No document available.
Abstract :
[en] The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS), with his chemical structure similar to thyroid hormones (THs), may have adverse effects on the thyroid system. The study we carried out aims to evaluate the effects of TCS exposure on development of Cyprinodon variegatus, a fish model used in ecotoxicological studies. We investigated the potential effects of TCS on C. variegatus during two key periods; embryonic development and metamorphosis. We exposed eggs and larvae to environmental relevant concentrations. We showed that TCS had no effect on reproduction parameters, such as egg fertility or survival rate of larvae. However, we highlighted the fact that hatching of exposed larvae was delayed of around 6 to 13 hours compared to control embryos. During the larval phase, measurements of THs levels were performed. We showed that TCS affected the typical ontogenic variations of the whole body thyroid hormones concentrations during metamorphosis. As THs are known to control somatic growth and development, we tested the effects of TCS exposure on morphological development. We observed no deformity or malformation, but we revealed a developmental retardation in larvae exposed to TCS, of around 18 to 32 hours. Such a developmental delay had never been highlighted in previous studies on TCS exposed fish. We hypothesize that the disruption of THs homeostasis affects the timing of the start of metamorphosis. As a consequence, exposed larvae showed an extended larval phase compared to the control group. The harmful effects of TCS on physiology and development are a major concern, as marine organisms are constantly exposed to it. Furthermore, strong connections exist between thyroid and reproductive system, which might have deleterious effects on population dynamics.
