High macromolecular synthesis with low metabolic cost in Antarctic sea urchin embryos

Assessing the energy costs of development in extreme environments is import ant for understanding how organisms can exist at the margins of the biosphe re. Macromolecular turnover rates of RNA and protein were measured at -1.5 degreesC during early development of an Antarctic sea urchin. Contrary to e xpectations of tow synthesis with tow metabolism at low temperatures, prote in and RNA synthesis rates exhibited temperature compensation and were equi valent to rates in temperate sea urchin embryos. High protein metabolism wi th a tow metabolic rate is energetically possible in this Antarctic sea urc hin because the energy cost of protein turnover, 0.45 joules per milligram of protein, is 1/25th the values reported for other animals.