Histopathological alterations in gills of a fish (Astyanax bifasciatus) in neotropical streams: negative effects of riparian forest reduction and presence of pesticides Jardel Nimet & Mayara Pereira Neves & Natália Prudêncio Viana & João Paulo de Arruda Amorim & Rosilene Luciana Delariva Received: 30 September 2019 /Accepted: 9 December 2019 # Springer Nature Switzerland AG 2019 Abstract The reduction of riparian vegetation around aquatic environments causes several physico- chemical alterations and favors the entry of pesticides via surface runoff. Such changes have negative ef- fects on aquatic organisms. In this study, we evaluat- ed histopathological alterations in gills of Astyanax bifasciatus to test the hypothesis that more severe histopathological alterations occur in gills of fish from streams with higher agricultural impact from the surrounding area. The specimens were collected by electrofishing in seven streams of the lower Iguaçu basin between August 2015 and February 2016. The gills were processed according to routine histological methods and examined by light micros- copy. The histopathological alterations, mainly stage II (lamellar aneurysm and total fusion of lamellae), were observed in fish collected in streams with higher agricultural activity. In these streams, the his- topathological index indicated slight to moderate or- gan lesions. In contrast, in streams with more vege- tation cover, fish collected presented stage I histo- pathological alterations (lamellar edema and lamellar hyperplasia), and the HI indicated normal function- ing of the gills. In addition, chloride and acid mucous cells were more abundant in the gills of fish collected in rural streams. Our findings demonstrate that more severe histopathological alterations were registered in fish collected from streams with intense agricul- tural activity in the surrounding area. Therefore, it highlights that vegetation cover around the streams is a positive force for the conservation and health of aquatic organisms. Environ Monit Assess (2020) 192:58 https://doi.org/10.1007/s10661-019-8030-y J. Nimet (*) Universidade Estadual de Maringá, Centro de Ciências Biológicas, Programa de Pós-Graduação em Biologia Comparada, Avenida Colombo 5790, bloco G-80, sala 201. CEP 878020-900., Maringá, Paraná (PR), Brazil e-mail: jardelnimet@gmail.com M. P. Neves Departamento de Zoologia, Pós-graduação em Biologia Animal, Universidade Federal do Rio Grande do Sul, Instituto de Biociências, Avenida Bento Gonçalves 9500, bloco IV, prédio 4343-5. CEP 91501-970, Porto Alegre, Rio Grande do Sul (RS), Brazil e-mail: mayara-nevesbio@hotmail.com N. P. Viana Universidade Federal de São Carlos, Pós-graduação em Ecologia e Recursos Naturais. Rodovia Washington Luiz km 235, Caixa postal 676. CEP 13565-905, São Carlos, São Paulo (SP), Brazil e-mail: natpviana@hotmail.com J. P. de Arruda Amorim Centro de Ciências Biológicas e Saúde, Laboratório de Biologia Tecidual e Reprodução, Universidade Estadual do Oeste do Paraná. Rua Universitária 2069, Caixa postal 711. CEP 85819-110, Cascavel, Paraná (PR), Brazil e-mail: joao.amorim@unioeste.br R. L. Delariva Universidade Estadual do Oeste do Paraná, Centro de Ciências Biológicas e da Saúde. Programa de Pós-Graduação em Conservação e Manejo de Recursos Naturais. Rua Universitária 2069, Caixa postal 711. CEP 85819-110, (+55 045)3220-7396, Cascavel, Paraná (PR), Brazil e-mail: rosilene.delariva@hotmail.com