Effect of atrazine on the sex ratio of the Neotropical fish, Odontesthes bonariensis, exposed during the thermolabile window of sex determination.

CARRIQUIRIBORDE, P.; LÓPEZ, G. C.; TRUDEAU, V. L.; SOMOZA, G M.

Minneapolis

Congreso; SETAC North America 38th Annual Meeting; 2017

SETAC

Atrazine is an herbicide heavily used worldwide. Due to its physicochemical properties andenvironmental behavior, it is frequently found in the aquatic ecosystems. In addition, a lot ofevidence exist on the adverse effects of atrazine on aquatic vertebrates, particularly acting as anendocrine disrupting compound (EDCs), modulating aromatase activity. The inland ?Pejerrey? (O.bonariensis), is characteristic fish of the southern sector of the Río de la Plata Basin. In addition,Pejerrey presents thermolabile‐sex determination (TSD) that happens between the 2nd and 6thweek after hatching and therefore it could be particularly sensitive to EDCs. All females or males areexpected at 19 °C or 28 °C, respectively, while 50% female and male are expected at 25 °C. In thepresent study we evaluate for the first time, the effects of atrazine on the sex determination ofPejerrey during the thermolabile window. Twenty‐five fish were exposed in 60L stainless steel tanksto 0, 0,5, 5 and 50 μg/L of atrazine (a.i.) from the 2nd to 6th week after hatching, by duplicated. Inaddition, a group was exposed to 0,025 μg/L of EE2 as positive control. Ten fish per treatment weresampled at week 6 for molecular biology and 15 fish were later sampled at week 12 for histology.Gonadal histology showed that in the control group, 60% were males and 40% females while in thepositive control 100% of fish were females. In fish exposed to the highest concentration of atrazine,73% females, 18% undetermined and 9% males were obtained. This first obtained results suggestthat the herbicide was able to skew the sex ratio, feminizing Pejerrey during the thermolabilewindow.