林鼠如何对付植物毒素

Life is tough for woodrats in deserts of the U.S. Southwest. There are few plants for food, and those plants produce poison to deter¹ rodents²（啮齿动物） , insects and other animals. A new University of Utah study shows how certain woodrats put themselves on a diet to avoid poisoning: They sample a smorgasbord（大杂烩） of toxic³ plants, eat smaller meals, increase time between meals and drink more water if it is available. #

"For decades, we have been trying to understand how herbivores（食草动物） deal with toxic diets," says biology Professor Denise Dearing, senior author of the study, published online Tuesday, Aug. 9 in the British Ecological⁴ Society's journal Functional⁵ Ecology.

"This study compares woodrats that eat only a single plant – juniper – with another species that eats several kinds of plants, including a small amount of juniper," Dearing says. "We were trying to understand how they regulate the dose of toxic chemicals they eat by observing how often and how much they ate." #

"We found that the woodrat that eats many types of plants was better at limiting toxin⁶ intake⁷ than the woodrat that eats only juniper," she adds.

The "specialists" – woodrats that eat only juniper – have evolved liver enzymes⁸ to metabolize large amounts of juniper toxins⁹, so they did not change the amount of juniper they ate and did not drink more water. But "generalists" – woodrats that can metabolize small amounts of many different plant toxins – actually changed their eating and drinking behavior to avoid an excessive dose of any one plant poison. #

Dearing conducted the research with first author and Utah biology Ph.D. student Ann-Marie Torregrossa – who now is a postdoctoral fellow at Florida State University – and Anthony Azzara of Bristol-Myers Squibb in Princeton, N.J. The research was funded by the National Science Foundation and the American Museum of Natural History.