SAN FRANCISCO, Sept. 11 - You'd think in a river filled with anti-depressants, freshwater mussels would be, well, happy as clams. Far from it. In fact, a new laboratory study suggests that exposure to Prozac can disrupt the reproductive cycle of these mollusks, potentially increasing their risk of extinction.

The study, one of the first to examine the ecotoxicological effects of Prozac (fluoxetine) on native freshwater mussels, found that the drug caused females to prematurely release their larvae, essentially dooming them. The findings were presented today at the 232nd national meeting of the American Chemical Society, the world's largest scientific society.

"The results from this study were quite alarming," said co-investigator Rebecca Heltsley, a National Research Council Post-Doctoral Fellow at the National Institute of Standards and Technology, Hollings Marine Laboratory in Charleston, S.C. "When larvae are released too early, they are not viable, which only contributes to the problems faced by struggling populations of native freshwater mussels."

About 70 percent of the nearly 300 species of freshwater mussels native to North America are extinct, endangered or declining, according to Heltsley. In the past 100 years, no other widespread North American animal group has experienced such notable collapse, she added.

In some cases, native mussels have been crowded out by invasive species such as the zebra mussel, Heltsley said. In others, native mussels have been devastated by increased sediment loads in rivers, habitat alteration and loss, or killed off by pollutants.

"The presence of Prozac and similar drugs in U.S. rivers and streams has likely compounded the problem," Heltsley said. "It's a big concern because freshwater mussels are such an imperiled group."

Prozac, one of the nation's most prescribed anti-depressant medications, helps relieve depression by increasing the brain's supply of a neuro
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11-Sep-2006