Meeting Abstract
Previous research from our lab modeling energetic growth efficiency in larvae of the sand dollar, Dendraster excentricus, has shown that large-scale physiological plasticity occurs in concert with morphological plasticity during larval development in response to different food rations (1,000 and 10,000 algal cells ml-1). In particular, low-fed larvae had higher protein growth efficiency (PGE, protein grown standardized to protein ingested) than high fed larvae early in development, but this advantage diminished rapidly and in later development, fell below that of high fed larvae. Given the importance of protein growth in planktotrophic larval development, we sought to further understand these large differences in PGE by measuring rates, costs, and efficiencies of protein metabolism in low- and high-fed larvae. While low- and high-fed larvae had similar mass-specific rates of protein synthesis, amino acid transport rates were almost 2-times higher in low-fed larvae. No differences were observed in either the energetic cost of protein synthesis (~ 5 J (mg protein)-1) or the proportion of aerobic energy that was used to drive protein synthesis (~40% of metabolism). Major differences, which mirrored changes in PGE with development, were observed in protein depositional efficiency (PDE, protein growth standardized to protein synthesized). 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. These results demonstrate that protein metabolism is a critical response element in the developmental plasticity pathway of larvae experiencing different food environments.
