The effects of chronic exposure to environmentally relevant levels of water-borne cadmium on reproduction in fathead minnows
Cadmium (Cd) is a priority pollutant in ecosystems worldwide. It is highly toxic to aquatic organisms including fish at fairly low concentrations. Numerous studies have investigated the influence of Cd exposure on fish, but few of them have considered how environmentally relevant levels of Cd affect reproduction, particularly reproductive behaviour. To assess the toxicity of Cd on fish reproduction, breeding fathead minnows (Pimephales promelas) were exposed to water-borne Cd for 21 days at four different concentrations (0, 1, 2.5 and 5 µg/L, respectively) based on a standard short-term reproductive assay and reproductive performance as well as behaviour were examined during or at the end of the exposure period. The results showed that Cd accumulated in a dose-dependent manner in the livers and ovaries of female fish. Brood size and mean egg production were significantly reduced in Cd-exposure treatment groups. When fertilized eggs were incubated in the water containing 2.5 µg/L or higher Cd, there was delayed hatching, but at the same time there was greater synchronous hatching after hatching started. Hatching success of Cd-exposed eggs also declined compared to the control. No significant difference was observed among treatments in adult fish survival, the number of breeding attempts, fertilization success, egg size, plasma β-estradiol levels of female, larval deformities, reproductive behaviour, gonadosomatic index or liver somatic index. The results of this study demonstrate that Cd is able to impair reproduction of fathead minnow at the concentration as low as 0.64 µg/L. It is harmful to both breeding fish and their offspring. The traditional endpoints used in standard reproduction assay (e.g. egg production and brood size) are probably more sensitive than behavioural endpoints, but the traditional method of interpreting reproductive impairment may underestimate toxic effects. The findings of this study have important implications for understanding the effects of chronic Cd exposure in metal-impacted feral fish populations. It can be applied to the protection or restoration of fish populations in Cd contaminated aquatic systems.
DegreeMaster of Science (M.Sc.)
SupervisorChivers, Douglas P.; Niyogi, Som
CommitteeWeber, Lynn P.; Pollock, Michael
Copyright DateOctober 2013
Environmentally realistic exposure