An environmental estrogen alters reproductive hierarchies, disrupting sexual selection in group-spawning fish.
There is global concern regarding the potential impacts of endocrine-disrupting chemicals (EDCs) on the health of wildlife and humans. Exposure to some estrogens, at concentrations found in the environment impairs reproductive function and behavior. However, nearly all work on endocrine disruption has investigated the effects of exposure on individuals and there is an urgent need to understand impacts on populations. Many fish have mating systems with complex social structures and it is not known whether EDCs will exaggerate or buffer the reproductive skews caused by the dominance hierarchies that normally occur for these species. This study investigated the impact of exposure to the pharmaceutical estrogen ethinylestradiol (EE2) on reproductive hierarchies and sexual selection in group-spawning fish. Breeding zebrafish were exposed to environmentally relevant concentrations of EE2, and effects were determined on reproductive output, plasma androgen concentrations (in males), and reproductive success through microsatellite analyses of the offspring. Reproductive hierarchies in breeding colonies of zebrafish were disrupted by exposure to EE2 at a concentration that did not affect the number of eggs produced. The effect was a reduction in the skew in male paternity and increased skew in female maternity. This disruption in the reproductive hierarchy in group spawning fish, if it occurs in the wild, has potentially major implications for population genetic diversity. Reproductive success in male zebrafish was associated with elevated plasma concentrations of the male sex hormone 11-ketotestosterone and this hormone was suppressed in EE2-exposed males.
Coe
Tobias S
TS
Ecotoxicology and Aquatic Biology Research Group, University of Exeter, Exeter, UK. tsc202@ex.ac.uk
Hamilton
Patrick B
PB
Hodgson
David
D
Paull
Gregory C
GC
Stevens
Jamie R
JR
Sumner
Katie
K
Tyler
Charles R
CR
D000728:Androgens / Q000097:blood; D000818:Animals; D017931:DNA Primers / Q000235:genetics; D004997:Ethinyl Estradiol / Q000633:toxicity*; D005260:Female; D006608:Hierarchy, Social; D008297:Male; D052586:Mating Preference, Animal / Q000187:drug effects*; D018895:Microsatellite Repeats / Q000235:genetics; D012098:Reproduction / Q000187:drug effects*; D013739:Testosterone / Q000031:analogs & derivatives / Q000097:blood; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015027:Zebrafish / Q000235:genetics / Q000502:physiology*
D000728:Androgens; D017931:DNA Primers; D014874:Water Pollutants, Chemical; D013739:Testosterone; D004997:Ethinyl Estradiol; C003600:11-ketotestosterone