Sexual characteristics are altered by 4-tert-octylphenol and 17beta-estradiol in the adult male guppy (Poecilia reticulata).

Endocrine-disrupting chemicals (EDCs) are believed to interfere with animal reproduction, but only few biomarkers above the cellular level have been developed to assess the adverse effects of these chemicals. Using the guppy (Poecilia reticulata) as a model organism, studies have been undertaken with the object of comparing biomarker responses to EDCs at increasing levels of biological complexity. Short-term exposure to the xenoestrogen 4-tert-octylphenol and the natural estrogen 17beta-estradiol (E2) changed important sexual characteristics in the adult male guppy. Both compounds increased the number of sperm cells in the ejaculates, reduced the area and color intensity of the sexually attractive orange spots, and inhibited testis growth. In the case of E2, the effects on sperm count and coloration were still evident after 3 months of recovery in clean water. Preliminary results on male reproductive capability demonstrated that treated males produced fewer offspring than untreated fish, indicating an impairment of reproduction itself.