Antidepressant pharmaceuticals are widely prescribed in the United States; release of municipal wastewater effluent is a primary route introducing them to aquatic environments, where little is known about their distribution and fate. Water, bed sediment, and brain tissue from native white suckers (Catostomus commersoni) were collected upstream and at points progressively downstream from outfalls discharging to two effluent-impacted streams, Boulder Creek (Colorado) and Fourmile Creek (Iowa). A liquid chromatography/tandem mass spectrometry method was used to quantify antidepressants, including fluoxetine, norfluoxetine (degradate), sertraline, norsertraline (degradate), paroxetine, citalopram, fluvoxamine, duloxetine, venlafaxine, and bupropion in all three sample matrices. Antidepressants were not present above the limit of quantitation in water samples upstream from the effluent outfalls but were present at points downstream at ng/L concentrations, even at the farthest downstream sampling site 8.4 km downstream from the outfall. The antidepressants with the highest measured concentrations in both streams were venlafaxine, bupropion, and citalopram and typically were observed at concentrations of at least an order of magnitude greater than the more commonly investigated antidepressants fluoxetine and sertraline. Concentrations of antidepressants in bed sediment were measured at ng/g levels; venlafaxine and fluoxetine were the predominant chemicals observed. Fluoxetine, sertraline, and their degradates were the principal antidepressants observed in fish brain tissue, typically at low ng/g concentrations. A qualitatively different antidepressant profile was observed in brain tissue compared to streamwater samples. This study documents that wastewater effluent can be a point source of antidepressants to stream ecosystems and that the qualitative composition of antidepressants in brain tissue from exposed fish differs substantially from the compositions observed in streamwater and sediment, suggesting selective uptake.

Abstract-The effects of embryonic and larval exposure to environmentally relevant (ng/L) concentrations of common antidepressants, fluoxetine, sertraline, venlafaxine, and bupropion (singularly and in mixture) on C-start escape behavior were evaluated in fathead minnows (Pimephales promelas). Embryos (postfertilization until hatching) were exposed for 5 d and, after hatching, were allowed to grow in control well water until 12 d old. Similarly, posthatch fathead minnows were exposed for 12 d to these compounds. High-speed (1,000 frames/s) video recordings of escape behavior were collected and transferred to National Institutes of Health Image for frame-byframe analysis of latency periods, escape velocities, and total escape response (combination of latency period and escape velocity). When tested 12 d posthatch, fluoxetine and venlafaxine adversely affected C-start performance of larvae exposed as embryos. Conversely, larvae exposed for 12 d posthatch did not exhibit altered escape responses when exposed to fluoxetine but were affected by venlafaxine and bupropion exposure. Mixtures of these four antidepressant pharmaceuticals slowed predator avoidance behaviors in larval fathead minnows regardless of the exposure window. The direct impact of reduced C-start performance on survival and, ultimately, reproductive fitness provides an avenue to assess the ecological relevance of exposure in an assay of relatively short duration.

To reach adult habitats, juveniles of three species of Hawaiian gobies (fishes under 3 cm long) climb waterfalls up to 350 m high, over 10 000 times their body length. The demands of moving through such an extreme environment could constrain the range of viable locomotor mechanisms that these fishes use. Previous qualitative observations indicated that Lentipes concolor and Awaous guamensis use 'powerbursts' of axial undulation to climb, whereas Sicyopterus stimpsoni 'inches up' vertical surfaces by alternately attaching oral and pelvic suckers to the substrate. To compare these propulsive mechanisms and their physiological requirements, high-speed video footage of climbing by juveniles from these three species on an artificial waterfall were collected, and climbing kinematics and performance for the two climbing styles were quantified. Bouts of powerburst climbing by L. concolor and A. guamensis typically begin in or near direct water flow and are initiated by a single, rapid adduction of the pectoral fins. Powerburst climbing bouts are rapid (12.4 ± 1.0 body lengths (BL) s −1 ), but short in duration (0.07 ± 0.02 s)with few continuous locomotor cycles (3.8 ± 1.3 cycles bout −1 ). Powerburst climbers use high amplitude undulations along the entire body, but minimum resultant velocities of these undulations are high (> 6 BL s −1 ). This suggests that these species may hybridize terrestrial propulsive mechanisms with aquatic mechanisms. In contrast, climbing by inching in S. stimpsoni involves little axial undulation or fin movement. Sicyopterus stimpsoni typically exit the water outside of direct flow and seem to use terrestrial propulsive mechanisms. As the oral disc attaches to the substrate, it expands to almost twice its resting area, after which the posterior body is pulled upwards; once the pelvic disc attaches, the oral disc releases and the anterior body advances. Climbing bouts include several continuous cycles of disc attachment (11.0 ± 1.4 cycles bout −1 ) and last several seconds at velocities of 0.21 ± 0.01 BL s −1 . Before climbing waterfalls during migration to adult habitats, S. stimpsoni undergo a nonfeeding metamorphosis that leads to the development of the mouth as a secondary locomotor organ. The unusual behaviour and ontogenetic strategy of S. stimpsoni seem to be evolutionary novelties, rather than ancestral retentions, suggesting that the evolution of these features may have been closely correlated. The substantial performance and kinematic distinctions between powerburst and inching climbing indicate that considerable locomotor diversity can evolve even in the context of extreme environmental demands.

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