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(PM224) Secondary sexual characteristics are sensitive biomarkers for endocrine active chemicals.
Thorpe, K1, 2, Liney, K1, Tarr, J1, Benstead, R3, Hutchinson, T2, Tyler, C1, 1 University of Exeter, Exeter, Devon, UK2 Brixham Environmental Laboratory, Brixham, Devon, UK3 Environment Agency, Waterlooville, Hants, UK
ABSTRACT- Alterations in secondary sexual characteristics in various fish species have been demonstrated to be useful indicators of exposure to oestrogenic and androgenic chemicals. Male fathead minnows have two prominent androgen-dependent secondary sexual features; a dorsal fatpad and nuptial tubercles. Although normally only expressed in males, exposure of females to androgens has been shown to result in the induction of both the tubercles and fatpad. Pilot studies on control populations of fathead minnows found positive correlations between tubercle number, fatpad weight and testis weight, thus demonstrating that these characteristics are useful indicators of sexual maturation in males. A positive relationship was observed between body weight and fatpad weight in the males (P<0.05). To allow for differences in size between males a fatpad index (FPI) was derived, in which the fatpad weight is expressed as a percentage of body weight. Exposure of males to oestrone (32 to 1000 ng/L) resulted in concentration-dependent reductions in the FPI, (P<0.01), but no significant differences were observed between individual concentrations and controls (P>0.05). Exposure of males to an anti-androgen, linuron, (22 to 2200 ug/L) resulted in concentration-dependent reductions in both the FPI and tubercle numbers (P<0.01). The LOEC for the effect on the FPI was 220 ug/L (P<0.01). Work is currently ongoing to quantify the effects of these chemicals on the cellular components of the dorsal fatpad. These results demonstrate that the FPI is a sensitive biomarker for quantifying exposure to anti-androgens in male fathead minnows. Recent investigations have demonstrated a relationship between reductions in the FPI and a decreased fecundity in fathead minnows exposed to linuron, highlighting the importance of the FPI as a potential indicator of reproductive health.
Key words: fatpad, tubercles, oestrone, linuron
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