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Abstract

Litopenaeus vannamei postlarvae were exposed during 4 weeks to progressively increasing sublethal concentrations of cadmium and zinc (Cd: 8.8, 24, Zn: 81, 160, ), used alone or in mixture, in order to evaluate their joint effect on survival and growth, and on the histological structure of hepatopancreas and gills of the exposed organisms. After exposure to single metals there were no differences between control and treatments in survival and growth, while survival was significantly lower with the highest concentration of the mixture. Growth was also affected and showed a significant dose-related response. No histopathologies were observed in gills of shrimps exposed to single metals, while their hepatopancreas showed moderate to severe changes during the first three weeks. With the mixture, moderate edemas were present in gills lacunae and the hepatopancreas had sloughing of epithelial cells until the third week, but no histological alterations were evident by the end of the experiment. The results of this study show a synergistic effect of the mixture Cd + Zn on survival, growth and histological structure of hepatopancreas and gills of the Pacific white shrimp L. vannamei.