The comic-book ads for sea monkeys were always enticing. Drawings showed amazingly humanlike creatures cavorting underwater. Sea monkeys, the ads said, were playful and trainable; and they could be yours for just a few dollars. If you sent away for them, you may have been disappointed to find that your instant pet didn’t resemble any kind of monkey you’d ever seen. But sea monkeys--also known as Artemia franciscana, or brine shrimp--perform at least one legitimately amazing trick: they can live for years without oxygen. Investigating this feat, James Clegg, a biochemist at the University of California at Davis, took dried-up A. franciscana embryos and rehydrated them in oxygen-free water (in other words, he hatched sea monkeys). Without oxygen, the embryos looked dead. And yet when Clegg exposed the embryos to oxygen four years later, some 60 percent resumed normal development. Clegg suspects that a class of proteins called molecular chaperones, which protect other proteins from degrading, may be responsible for the shrimps’ impressive resilience. He kept the not- quite-dead embryos at room temperature all those years; if the temperature were a few degrees cooler, Clegg suspects, they might last for decades.