Brainy genes, not brawn, key to success on mu...( It's hard being a mussel: you have t...)

It's hard being a mussel: you have to worry about hungry starfish and even hungrier humans, not to mention an environment that can change your body temperature 50 degrees Fahrenheit in just a few hours.

"It's one of the most variable habitats on Earth," said USC biologist Andrew Gracey. "Mussels can spend part of the day bathed in cool Pacific seawater and the other part baked under the California sun."

Gracey led the first real-time molecular sampling of mussels in their natural habitat, the results of which appear online Oct. 9 in the journal Current Biology.

The researchers found that the hardy mollusks alternate between expressing genes associated with eating and genes associated with growing.

Scientists have thought that mussels survive their harsh home on the rocks by just being tough, but this study suggests a more sophisticated strategy.

"They spend part of the day respiring, and doing metabolic processes, and then the other part of the day switching to cell division," Gracey explained.

Because their environment is so unpredictableat low tide mussels could scorch on a sunny day and get soaked on a stormy onethese regular cycles were unexpected.

"To be honest, I first thought they'd be wasting their time to be constantly switching on this gene and switching off that gene," Gracey said.

The scientists also found that as the environment became harsherlike higher up the rocksthe oscillations in gene expression became more pronounced.

In addition to cyclic expression, the study found that mussels use two sets of genes to respond to heat stresssometimes reacting to temperature changes in seconds.

"Day-in, day-out, they switch on a particular set of genes associated with routine heat stress, but when the day got very hot we saw this other battery of genes dealing with really extreme temperatures," Gr
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