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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03575

    Toxic effects in Aphanomyces brasiliensis and zebrafish embryos caused by oomyceticide

    Karen de Souza Ferreira*,Leonardo Tachibana, Débora Rodrigues da Silva Colombo, Sarah Cristina Oliveira da Paixão, Cláudia Maris Ferreira, Cíntia Badaró-Pedroso*

    *Corresponding author:

    ABSTRACT: In fish farming about 10% of losses occur during egg incubation and larviculture due to diseases caused by oomycetes. This study aimed to identify the oomycete species that occurs in Danio rerio (zebrafish) eggs and evaluate the oomyceticidal effect of copper sulfate, bronopol and methylene blue on the mycelial growth of this organism, as well as to determine the lethal and sublethal toxicity of these compounds in embryos of D. rerio. The isolates were cultivated in yeast-starch medium to determine the concentration necessary to inhibit mycelial growth by 50% (IC50) and 100% (minimum oomyceticidal concentration – MOC) after 96 hours exposure to these compounds. In addition, tests with D. rerio eggs were conducted to determine the lethal concentrations for 50% of the organisms (96h-LC50), and the concentrations that inhibited 17% of the egg hatching (96h-IC17) after 96h. The organism responsible for the mortality of D. rerio eggs was classified by classical and molecular methods as Aphanomyces brasiliensis, representing the first report of this pathogen in zebrafish eggs. IC50 values could be determined for both bronopol and copper sulfate, whereas methylene blue had low effectiveness against the oomycete. However, copper showed high toxicity to D. rerio eggs in low concentrations, while methylene blue and bronopol toxicity was low and similar to each other. The use of the concentrations suggested in this study for the treatment of eggs of this species allows to control the pathology without causing effects to the treated organisms.