ESTROGENIC CHEMICAL POLLUTANTS AFFECT GROWTH AND REPRODUCTION-RELATED GENES IN MALE MOZAMBIQUE TILAPIA Oreochromis mossambicus

Accumulation of waste products and chemical pollution  in aquatic environments is detrimental to humans and aquatic life. Many of these pollutants, termed endocrine disrupting chemicals (EDCs), often affect the endocrine system of organisms that become exposed. EDCs  released into the environment through anthropogenic activities can have short-term and/or long-term  sustained  developmental  and physiological  effects on fish . While tilapia species have been widely studied with respect to how environmental conditions impact growth and reproduction , little is known on how  tilapia and other tropical fish species  respond to EDC exposure.  Our present study aims to determine the long-term physiological effects of early-life exposure  of tilapia fry  to nonylphenol (NP), an environmentally pervasive byproduct of plastic production that mimics the actions of estrogens.

We exposed  Mozambique tilapia fry to waterborne NP (10 and 100 µg/L) for 21 days . 17β-estradiol  (E2; 0.1 and 1.0 µg/L) was used as a control.  After the exposure period, juveniles were reared for an additional 112 days  without chemicals  until males were sampled. We found that hepatosomatic index was decreased by exposure to NP (100 µg/L), indicating an adverse effect on liver metabolism. Gonadosomatic index was elevated in fish exposed to E2 (0.1 µg/L) . E2 and NP stimulated hepatic estrogen receptor (erα and erβ) mRNA expression  but did not affect the expression of vtg transcripts (Figure 1). Furthermore,  the somatotropic axis of adult tilapia was impacted by early-life exposure to NP and E2. Hepatic mRNA levels of growth hormone receptor (ghr ), insulin-like growth factor 1 (igf1) ,  and igf-binding proteins (igfbps )  were  affected  by exposure to E2 and NP.  We conclude that tilapia exposed to E2 and NP as yolk-sac fry exhibit subsequent changes in the endocrine systems that control growth and reproduction during their adult life.

[Supported by HATCH (#HAW02051-H), NOAA/ UH-Sea Grant  (#NA14OAR4170071, R/SB-18),  NOAA (#NA18OAR4170347), NIH (1R21DK111775-01) and NSF (IOS-1755016 and -1755131)]