We document phototactic responses in different amphipod populations of Gammarus minus, Stygobromus tenuis, and Crangonyx shoemakeri, each collected at 2–3 sites within the Washington DC area. We then assessed how baseline phototaxis was altered following either short-term (3-week) or long-term (6-week) exposure to 0.05 µg/L or 0.5 µg/L fluoxetine. Our results classify all species as significantly photonegative, a response that depended solely on the presence, not quality, of light. Short-term fluoxetine exposure caused some animals to become photoneutral, regardless of concentration, while others remained photonegative. Long-term exposure to 0.5 µg/L fluoxetine caused photoneutral behaviors in all surviving populations; exposure to 0.05 µg/L had variable effects. These differential effects were due to a significant effect of population/sampling location on photobehavior. Overall, these results identify species-specific effects of chronic fluoxetine exposure and underscore how the response to light in 7 geographically distinct populations is uniquely tuned to requirements for survival.

我们记录了Gammarus minus、Stygobromus tenuis和Crangonyx shoemakeri的不同端足类群的趋光反应，每个都在华盛顿特区的 2-3 个地点收集。然后，我们评估了在短期（3 周）或长期（6 周）暴露于 0.05 µg/L 或 0.5 µg/L 氟西汀后基线趋光性如何改变。我们的结果将所有物种都归类为显着负光性，这种反应仅取决于光的存在，而不是光的质量。短期氟西汀暴露导致一些动物变得光中性，无论浓度如何，而其他动物仍然是光负性的。长期暴露于 0.5 µg/L 氟西汀会导致所有幸存人群出现光中性行为；暴露于 0.05 µg/L 会产生不同的影响。这些不同的影响是由于人口/采样位置对光行为的显着影响。全面的，