Reproductive effects of oestrogenic endocrine disrupting chemicals in Astyanax rivularis inhabiting headwaters of the Velhas River, Brazil

The Velhas River is the most polluted river in the state of Minas Gerais, south-eastern Brazil. Due to its historical and environmental relevance, the aim of this study was to evaluate the effects of oestrogenic endocrine disruptors on the reproduction of the lambari Astyanax rivularis, a small-sized species found in headwaters of the São Francisco River basin. Quarterly field samplings were carried out during a reproductive cycle in three streams of the upper Velhas River: S1 (reference site) and S2 and S3 (sites contaminated by untreated sewage). The main oestrogenic compounds were evaluated in water using HPLC/MS. Molecular, histological and reproductive biomarkers were assessed in liver and gonad. The results showed higher average concentrations of oestradiol (> 200 ng/l) in S2 and S3, oestrone (> 250 ng/l) in S2 as well as oestriol (> 200 ng/l), bisphenol A (> 190 ng/l), and nonylphenol (> 600 ng/l) in S3 compared to S1 (< 70 ng/l for all compounds). In S2 and S3, there was an increase in the proportion of females, higher ELISA levels of vitellogenin (Vtg) and proteins of the zona radiata (Zrp) in liver males. Insulin-like growth factor (IGF-I) levels were lower in S2 males, which also had a smaller body size, a smaller seminiferous tubule diameter, a higher proportion of spermatogonia, and lower proportion of spermatozoa in relation to S1. Histopathological analyses detected an increase in yolk deficient oocytes and over-ripening in the contaminated sites, and these alterations were associated to a reduction of hepatic Vtg levels and a delay in spawning, respectively. Intersex specimens with perinucleolar follicles in a multifocal distribution in the testis were detected in S2 and S3. These results indicate that chronic exposure to oestrogenic compounds induced endocrine disruption that may affect wild populations of A. rivularis in the Velhas River. - Highlights: • Oestrogenic EDCs were assessed by HPLC/MS in Velhas River headwaters, Brazil. • Over-ripening and yolk deficient oocytes can be novel biomarkers of oestrogenic EDCs. • Intersex gonads showed perinucleolar follicles into the seminiferous tubules. • ELISA assays showed higher hepatic Vtg levels in males from impacted sites. • Physiological follicular atresia occurred in sites contaminated by oestrogens.