Transient exposure to environmental estrogen affects embryonic development of brown trout (Salmo trutta fario)

Transient exposure of brown trout embryos from fertilization until hatch (70 days) to 17-estradiol (E2)was investigated. Embryos were exposed to 3.8 and 38.0 ng/L E2 for 2 h, respectively, under four scenar-ios: (A) exposure once at the day of fertilization (0 days post-fertilization, dpf), (B) once at eyeing stage(38 dpf), (C) weekly exposure until hatch or (D) bi-weekly exposure until hatch. Endpoints to assess estro-gen impact on embryo development were fertilization success, chronological sequence of developmentalevents, hatching process, larval malformations, heart rate, body length and mortality. Concentration-dependent acceleration of development until median hatch was observed in all expo-sure scenarios with the strongest effect observed for embryos exposed once at 0 dpf. In addition, thehatching period was significantly prolonged by 4–5 days in groups receiving single estrogen exposures(scenarios A and B). Heart rate on hatching day was significantly depressed with increasing E2 concen-trations, with the strongest effect observed for embryos exposed at eyeing stage. Estrogenic exposure at0 dpf significantly reduced body length at hatch, not depending on whether this was a single exposureor the first of a series (scenarios A and D). The key finding is that even a single, transient E2 exposure during embryogenesis had significanteffects on brown trout development. Median hatch, hatching period, heart rate and body length at hatchwere found to be highly sensitive biomarkers responsive to estrogenic exposure during embryogenesis.Treatment effects were observable only at the post-hatch stage.