The Effects of Fluoxetine on Daphnia magna Wound Melanization, Reproduction, and Heart Rate

Pollution of freshwater ecosystems by pharmaceuticals, and drug metabolites, is an area of significant concern. Pharmaceuticals can pollute waters through manufacturer waste products, improper disposal of medications, and by humans excretion of medications.The purpose of this study was to determine the effects that an environmentally-relevant concentration (1 μg/L) of fluoxetine (Prozac), a commonly prescribed Selective Serotonin Reuptake Inhibitor (SSRI), has on Daphnia magna wound melanization, reproduction, and heart rate. D. magna, a small freshwater invertebrate, have been shown in early studies to respond to fluoxetine, and are a demonstrated good invertebrate model organism. The present study had two groups of D. magna, a control group and a group exposed to fluoxetine. After an exposure period (48 hours), D. magna were wounded on the carapace with a small needle, imaged and imaged again at 24 hours and 7 days. Heart beats per minute were quantified through video microscopy, and wound melanization at 24 hours was used as a proxy for cellular wound response. We found that wounds exhibited robust wound melanization at 24 hours, and clearing of melanization by 7 days. Fluoxetine exposure did not have significant effects on heart rate. D. magna that were exposed to fluoxetine had higher levels of wound melanization than those in the control group; however, the differences were not significant. Our results reveal general cellular dynamics of wound healing in D. magna, which may be conserved across other members of the Order.