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Action of two endocrine disrupters on the sexual differenciation of Nile tilapia Translated title: Ação de dois desreguladores endócrinos na diferenciação sexual da tilápia do Nilo

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      Abstract

      ABSTRACT Endocrine disruptors are exogenous substances that can impair one or more functions of the endocrine system and cause adverse effects to the health of an intact organism. The main goal of this study was to evaluate the effect of the endocrine disruptors 17β-estradiol (E2) and 17α-ethinyl estradiol (EE2) on the sexual differentiation of Nile tilapia during spawning. Six treatments and one control with three replications, totalizing 21 experimental units, were assessed in a completely randomized design. Hormones were dosed at concentrations of 250, 500, and 1,000 ng L−1 (treatments E2-250, E2-500, E2-1,000, EE2-250, EE2-500, and EE2-1,000). Exposure to hormones occurred during the first 28 days of life. After this period, water was completely renewed and individuals kept in their respective experimental units for another 60 days, totaling 88 days. At the end of this period, animals were euthanized by ice desensitization for gonad extraction, slide preparation, and observation under an optical microscope. At the end of the experiment, the results indicated that the type of hormone and hormone concentration differentially affected the parameters of zootechnical performance. A significant difference (p<0.05) was observed in the condition factor between control and treatments. Intersex individuals were observed in treatments of both hormones, except for the control treatment. In addition, malformations were observed in individuals submitted to treatments, mainly in the head region. Thus, the presence of the chemical compounds 17β-estradiol and 17α-ethinylestradiol severely affected the development and sexual differentiation of Nile tilapia.

      Translated abstract

      RESUMO Desreguladores endócrinos são substâncias exógenas que possuem a capacidade de alterar uma ou várias funções do sistema endócrino com efeitos adversos a saúde um organismo intacto. O objetivo principal do presente trabalho foi avaliar a ação dos desreguladores endócrinos 17β-estradiol (E2) e 17α-etinilestradiol (EE2) na diferenciação sexual da tilápia do Nilo durante o período de alevinagem. Foram avaliados seis tratamentos e um controle, com três repetições, totalizando 21 unidades experimentais em um delineamento inteiramente casualizado. Os hormônios foram dosados nas concentrações de 250; 500 e 1.000 ng L-1 (E2-250; E2-500; E2-1.000; EE2-250; EE2-500; EE2-1.000). A exposição aos hormônios ocorreu durante os primeiros 28 dias de vida. Após este período a água foi totalmente renovada e os indivíduos mantidos em suas respectivas unidades experimentais por mais 60 dias, totalizando 88 dias. Ao final deste período os animais foram eutanasiados por insensibilização em gelo para extração das gônadas, preparação das lâminas e observação sob microscópio óptico. Ao final do experimento foi possível constatar que os hormônios e as concentrações hormonais avaliadas afetaram distintamente os parâmetros de desempenho zootécnico. Foi observada diferença significativa (p<0,05) no fator de condição entre o controle e os tratamentos. Indivíduos intersexo foram observados nos tratamentos de ambos os hormônios, com exceção do controle. Além disto, foram observadas malformações nos indivíduos dos tratamentos, principalmente na região da cabeça. Com os dados coletados na presente pesquisa é possível concluir que a presença dos compostos químicos 17β-estradiol e 17α-etinilestradiol afetam severamente o desenvolvimento e a diferenciação sexual da tilápia do Nilo.

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      Most cited references 25

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      The Length-Weight Relationship and Seasonal Cycle in Gonad Weight and Condition in the Perch (Perca fluviatilis)

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        Sex determination and sex differentiation in fish: an overview of genetic, physiological, and environmental influences

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          Intersex and reproductive impairment of wild fish exposed to multiple municipal wastewater discharges.

          The Grand River watershed in Ontario, Canada, receives and assimilates the outflow of 29 Municipal Wastewater Effluent (MWWE) discharges which is a mixture of domestic and industrial wastes. The purpose of this study was to investigate the cumulative impact of multiple sewage discharges on populations of wild fish. In field studies, responses of fish populations and individual fish responses in terms of growth (condition factor), reproduction (in vitro sex steroid production, gonadosomatic indices, histology [cellular development and intersex]) were assessed upstream and downstream of two municipal discharges. Fish [Greenside Darters Etheostoma blennioides and Rainbow Darters E. caeruleum] collected downstream of two municipal wastewater plants had the potential to have greater growth (longer and heavier) when compared to reference fish collections regardless of sex. Fish were not assimilating additional anthropogenic resources into energy storage (increased condition, liver somatic index). Impacts on ovarian development appeared to be minor with no differences in growth, steroid production or cellular development. Sewage exposed male fish were experiencing impairment in the capacity to produce testosterone and 11-ketotestosterone in vitro, and in cellular development (GSI, intersex). Male darters of both species collected in the upstream agricultural region demonstrated no evidence of intersex whereas our urban reference sites had incidence of intersex of up to 20%. Rates of intersex were elevated downstream of both sewage discharges studied (33% and>60%, respectively). Lower rates of intersex at the intermediate sites, and then increases downstream of second sewage discharge suggests that fish populations have to potential to recover prior to exposure to the second sewage effluent. Pre-spawning darters demonstrated dramatically higher incidence of intersex in the spring at both urban reference sites (33% and 50%, respectively), and increased more so downstream of the near-field and far-field exposure sites (60% and 100%, respectively). These findings suggest that the compounds released in STP effluents have a tendency to act on the male reproductive system. These effects may become more pronounced as projected human population growth will require the aquatic environment to assimilate an increasing amount of sewage waste. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.
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            Author and article information

            Affiliations
            Fortaleza Ceará orgnameUniversidade Federal do Ceará orgdiv1Centro de Tecnologia orgdiv2Departamento de Engenharia Hidráulica e Ambiental Brazil andre23@ 123456ufc.br
            Fortaleza Ceará orgnameUniversidade Federal do Ceará orgdiv1Centro de Ciências orgdiv2Departamento de Biologia Brazil jrobertofeitosa@ 123456gmail.com
            Fortaleza Ceará orgnameUniversidade Federal do Ceará orgdiv1Centro de Ciências Agrárias orgdiv2Departamento de Engenharia de Pesca Brazil passosneto.op@ 123456ufc.br
            Contributors
            Role: ND
            Role: ND
            Role: ND
            Role: ND
            Journal
            rca
            Revista Ciência Agronômica
            Rev. Ciênc. Agron.
            Universidade Federal do Ceará (Fortaleza, CE, Brazil )
            0045-6888
            1806-6690
            September 2019
            : 50
            : 3
            : 402-410
            S1806-66902019000300402
            10.5935/1806-6690.20190048

            This work is licensed under a Creative Commons Attribution 4.0 International License.

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            Figures: 0, Tables: 0, Equations: 0, References: 29, Pages: 9
            Product
            Product Information: SciELO Brazil
            Categories
            Fish Engineering

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