Adaptive Significance of a Small Heat Shock/a-Crystallin Protein (p26) in Encysted Embryos of the Brine Shrimp, Artemia franciscana*

among the most resistant of all animal life history stages to extremes of environ-mental stress. This resistance has likely been acquired during evolutionary adap-tation to their harsh ecological setting. In the laboratory, for example, some of these embryos survive more than 6 years of continuous anoxia while fully hydrated and at room temperature, a phenomenal capability that can easily be related to their frequent encounters with anoxic conditions in nature. A small heat shock protein belonging to the a-crystallin family of proteins, referred to as p26, appears to play a central role in the stress resistance of these embryos. Our evidence shows that this protein is an important component in their adaptive repertoire, and vital for the survival of Artemia in nature