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Polybrominated diphenyl ethers (PBDEs) have the potential to disrupt the thyroid endocrine system. The objective of the present study was to characterize the disrupting effects of longterm exposure on the thyroid endocrine system in adult fish and their progeny following parental exposure to PBDEs. Zebrafish (Danio rerio) embryos were exposed to environmentally relevant concentrations (1, 3, and 10 μg/L) of the PBDE mixture DE-71 for 5 months until sexual maturation. In the F0 generation, exposure to DE-71 significantly increased plasma thyroxine (T4) but not 3,5,3 0 -triiodothyronine (T3) in females. This increased T4 was accompanied by decreased mRNA levels of corticotropinreleasing hormone (CRH) and thyrotropin β-subunit (TSHβ) in the brain. The F1 generation was further examined with or without continued DE-71 treatment conditions. Exposure to DE-71 in the F0 fish caused significant increases in T4 and T3 levels in the F1 larvae and modified gene expressions in the hypothalamicÀ pituitaryÀthyroid axis (HPT axis) under both conditions. Decreased hatching and inhibition of growth in the F1 offspring were observed in the condition without DE-71 treatment. Continued DE-71 treatment in the F1 embryos/larvae resulted in further decreased hatching, and increased malformation rates compared with those without DE-71 exposure. Analysis of F1 eggs indicated that parental exposure to DE-71 could result in a transfer of PBDEs and thyroid hormones (THs) to their offspring. For the first time, we demonstrated that parental exposure to low concentrations of PBDEs could affect THs in the offspring and the transgenerational PBDE-induced toxicity in subsequent nonexposed generations.

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Perfluorooctane sulfonate (PFOS) is widely distributed and persistent in the environment and in wildlife, and it has the potential for developmental toxicity. However, the molecular mechanisms that lead to these toxic effects are not well known. In the present study, proteomic analysis has been performed to investigate the proteins that are differentially expressed in zebrafish embryos exposed to 0.5 mg/l PFOS until 192 h postfertilization. Two-dimensional electrophoresis coupled with mass spectrometry was employed to detect and identify the protein profiles. The analysis revealed that 69 proteins showed altered expression in the treatment group compared to the control group with either increase or decrease in expression levels (more than twofold difference). Of the 69 spots corresponding to the proteins with altered expression, 38 were selected and subjected to matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (TOF/TOF) analysis; 18 proteins were identified in this analysis. These proteins can be categorized into diverse functional classes such as detoxification, energy metabolism, lipid transport/steroid metabolic process, cell structure, signal transduction, and apoptosis. Overall, proteomic analysis using zebrafish embryos serves as an in vivo model in environmental risk assessment and provides insight into the molecular events in PFOS-induced developmental toxicity.

Despite suspended solids being an important water-quality parameter in the regulatory process, very little is known about the risks of prolonged exposure to high concentrations of suspended solids in fish, especially marine species. In this study, the green grouper Epinephelus coioides, an important mariculture species with a wide geographic distribution, was exposed to various concentrations (0, 50, 100, 200, 1000 and 2000 mg l -1 ) of suspended solids for 6 wk. The results showed that exposure was not lethal at environmentally realistic concentrations, and no changes in food intake, growth and RNA:DNA ratio were observed. However, damages to gill structure, including epithelium lifting, hyperplasia in the pillar system, and reduction of epithelial volume, were clearly evident, and strongly correlated with suspended solid concentration exposure. Despite the observation that serum osmolarity and haematocrit values did not change, Na + , K + -ATPase activities and chloride cells of the gill lamellae were altered, indicating that fish were experiencing osmoregulatory stress. Reduction in levels of free triiodothyronine (T3) in serum further confirmed that fish were experiencing physiological stress with suspended solids exposure. The overall results suggested that prolonged exposures can cause sub-lethal stress and compromise fish health, even though the high suspended solids we delivered were in concentrations that have been reported in coastal environments as not lethal to green grouper. KEY WORDS: Suspended solids · Grouper · Gill structure · Triiodothyronine · Osmoregulation · Growth · RNA:DNA ratio Resale or republication not permitted without written consent of the publisher

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