| Summary: | 碩士 === 國立東華大學 === 海洋生物研究所 === 106 === Previous studies have shown that the synthetic estrogen 17α-ethinylestradiol (EE2) can cause endocrine disrupting effects and is environmentally stable and lipophilic. EE2 is extensively used in oral contraceptive pills, medication, cosmetics, and personal care products. EE2 has been frequently detected in coastal areas and is now considered an emerging pollutant in marine ecosystems. Agonistic behavior is crucial to individual fitness and population social structure of coral reef fish. Endocrine disrupting chemicals may disturb fish agonistic behavior and social interactions by interfering sex hormone levels. In this study, we used an experimental approach to characterize the effects of EE2 on social behavior of the false clown anemonefish (Amphiprion ocellaris) via environmental exposure. The fish were exposed to EE2 at doses of 0, 3 and 30 ng/L for 28 days. The fish from each group were randomly distributed to separate tanks to form small colonies consisting of three individuals. During the exposure, agonistic behavior, submissive response and shelter utilization were recorded with video camera weekly and quantitatively analyzed. At the end of the experiment, the 11-ketotestone (11-KT) in the plasma of the fish were measured. Our results show that EE2 exposure affected social behaviors and behavioral consistency of the fish. In the 30 ng/L EE2 group, the second-ranked fish performed more agonistic behavior toward the dominant fish, while the dominant fish responded more tremble behavior. Intra-colonial agonistic interactions also increased in the later period of the exposure. The results suggest that the ability of the second-ranked individuals to assess opponents and the intensity of aggression performed by the dominant individuals were both reduced in the EE2 group. It may cost more time and energy for the dominant fish to maintain their dominancy. Concentrations of plasma 11-KT, which is associated with social hierarchy, were also reduced in the 30 ng/L EE2 group. This study demonstrates that environmental exposure of EE2 can affect social behavior and endocrine levels in coral fish.
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