GINSBURG, D.W.; MANAHAN, D.T.: Biochemical bases of metabolic intensity during sea urchin development

Early stages of development require increased oxygen consumption to support energetically demanding processes, such as rates of protein synthesis and maintenance of ion gradients in the increasing number of cells. Little is known about the relationship among these physiological processes and their role in setting metabolic rates during embryonic and larval development. We measured respiration and rates of protein turnover during development of the purple sea urchin, Strongylocentrotus purpuratus. After gastrulation there was a 3-fold increase in respiration rate and, hence, metabolic intensity as there is no increase in mass for these prefeeding stages. From the gastrula to the feeding pluteus larval stage, the cost of protein synthesis ranged from 10 to 34% of total aerobic metabolism for the period of development studied. Combining our data with previously published rates of ATP utilization by the sodium pump in vivo for S. purpuratus, we calculated metabolic ‘pie-charts’ for different stages of development. Between 45 and 72% of respiration could be accounted for by protein synthesis and the sodium pump. In larvae, for example, a total of 61% of respiration was accounted for solely by protein synthesis (22%) and the sodium pump (39%). These findings suggest that all of the other biological processes in sea urchin larvae – swimming, feeding, digestion, macromolecular (non-protein) biosynthesis etc. – must fit into the remaining 39% of their total energy budget.