Larval forms are dominant in the life history strategies of invertebrates in marine environments. In Antarctica, energy budget calculations have shown that larval stages of echinoderms have the capacity to survive without food for periods of several months to years. This has led to the speculation that mechanisms of energy metabolism are more efficient in these larval forms, and that this "enhanced efficiency" might be unique to life in extreme cold. Recent studies on the biochemical bases of developmental physiology in Antarctic marine invertebrates have revealed some novel aspects of metabolism in the cold. Contrary to expectations of low metabolism and low rates of macromolecular synthesis in the cold, embryos and larvae of an Antarctic sea urchin have high rates of protein synthesis, while maintaining low rates of metabolism. This apparent paradox was resolved with the recent finding that the cost of protein synthesis in this Antarctic sea urchin is one twenty-fifth of that reported for other animals. This is the highest efficiency for protein synthesis reported for an animal and has important implications for the physiology of growth and development in cold environments. This unique biochemical efficiency of protein synthesis in the cold is the subject of detailed investigation in the current project. The research team will combine expertise in Antarctic larval physiology and biochemistry and molecular biology of sea urchin development to address an experimental plan that is based on three major objectives. (1) The generality of the recent finding of the low cost of protein synthesis in Antarctic sea urchin larvae will be tested by measuring metabolism and protein synthesis during development of other Antarctic echinoderm species. (2) The prediction of a high rate of protein synthesis with low metabolic cost is that growth efficiencies will be high in such organisms. This will be tested by measuring the physiology of protein growth efficiencies in larvae. (3) The unique high efficiency of protein synthesis in Antarctic sea urchin embryos will be studied using specific molecular biology approaches. The combination of these quantitative analyses will enable us to pinpoint those aspects of protein metabolism that result in such extremely high energy-efficiencies. Understanding metabolic efficiency in polar organisms is required to help resolve long-standing questions regarding temperature compensation and adaptations to food limitation in polar regions. The unique approach here is the emphasis on the cellular and sub-cellular levels of biological analysis to understand the relationship among development, growth, metabolic rate, and rates and costs of protein synthesis in the Antarctic organisms we propose to study.
