A laboratory study have suggested that exposure to Prozac (the commercial denomination of the active factor fluoxetine) can disrupt the reproductive cycle of the freshwater bivalves, potentially increasing their risk of extinction from natural water system. Prozac was found to cause in female freshwater mussels premature release of the larvae, practically killing them. "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," said 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".

Others factors contributing to mussels disappearance are also man made, like increased sediment loads in rivers, habitat alteration or loss and pollutants. "Prozac, one of the nation's most prescribed anti-depressant medications, helps relieve depression by increasing the brain's supply of a neurotransmitter called serotonin. But like many prescription drugs, some remnants of Prozac ultimately are mixed into wastewater that reaches rivers and streams," she completed.

Recent investigations led by a team from University of Georgia found traces of Prozac in fish and frogs and discovered that the drug slowed their development. A team from North Carolina State University placed female of a freshwater mussel species (Elliptio complanata) (photo) carrying larvae into tanks filled with water containing various concentrations of fluoxetine, ranging from 0.3 to 3,000 mg/l. These concentrations were found in surface waters of lakes and streams.

Clams were also directly exposed to serotonin. In many aquatic species, serotonin moderates the reproductive system. Within 48 hours, the mussels in both groups had released their larvae prematurely, before they were viable. In nature, this kind of contamination disrupts their reproductive cycle.

This raises the question about the effect of Prozac on other aquatic species that share similar endocrine mechanisms. "Protecting freshwater mussels and other aquatic life that are susceptible to the unintended consequences of exposure to pharmaceuticals in our rivers and streams will take a concentrated effort," Heltsley said.

"These efforts could include the development of more efficient wastewater treatment facilities that can filter out these products before they reach our waterways."

"Freshwater mussels have a key role in the ecology of rivers and streams," Heltsley emphasized.

Clams feed by filtering large volumes of water daily and, in this way, they clean the water of contaminants and excessive nutrients. Because of their way of feeding, they concentrate pollutants even when they are in low dose, serving as an early warning of water quality problems.

Bivalves are also important on the aquatic food chain, being eaten by muskrats, otters, fish and other animals.

The research team wants to collect samples from natural water systems, to compare environmental concentrations with its laboratory based study.