The ability of planktotrophic larvae to find sufficient food in the nutritionally heterogeneous marine environment has marked consequences for subsequent growth, survival and recruitment. The morphological plasticity seen in larvae of the sand dollar, Dendraster excentricus, as a response to varying food conditions represents one of the strategies used by organisms to match their growth and development to the environment. Previous research modeling energetic growth efficiencies found that D. excentricus larvae also exhibit physiological plasticity in response to different food concentrations. This previous study showed clear energetic advantages for low-fed larvae in early development that decreased rapidly and were substantially less than high-fed larvae in later development, especially in relation to protein growth efficiency (PGE) (defined as protein growth/protein ingested). Given the importance of protein metabolism in setting metabolic rates and growth-related efficiencies, my research seeks to further understand the biochemical reason for the large differences in PGE between low- and high-fed larvae (1,000 and 10,000 algal cells ml-1, respectively). In order to determine the differential rates and costs of protein synthesis in differing physiological feeding states, parallel measurements of protein synthesis, metabolic rates, and protein biomass growth were determined throughout larval development. High-fed larvae were found to have higher rates of protein synthesis compared to low-fed larvae while fractional rates of protein synthesis were not significantly different between treatments. Protein-specific rates of amino acid transport were almost 2-times higher in low-fed larvae than in high-fed. No differences were observed in either the energetic cost of protein synthesis (3.8 J (mg protein)-1) or the proportion of aerobic energy that was used to drive protein synthesis (37-42% of metabolism). Major differences, which mirrored changes in PGE with development, were observed in protein depositional efficiency (PDE). Low-fed larvae exhibited a decrease in PDE from 85% to 40% from 4 to 28 days post-fertilization while high-fed larvae increased from 55% to 65%. These differences in PDE provide a physiological explanation for the large differences in PGE between low- and high-fed larvae. Findings from this study support the idea that protein metabolism as a critical element in the developmental plasticity of larvae to differing food environments and aids in understanding, on a biochemical level, how metabolic growth efficiencies change in response to environmental factors.
|Commitee:||Pernet, Bruno, Allen, Bengt|
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 81/9(E), Masters Abstracts International|
|Subjects:||Biology, Physiology, Developmental biology|
|Keywords:||Dendraster excentricus, Growth efficiency, Larvae, Phenotypic plasticity, Physiology, Protein metabolism|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be