Effects of ethynylestradiol on morphology, gonadal histology and sex ratio at different life stages of Cnesterodon decemmaculatus (Pisces)

BRIAN YOUNG; JAVIER GASULLA; GABRIELA C. LÓPEZ; DIANA CRESPO; GUSTAVO M. SOMOZA; PEDRO CARRIQUIRIBORDE

Gainsville

Congreso; 5th Young Environmental Scientists Meeting.; 2016

SETAC

Teleost fish have a hormone-dependent sexual dimorphism and can be used as model organisms to study the adverse effects of estrogenic compounds. In this context, the aim of this study was to assess the long-term effects of 17α-ethynylestradiol (EE2) on secondary sexual characteristics, gonadal histology and sex ratio of Cnesterodon decemmaculatus males. Two experiments were conducted exposing fish to environmentally relevant concentrations of waterborne EE2 for three (in the case of fries) or four (adult males) months. Fish were exposed to 20, 100 and 200 ng/L of EE2 and a solvent control. In fries, concentration-dependent effects were observed on mortality, sex ratio and the occurrence of pigmentation in the perianal area. This pigmentation was observed in 0, 38, 85 and 100% of fish exposed to control, 20, 100 y 200 ng/L of EE2 respectively. The percentage of phenotypic males decreased from 49 (control) to < 17 % (20-200 ng/L) independently of the concentration. The highest percentage of females, 60%, was found at 100 ng/L. A concentration-dependent increase was observed in the number of sexually undifferentiated fish. Exposed adult males showed primary oocytes in the periphery of the testis since day 60 and 115 in fish exposed to 200 or 100 ng/L, respectively. Then primary oocytes were found in the central zone of the testis since day 85 in fish exposed to the highest dose. The histo-architecture of the ducts also showed several changes, such as the formation of ciliated cells in the epithelium and proliferation of parenchymal cells surrounding the spermatozeugmata. Histological changes were also observed in liver tissue, including steatosis and single cell necrosis at low concentrations or a generalized necrosis at the highest concentration. The gonopodium morphology did not show morphological alterations. Exposure of fry to EE2 alters sex ratio reducing male proportion. In sum this study shows that EE2 exposure effects vary according to the life stage at environmentally relevant concentrations and show that C. decemmaculatus can be used as a test organism to evaluate the impact of endocrine disruptors.