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Defying Depth

When you think about life’s pressures weighing down on you, consider the plight of Palaemonetes varians — the Atlantic ditch shrimp.

Smaller than a finger, and covered with only a thin shell, the translucent creature flourishes in the warm, shallow waters off the coast of northern Europe. Recently, though, scientists at the University of Southampton in England have plucked dozens of the critters from their homes and carried them to the lab, placing them in reinforced containers that replicate the crushing pressures found more than three kilometers beneath the sea’s surface. Here, where the strain of the water can squash a human’s rib cage, the shrimps survive quite happily. When the pressure’s on, this animal can sink and swim.

Scientists are subjecting the shrimps to these extreme conditions to better understand the mechanisms that allow some marine animals to adjust to life in the deep sea. Other teams are traveling to the deepest parts of the ocean — where pressure can reach more than 16,000 pounds per square inch — to study the biology of creatures that already thrive when tremendous weight bears down on them.

Exactly how deep-sea animals withstand intense pressures is not completely known, even though scientists have puzzled over this question for decades. For a long time researchers have relied on tissue samples taken from animals pulled up in nets. By comparing related proteins in shallow-water and deep-water species, researchers have found that extreme pressure can inhibit the activity of some proteins. Other studies have shown that small molecules called piezolytes may help protect proteins from the pressure.

While there is still much to be learned from tissues, the ability to bring live animals up from the deep, while maintaining their natural pressure along the way, is allowing scientists to look beyond individual molecules and study whole-body reactions. New tools designed to keep creatures alive at the surface for months will help researchers document a host of changes in the animals over time.

The work may help scientists piece together a more complete picture of how life in the ocean’s high-pressure zone survives, and how it got there in the first place, says Sven Thatje, an evolutionary ecologist at Southampton. He presented findings from his shrimp studies in Vancouver earlier this year at a meeting of the American Association for the Advancement of Science.

Evolutionary scientists believe that climate shifts at various times during Earth’s history wiped out many of the animals living in the deep sea. These extinctions were probably followed by recolonization of the dark depths by shallow-water species, which somehow were able to adapt.

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