Fathead Minnow Response to Broad-Range Exposure of Beta-Sitosterol Concentrations During Life-Cycle Testing

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Coastal Sciences, Gulf Coast Research Laboratory


The -sitosterol concentration in pulp and paper mill effluents is typically greater than that of other phytosterols and has been shown to cause a variety of effects in fish. The authors exposed fathead minnow (Pimephales promelas) to low (22 +/- 0.93 mu g/L), medium-low (70 +/- 2.1 mu g/L), medium-high (237 +/- 5.5 mu g/L), and high (745 +/- 16.2 mu g/L) concentrations of -sitosterol as well as negative (water), positive (ethynyl estradiol, 16 +/- 0.58ng/L), and carrier (0.6mL/L acetone) controls. Fish were monitored over a full life cycle for population-level endpoints including growth and survival, reproductive endpoints (e.g. fecundity, sex steroids and vitellogenin, gonado-/hepatosomatic indices, and gonad histology). No significant differences were seen in fish growth, mortality, or reproduction with -sitosterol exposure, although a trend for lower egg production in -sitosterol exposures relative to the water control may be related to the acetone carrier. All ethynyl estradiol-exposed fish were smaller, showed female characteristics, and did not spawn. Sex steroid and vitellogenin were highly variable with no detectable treatment-related differences. Gonadal tissue showed no -sitosterol-related differences in reproductive development and spawning capability, although most ethynyl estradiol-exposed males had ovarian tissue and were not spawning-capable. The results indicate that -sitosterol exposure had little apparent impact on fathead minnow survival, growth, and reproduction even at concentrations >10 times that of typical effluents, although small sample size and variability precluded fully evaluating treatment responses on sex steroids and vitellogenin. (c) 2013 SETAC

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Environmental Toxicology and Chemistry





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