Determining the effects of the polycyclic aromatic hydrocarbon phenanthrene on the reproductive axis in the fathead minnow (Pimephales promelas)

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University of New Brunswick


Phenanthrene is a polycyclic aromatic hydrocarbon and environmental contaminant. Phenanthrene is found naturally in oil, coal and tar deposits and can enter the environment through volcanic eruptions and is formed through incomplete combustion of organic material. This can occur naturally, e.g. forest fires, or through anthropogenic activities and accidents such as oil spills. Therefore, phenanthrene can enter the aquatic environment and can negatively affect fish health (e.g. impair immune system function and stimulate oxidative stress). Phenanthrene can have negative impacts on different biological systems including the reproductive axis, but data are lacking on how this occurs. To improve our mechanistic understanding of this PAH, fathead minnows (FHM; Pimephales promelas) were exposed to phenanthrene in acute (72 hrs) and sub-chronic (7 weeks) experiments and responses assessed in the liver and hypothalamus (7 weeks only) using transcriptomics, in addition to reproductive and behavioural (7 weeks only) endpoints (steroid production, oocyte distribution, swimming speed). Phenanthrene altered cortical alveolar oocyte proportions after acute exposure, however this was not associated with a change in 17β-estradiol production. Transcriptomic analyses in hepatic tissues suggested phenanthrene altered energy homeostasis after acute exposure. After sub-chronic exposure, phenanthrene altered swimming behaviour (increasing burst speeds, male only), condition factor, gonadosomatic index (females only) and gamete stage proportions in male and female FHM. Transcriptomic analyses of hepatic tissues suggested altered energy homeostasis while analyses in the hypothalamus suggested sex-specific responses to phenanthrene. This is the first study to characterize the effects of phenanthrene exposure in fish using an integrated systems biology approach on a temporal scale. These data improve understanding as to how this PAH affects molecular and biological responses in aquatic organisms.