Tannery effluent-induced toxicity in giant amazon river turtle (Podocnemis expansa) juveniles: behavioral responses and erythrocyte nuclear abnormalities.

Abstract

Exposure to tannery effluents poses a significant threat to aquatic biodiversity, particularly in tropical ecosystems, where data on ecotoxicological impacts on aquatic reptiles remains scarce. This study investigated the effects of such exposure on juvenile Podocnemis expansa over a 21-day period, addressing a critical gap in understanding these impacts on chelonians. The effluent, collected from a "wet-blue" tannery and rich in heavy metals (Cr, Zn, Mg, Ca), was tested at three environmentally relevant dilutions: TE1.4 (1.4%), TE3.1 (3.1%), and TE6.5 (6.5%), along with negative (C) and positive (C+) control groups. Behavioral, physiological, and cyto-genotoxic biomarkers were evaluated. Although body mass was not significantly affected, reduced locomotor activity and increased latency to the first upward movement were observed, particularly in the TE3.1 and TE6.5 groups. In the righting response test, the TE6.5 group showed higher attempts and reduced righting efficiency, indicating neuromuscular impairments. Additionally, glycemic levels decreased by up to 11.3% in the TE3.1 and TE6.5 groups, while bioaccumulation of Cr, Zn, and Ca in the liver was significantly higher in the TE6.5 group. Social behavior alterations were also evident, with exposed individuals displaying selective responses and, in the TE6.5 group, behavioral inversion characterized by attraction to heterospecific stimuli. The significant increase in erythrocyte nuclear abnormalities indicated cytogenotoxic effects comparable to those of the C+ group. Multivariate analysis confirmed that the effects were most pronounced in the TE6.5 group, with complex interactions among the evaluated biomarkers. These findings highlight the environmental risks associated with tannery effluents and emphasize the need for mitigation strategies to protect tropical aquatic species, such as P. expansa, from ecotoxicological threats.