Cadmium exposures in fathead minnows: are there sex-specific differences in mortality, reproductive success, and Cd accumulation?

The primary goal of this experiment was to determine whether cadmium (Cd) exposure has sex-specific effects on the reproductive success of fathead minnows as measured by time to first spawn, spawning frequency, clutch size, fecundity, fertilization success, hatching success, and offspring mortality to 2 d post hatch. Prior to breeding, minnows were either exposed to 50 microg/L Cd or sham exposed for 21 d. After exposures, minnows were paired (male x female) into one of four breeding groups-control x control (C x C), control x exposed (C x E), exposed x control (E x C) or exposed x exposed (E x E). Pairs of minnows were subjected to a 21-d breeding study during which the reproductive parameters mentioned above were measured. During the breeding study, minnows in the E x E pairs had significantly higher mortality than minnows in the C x C pairs; however, the mortality of minnows in the C x E and E x C did not differ from that of C x C pairs. Presumably, behavioral alterations in both males and females exposed to Cd accounted for the increased mortality in the E x E group. The results of the breeding study did not reveal any significant differences among any of the reproductive parameters measured with the exception of offspring mortality. Offspring from C x E pairs did not differ from offspring from C x C pairs with regard to mortality; however, offspring from pairs containing exposed males (E x C and E x E) had significantly higher mortality than offspring from C x C pairs suggesting that paternal exposure to Cd leads to an increase in offspring mortality.