RESUMEN
Arsenic (As) contamination in aquatic environment adversely impacts aquatic organisms. The present study assessed the toxicity of different As species and concentrations on bighead carp (Hypophthalmichthys nobilis) at early life stage, a major fish in Yangtze River, China. We measured the changes in embryo and larvae survival rate, larvae aberration, concentrations of thyroid hormone thyroxine, and transcription levels of thyroid hormone receptors (TRs) in fish larvae after exposing to arsenite (AsIII) or arsenate (AsV) at 0, 10, 30, 50, 100, or 150 µg L(-1) for 78 h. As concentrations ≤ 150 µg L(-1) had limited effect on embryo survival rate (6-8% inhibition), but larvae survival rate decreased to 53-57% and larvae aberration rate increased to 20-24% after As exposure. Moreover, thyroxine levels elevated by 23% and 50% at 100 µg L(-1) AsIII and 150 µg L(-1) AsV. Besides, AsIII and AsV decreased the transcriptional levels of TRα by 72 and 53%, and TRß by 91 and 81% at 150 µg L(-1) As. Our data showed that AsIII and AsV had limited effect on carp embryo survival, but they were both toxic to carp larvae, with AsIII showing more effect than AsV. As concentrations <150µg L(-1) adversely influenced the development of bighead carp larvae and disturbed their thyroid hormone homeostasis.