A 300-YEAR-OLD mystery of a creature that could apparently die and come back
to life has been solved by Californian researchers.
Brine shrimp embryos called Artemia form cysts which play dead for
years before bursting into adult life. Until now, it has been impossible to find
any sign of activity in the cysts, so ever since Voltaire鈥檚 time scientists have
speculated that the embryos must stop their metabolism completely. But this
would defy one of the accepted definitions of life鈥攖hat living organisms
require a continuous expenditure of free energy. 鈥淭his is a central axiom of
biology,鈥� says James Clegg of the Bodega Marine Laboratory in California. If the
brine shrimp really did shut down totally, it was literally dying and then being
resurrected.
But now Clegg and his colleagues have detected the barest flicker of life in
baby Artemia, giving the crustaceans the slowest metabolic rate ever
measured. The researchers found a slight decrease in the amount of a chemical
called Gp4G in six-year-old embryos compared with two-and-a-half-year-old
ones.
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They think Artemia could be using Gp4G to produce ATP鈥攖he
molecule that all cells use to provide energy. They calculate that the amount of
energy produced by this mechanism would be around a ten-thousandth of a calorie
per year for every milligram of shrimp. 鈥淚t鈥檚 a teeny pilot light,鈥� says Clegg.
