduced digestibility, to slow the growth of herbivores feeding on them. This study, conducted in Monterey, California, evaluates whether M. pyrifera employs a chemical defense strategy consistent with ODT and explores the impacts on an abundant kelp herbivore, the brown turban snail, Chlorostoma brunnea. Levels of Nitrogen and polyphenolic defense compounds were measured in four tissue types: apical meristems and reproductive sporophylls, as well as mature and senescent blades. Snail feeding preference between the tissue types were evaluated as well as growth rates on exclusive diets of each. Results matched the predictions of ODT only in part. Apical meristems indeed had elevated concentrations of polyphenols and were less preferred in herbivore feeding trials. The senescent blades were, as expected, the preferred tissue for snails. However, sporophylls had low levels of polyphenols and were preferred by snails over mature blades and yielded the greatest growth rate. Moreover, there were no differences in preference between mature blades and apical meristems. Finally, levels of polyphenols and Nitrogen do not fully explain the results within an ODT framework and it seems likely that additional defense mechanisms and nutritional interactions remain to be investigated in the relationship between giant kelp and its herbivores.
Description
| Type of resource | text |
|---|---|
| Date created | May 2012 |
Creators/Contributors
| Author | Markham, Ian |
|---|---|
| Primary advisor | Micheli, Fiorenza |
| Advisor | Dirzo, Rodolfo |
Subjects
| Subject | Macrocystis pyrifera |
|---|---|
| Subject | optimal defense theory |
| Subject | ODT |
| Subject | Chlorostoma brunnea |
| Subject | giant kelp |
| Subject | brown turban snail |
| Subject | polyphenolic defense compounds |
| Subject | Stanford Biology Department |
| Genre | Thesis |
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Preferred citation
- Preferred Citation
Markham, Ian (2012). Impacts of within-alga distribution of nitrogen and defense compounds on the consumption of
the giant kelp (Macrocystis pyrifera) by brown turban snails (Chlorostoma brunnea). Stanford Digital Repository. Available at: http://purl.stanford.edu/xj391jk5611
Collection
Hopkins Marine Station of Stanford University Honors Theses
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