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

YOUNG, B.J.; GASULLA, J.; LÓPEZ, G.C.; CRESPO, D.; SOMOZA, G.M.; CARRIQUIRIBORDE, P.

Gainsville

Congreso; 5th Young Environmental Scientists Meeting.; 2016

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 EE  for three (in the case of fries) or four (adult males) months. Fish were exposed to 20, 100 and 200 ng/L of EE  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 EE  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  EE   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.