Jonathon Stillman has found that a one-inch crustacean may provide answers to one of the biggest environmental questions today: How will climate change impact natural populations of organisms?

An assistant professor of biology and the newest faculty member at Romberg Tiburon Center for Environmental Studies (RTC), Stillman studies the effects of environmental stress on porcelain crabs (Petrolisthes cintipes). His research suggests that the crabs living in the hottest habitats -- intertidal regions of tropical shores -- would not survive global warming, while closely related species living in cooler habitats -- subtidal regions of the northern cold temperate ocean -- could.

National Geographic producers found Stillman's findings so compelling that they featured him in "Strange Days on Planet Earth," a four-part television series on global warming that aired in April. Stillman appeared in the second episode, "The One Degree Factor."

"I have found that porcelain crabs living in the hottest habitats are the most heat tolerant, but they are already living very close to their thermal edge in nature," Stillman said. "They do not have the physiological capacity to adjust their heat tolerance to temperature changes of a few degrees over their normal range, such as predicted to occur during global warming."

Significant breaks could occur in the food chain if porcelain crabs, a basic source of nourishment for other species, suddenly disappeared.

During low tide periods, porcelain crabs spend their time under rocks and boulders, an environment that changes in temperature dramatically during extremely hot or cold days. Stillman tracks the fluctuations in environmental temperature in the natural habitat then duplicates these conditions in aquaria where he can measure the physiological changes that take place in the crabs.

Stillman's doctoral study work, conducted at Stanford University's Hopkins Marine Station, focused on how porcelain crabs evolve to adapt to environmental stress. At RTC, he will continue to study the physiological and molecular bases that set the thermal limits, which allow the crabs to adapt to the daily environmental fluctuations. With his students, he will study how porcelain crabs respond to thermal stress on the genomic level. The genomics project is supported by the National Science Foundation and the Joint Genome Institute in Walnut Creek.

Stillman also wants to explore the evolutionary differences between species and identify physical constraints that may make some more susceptible to climate change.

"One of the big questions we will address is what fundamental cellular mechanisms set an organism's thermal range," he said.

For more about Stillman's appearance on "Strange Days on Planet Earth," visit the PBS Web site.

-- Denize Springer
Photo: Jonathon Stillman