Abstract
As mental illness has increased, the levels of antidepressants in waterways are rising. The objective of this study was to determine if chronic waterborne exposure to the active ingredients in two common antidepressants fluoxetine (FLX) and bupropion (BUP) impacts loss of equilibrium (LOE) time in Gulf toadfish, Opsanus beta. LOE occurs when a fish exposed to environmental stressors, such as low dissolved oxygen, can no longer regulate their metabolism and cardiorespiratory mechanisms and lose the ability to remain upright in the water column. We hypothesize that chronic waterborne exposure to FLX and BUP will disrupt oxygen sensing and the cardiovascular and respiratory mechanisms that help to maintain metabolism and prevent LOE so that LOE time is shorter. In Series i, toadfish were exposed to FLX and BUP for 5-6 weeks: control (n=8), low FLX + BUP (nominal concentrations of 0.1 μg·L-1 FLX and 0.5 μg·L-1 BUP; n=8) and high FLX + BUP (nominal concentrations 10 μg·L-1 FLX and 50 μg·L-1 BUP, n=8). LOE tests were conducted on fish from each treatment group. In Series ii, toadfish (n=6) were exposed to hypoxia and tested for LOE and then again 7-11 days later. We hypothesize that LOE time will be lower the first time a fish is exposed to hypoxia than the second time because exposure to hypoxia will upregulate gene expression of mechanisms involved with hypoxia tolerance. There was no statistically significant effect of FLX + BUP exposure on LOE time (f =0.315, p =0.733). Interestingly, there was a significant effect of weight on LOE time (f =8.259, p =0.009). Also, fish that were previously exposed to hypoxia (50 ± 5.9 min, n = 6) have significantly higher LOE times compared to that same fish when they were naïve to hypoxia (18 ± 2.5 min, n = 6) (df=5, t=-5.33, p=0.003). Overall, hypoxia tolerance in toadfish seems to be related to weight and previous exposure to hypoxia but not to exposure to FLX + BUP.