Delayed impacts of developmental exposure to 17-α-ethinylestradiol in the self-fertilizing fish Kryptolebias marmoratus

- As a selfing hermaphrodite, mangrove rivulus allows to work with isogenic lineages.
- Growth reduction after 28-day EE2 is followed by compensatory growth in clean water.
- Mangrove rivulus is able to maintain reproduction at high EE2 concentrations.
- Early-life EE2 exposure triggers a delayed increase in adults' androgens.

17-α-ethinylestradiol (EE2) is one of the most potent endocrine disrupting compounds found in the aquatic environments, and is known to strongly alter fish reproduction and fitness. While the effects of direct exposure to EE2 are well studied in adults, there is an increasing need to assess the impacts of exposure during early life stages. Sensitivity to pollutants during this critical window can potentially affect the phenotype later in life or in subsequent generations. This study investigated phenotypic outcome of early-life exposure to 17-α-ethinylestradiol during development and in adults of the mangrove rivulus, Kryptolebias marmoratus. Being one of the only two known self-fertilizing hermaphroditic vertebrates, this fish makes it possible to work with genetically identical individuals. Therefore, using rivulus makes it possible to examine, explicitly, the phenotypic effects of environmental variance while eliminating the effects of genetic variance. Genetically identical rivulus were exposed for the first 28 days post hatching (dph) to 0, 4 or 120 ng/L of EE2, and then were reared in uncontaminated water until 168 dph. Growth, egg laying and steroid hormone levels (estradiol, cortisol, 11-ketotestosterone, testosterone) were measured throughout development. Exposed fish showed a reduction in standard length directly after exposure (28 dph), which was more pronounced in the 120 ng/L group. This was followed by compensatory growth when reared in clean water: all fish recovered a similar size as controls by 91 dph. There was no difference in the age at maturity and the proportions of mature, non-mature and male individuals at 168 dph. At 4 ng/L, fish layed significantly fewer eggs than controls, while, surprisingly, reproduction was not affected at 120 ng/L. Despite a decrease in fecundity at 4 ng/L, there were no changes in hormones levels at the lower concentration. In addition, there were no significant differences among treatments immediately after exposure. However, 120 ng/L exposed fish exhibited significantly higher levels of testosterone at 91 and 168 dph and 11-ketotestosterone at 168  dph, up to 140 days after exposure. These results indicate that early-life exposure to EE2 had both immediate and delayed impacts on the adult's phenotype. While fish growth was impaired during exposure, compensatory growth, reduced fecundity and modification of the endocrine status were observed after exposure ceased.