Insights about the toxic effects of tannery effluent on Lithobates catesbeianus tadpoles

Highlights: • Tadpole exposed to untreated tannery effluent (UTE) presented morphologic changes. • Exposure of L. catesbeianus tadpoles to UTE caused cytotoxic effects. • The total of other nuclear abnormalities was influenced by UTE. • Tadpoles exposed to the UTE presented abnormal responses in the predator-response test. Tannery industries are considered highly polluting due to the large production of polluted wastewater [untreated tannery effluent (UTE)]. Although previous studies have already shown the consequences from fish, birds and mammals' exposure to this pollutant, little is known about its toxicological effect on representatives of class amphibian. Thus, we aim at assessing whether short-term UTE exposure, even at low concentrations (0.2% UTE diluted in water), would be able to induce behavioral, morphological and cyto-genotoxic changes in L. catesbeianus tadpoles. In order to do so, two experimental groups were set (control and tannery effluent) and exposed, or not, to UTE for seven days. A positive control group (cyclophosphamide) was included in the experimental design in order to assess cyto-genotoxicity. Our behavioral results showed that tadpoles exposed to the contaminant presented abnormal responses in the predator-response test; therefore, it evidenced losses in their capacity to recognize chemical olfactory cues of a potential predator. We also searched for changes in mouth length, in dentition, in body length before and after the eyes of animals exposed to UTE. Besides, we observed higher nuclear abnormality frequency in the circulating erythrocytes of tadpoles exposed to the contaminant, as well as in animals belonging to the positive control group. Some of the observed abnormalities were micronuclei, binucleated, notched, kidney-shaped and blebbed cells, multilobulated nuclei, as well as lower mitotic index. Therefore, our data confirm the hypothesis that UTE causes behavioral, morphological and cyto-genotoxic changes in L. catesbeianus tadpoles, fact that opens new perspectives to other investigations about how and which UTE constituents were responsible for the observed effects.