Masculinization in the Ten Spotted Live-Bearer Fish (Cnesterodon decemmaculatus) From the Middle Basin of the Reconquista River (Argentina) With High Anthropic Impact

CAMPOS LB; TRIPOLI LI; GENOVESE G; LO NOSTRO F; OSSANA NA

VIRTUAL

Congreso; Abstract Book SETAC Latin America 14th Biennial Meeting; 2021

SETAC

Fish are commonly exposed to several pollutants which can cause endocrine disruption. The Reconquista River (Buenos Aires) is the second most polluted river in Argentina, since it receives wastewater and untreated industrial discharges. Adults of Cnesterodon decemmaculatus (Poecillidae, Cyprinodontiformes), a viviparous freshwater fish, were collected from the middle river basin. Water samples were taken to analyze the physicochemical parameters. C. decemmaculatus possess external sexual dimorphism, where males are smaller than females and have an intromittent sexual organ (gonopodium). The aim of this work was to compare fish from the Reconquista river with a laboratory raised group (control) using biochemical, energetic metabolic, and histological biomarkers. Gonads were fixed using Bouin solution and stained with Masson's Trichrome for routine histological analysis. For biochemical and metabolic biomarkers analysis we dissected: brain for acetylcholinesterase activity (AChE); liver for glutathione-S-transferase activity (GST), catalase (CAT) and glutathione content (GSH); gills for GSH content; and muscle for AChE and energetic metabolism: lipids, carbohydrates, proteins and the electron transport system of the mitochondrial chain (ETS). Morphometric indices were also calculated: FC (condition factor), HSI and GSI (hepatosomatic and gonadosomatic index, respectively). Significant differences between groups were analyzed by “t” test or Mann Whitney for paired samples using Infostat software. When fish were sexed under a stereoscopic microscope, intersexes were found. These showed a relatively well developed gonopodium together with female gonads with vitellogenic follicles and embryos; no testicular tissue was found. Brain and liver biomarkers from the intersexes river fish showed a significant increase (+ 25/50%) of AChE and GST activities as well as of GSH content, in comparison with control group. Muscle ETS activity was lower from intersexes river fish (-200%). Furthermore, morphometric indices (FC and HIS), were higher in intersex fish than in control ones. Water quality showed a hypoxic condition and high ammonium levels. These results are the first evidence of masculinization in C. decemmaculatus females in an urban river under a several anthropic impact. Since this fish species is widely used as a sentinel in environmental monitoring studies, this features could be considered as an indicator of contamination by endocrine disruptors.