Análise comparativa da inocuidade viral de Artemia sp. alimentada com diferentes espécies de microalgas

Abstract

The health of shrimp farming is a limiting factor for the success of production, the presence of viral pathogens in Peneu vannamei crops affects the performance of shrimp farming in Brazil and in the world. Therefore, factors exogenous to the crop are routinely evaluated as means of contamination, especially in larvicultures, among possible vectors of diseases are the live food offered. Due to its good nutritional condition and ideal size, the microcrustacean of the genus Artemia is a potential food in shrimp diets, in addition to being easy to manage and cultivate. In addition, microalgae are commonly added as a food source. Therefore, the present study aimed to evaluate the viral harmlessness of Artemia sp., fed with the microalgae species Nannochloropsis oculata, Chaetoceros mueleri, Tetraselmis gracilis and Thalassiosira sp., in order to ensure that these live foods can be offered under proper sanitary conditions. The strains of the microalgae species were cultivated in 20 L carboys, in F/2 Guillard culture medium, salinity 20 ppm, for 15 days in constant aeration and lighting. For the cultivation of Artemias, five treatments with three replications each were arranged in 5 L reactors with seawater. The outbreak of the cysts was based on the methodology used by Takata (2007). Nauplii and metanauplii were counted in a Sedgewick Rafter chamber. The reactors were fed according to algal density, and the counts were performed under an optical microscope and a Neubauer camera. Total DNA was extracted with the DNAzole reagent. DNA quantification was performed in a spectrophotometer. Total RNA was extracted with the Trizol reagent. For viral analysis, White Spot Syndrome Virus (WSSV), Infectious Myonecrosis Virus (NVMI) and Hyperdermal Infection and Hematopoietic Necrosis Virus (IHHNV) were investigated. The qPCR reactions were performed containing the specific reagents for each pathogen. The qPCR reactions were performed containing the specific reagents for each pathogen. To quantify the copy number of WSSV and IMNV, the 7500 Real-time PCR system (Applied Biosystems®) platform was used. All samples were tested in duplicate and were only considered positive when there was valid amplification of both replicates. For IHHNV, the amplified samples were submitted to Melting Temperature analysis in order to verify the specificity curve of the amplified generated. The study showed that there was no viral detection in the samples, which demonstrates a satisfactory sanitary status for microcrustaceans and microalgae to be used as live food in the future, thus validating the procedure used in the present research.