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(PM281) Effects of fluoxetine on development and metamophosis in Xenopus laevis.
Rogers, Emily1, Black, Marsha1, 1 University of Georgia, Athens, GA, USA
ABSTRACT- Pharmaceuticals detected at low concentrations in surface water may have the potential to affect aquatic organisms, including developing amphibians. Our research focuses on fluoxetine, a selective serotonin reuptake inhibitor and widely prescribed antidepressant. Mammalian research indicates that fluoxetine may inhibit the thyroid axis. In larval frogs, increasing levels of thyroid hormones are necessary for metamorphosis to occur, and the presence of fluoxetine in aquatic habitats has the potential to decrease thyroid hormone levels in tadpoles, thus delaying the completion of metamorphosis. To test this hypothesis, we exposed Xenopus laevis tadpoles individually in small aquaria to fluoxetine from early development until the completion of metamorphosis. We used the following measured concentrations of fluoxetine: 0.059, 0.295, 2.95, and 29.5 ppb, which overlap concentrations detected in effluent dominated streams. Ammonium perchlorate, a known inhibitor of the thyroid axis and anuran metamorphosis was used as a positive control at 10 ppb, and FETAX solution served as the negative control. Dates of completion of forelimb emergence and tail resorbtion and were recorded for each individual, and tadpoles were measured and staged at 10-day intervals. Severe malformations were observed at all concentrations of fluoxetine tested. Malformations appeared during metamorphic climax and included stunted forelimbs and primary rotation of the hind limbs. Tadpoles exposed to 50 ppb fluoxetine exhibited impaired balance and swimming behavior. These tadpoles floated upside down at the surface of the tank and swam in circles when prodded. As this research is on-going, final times to metamorphosis are not available, but our preliminary results indicate that fluoxetine impairs normal development in X. laevis tadpoles at concentrations that may occur in the environment.
Key words: pharmaceutical, Xenopus laevis, fluoxetine, ammonium perchlorate
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