John Wiley & Sons, Ltd.

Fathead Minnow response to broad‐range exposure of β‐sitosterol concentrations during life cycle testing

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β‐sitosterol concentration in pulp and paper mill effluents is typically greater than other phytosterols, and has been shown to cause a variety of effects in fish. We exposed Fathead Minnow (Pimephales promelas) to low (22 ± 0.93 µg/L), medium‐low (70 ± 2.1µg/L), medium‐high (237 ± 5.5 µg/L), and high (745 ± 16.2 µg/L) concentrations of β‐sitosterol; and a negative (water), positive (ethynyl estradiol, EE2, 16 ± 0.58 ng/L), and carrier control (0.6 ml/L acetone). 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 index, and gonad histology). No significant differences were seen in fish growth, mortality, or reproduction with β‐sitosterol exposure, although a trend for lower egg production in β‐sitosterol exposures relative to the water control may be related to the acetone carrier. All EE2‐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 β‐sitosterol‐related differences in reproductive development and spawning capability, although most EE2‐exposed males had ovarian tissue and were not spawning capable. Results indicate that β‐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. Environ Toxicol Chem © 2013 SETAC

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