Meeting Abstract
Larvae of the sand dollar, Dendraster excentricus, have significant morphological plasticity when reared at different food concentrations. Our lab has recently observed that D. excentricus larvae also exhibit physiological plasticity in response to food levels. While high-fed (10 cells ul-1) larvae grew and developed faster than low-fed larvae (1 cell ul-1), they also possessed higher protein growth efficiency (PGE = protein deposited/protein ingested). This study seeks to understand the biochemical attributes of this phenomenon by determining the rates and costs of protein synthesis in low- and high-fed larvae of D. excentricus. Rates of synthesis were 1.4 ng protein hr-1 larvae-1 at 3 days post-fertilization (DPF). At 7 DPF (4 days after initiation of feeding) rates were 0.47 and 1.13 ng protein hr-1 larvae-1 for low- and high-fed larvae, respectively. By 27 DPF respective rates increased to 1.68 and 11.6 ng protein hr-1 larvae-1. Fractional rates (% of total protein pool synthesized per hour) were similar between low- and high-fed larvae at ~ 0.5 % hr-1. Preliminary analysis returned an energetic cost of synthesis that was independent of ration level and similar to other larval echinoderms at ~ 10 J/(mg protein synthesized). Results are further discussed in the context of depositional efficiency and its relationship to PGE. The energetic and biochemical analyses conducted in the study are important for determining if and how the cost and regulation of protein metabolism differs between larvae experiencing different food conditions. Such data will allow for a more mechanistic understanding of how environmental conditions determine larval survival and recruitment
