Systemic effects of nonylphenol on tadpoles of Lithobates catesbeianus: gonadal, genotoxic and color alterations

Endocrine disrupting chemicals (EDCs) are one of the most important factors contributing to worldwide amphibian decline since they alter hormonal regulation, affecting reproduction and development of organisms. One of the most used estrogenic compounds is the 4-nonylphenol (NP), which is a degradation product of lubricants, antioxidants, detergents, paints, and pesticides such as insecticides and herbicides. Here, we conducted an experiment to test the effects of NP on oogenesis, blood cell abnormalities, and body darkness of pre-metamorphic tadpoles of Lithobates catesbeianus. Tadpoles were exposed for 14 days to three concentrations of NP (1 µg/L, 10 µg/L, and 100 µg/L). Even though most animals were females, with ovarian-like cavity, oocytes or oogonia, intersex tadpoles were observed in control and treated groups. We found atretic oocytes in treated groups, characterized by nuclear picnosis, cytoplasmic retraction, and vacuolization. We found that NP increased body darkness and that it had genotoxic effects, increasing the number of nuclear abnormalities in erythrocytes. These results suggest that oogenesis can be disrupted or altered by exposure to NP, and that pigmentation can be used as a biomarker of exposure to this compound.<br>