Cd exposures in fathead minnows: effects on adult spawning success and reproductive physiology.

The primary objective of this study was to determine whether cadmium (Cd) exposures alter reproduction in fathead minnows (Pimephales promelas). Pairs of sexually mature minnows were exposed to waterborne Cd at 0, 12.5, 25, or 50 microg/L for 21 days. During this exposure period, the reproductive success of pairs was assessed. Following the exposure, gonadosomatic index (GSI), male secondary sexual characteristics, male plasma 11-ketotestosterone (11-KT) concentrations, and female plasma estradiol (E2) concentrations were determined. Results of this study show that Cd exposures impair reproduction in fathead minnows. Pairs exposed to 50 microg/L experienced a significant decline in spawning frequency and fecundity relative to unexposed minnows. Cd exposures also caused alterations in male secondary sexual characteristics, as males exposed to 25 microg/L had significantly fewer nuptial tubercles than controls. Furthermore, males exposed to 12.5 microg/L Cd experienced a significant increase in plasma 11-KT concentrations relative to controls. No alterations in GSI or female plasma E2 concentrations were observed.