Cool Crabs Take the Heat

Biologists find that some warm-weather species can't take global warming's heat

10-01-2003 // Laura Tangley

FROM THE POLES to the equator, many plant and animal species are expected to suffer as the planet continues heating up. Though one might expect that species adapted to warmer habitats will fare better, the results of a new study published in Science contradict this logical assumption.

In research conducted at Stanford University’s Hopkins Marine Station in Pacific Grove, California, biologist Jonathon Stillman looked at how well four species of inch-long porcelain crabs—two species that inhabit chilly coastal Oregon and two from warm waters off Puerto Peñasco, Mexico—adapted to the increases in water temperature scientists are predicting over the next century. After acclimating the animals to the temperatures they are accustomed to in the wild, he gradually turned up the heat to see what would happen.

"The results were surprising," says Stillman. By altering their upper thermal tolerance limits, it turned out that the cold-water crabs acclimated better than those from warmer climes. The top survivor, in fact—Oregon’s Petrolisthes eriomerus—hailed from the coolest habitat of all.

The explanation could be "an evolutionary trade off," suggests Stillman. "To survive really high temperatures in the summer, the southerners have given up their ability to adjust their thermal limits," making them even more vulnerable to global warming than their cool-water cousins.

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