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Figure: Continuous waterborne exposure to estrogen initiated during (A) early embryonic stage (eyed embryo) resulted in rapid hatching followed by mortality, while exposure from (B) the alevin stage resulted in high survival and molecular changes indicative of a role for estrogen in growth processes.

Estrogen exposure: Timing is everything

The motivation Estrogens in vertebrate animals are steroid hormones involved in reproductive processes (i.e. gonadal development, egg and egg yolk production).  However, estrogens also regulate additional physiological processes in non-reproductive tissues including growth, immune function, cardiovascular and skeletal systems, as well as the differentiation and regeneration of the central nervous system. The goal of this study was to examine the impacts of estrogen on growth and development at the molecular and whole organism level in early life stage salmonids.

The discovery – Simon Fraser University’s Vicki Marlatt is the lead author of a study that demonstrates that the timing of exposure to estrogen in rainbow trout during different developmental stages gives very different outcomes.  When estrogen exposure occurs during early embryonic stages prior to hatching, the animals hatch successfully and faster than control animals but die shortly thereafter.  However, when the same dose of estrogen is administered just after hatching while they are in the alevin developmental stage, the animals survive.  This study demonstrates how the timing of exposure to an estrogen is critical, with exposure prior to hatching resulting in adverse outcomes compared to exposure after hatching.   

Its significance –This research has implications for understanding the importance of estrogens in fish growth and development and for assessing the risk of environmental pollution.  Indeed, many pollutants found in the aquatic environment mimic or block the effects of estrogen in animals. Therefore, understanding the role of estrogen during development will aid in assessing the risk of these pollutants on developing salmonids, including rainbow trout. The next step for these researchers is to explore the effects of multiple doses of estrogens on fish development.

Read the paper“Molecular responses to 17β-estradiol in early life stage salmonids” by Marlatt VL, Sun J, Curran C, Bailey H, Kennedy CK, Elphick JR, Martyniuk CJ. Gen. Comp. Endocrinol. 203:203-214 (2014). DOI: 10.1016/j.ygcen.2014.03.023.

Website article compiled by Jacqueline Watson with Theresa Kitos