Translucent disease outbreak in Penaeus vannamei post-larva accompanies the imbalance of pond water and shrimp gut microbiota homeostasis

Abstract

The health status of aquatic animals is closely related to environmental and gut microbiota. Imbalance in microbiota homeostasis may be an important cause of diseases outbreak in aquaculture. A new disease called "translucent post-larva disease" (TPD) or "bacterial vitrified syndrome" (BVS) has caused huge economic losses to Penaeus vannamei seed industry of China in recent years. However, no studies have been reported on the relationship between this disease and microbiota homeostasis in gut or environment. In the present study, we obtained a batch of shrimp post-larva (PL) showing translucent diseased features in clinically and histologically. We used high-throughput sequencing to analyze the differences of microbiota between healthy and diseased shrimp PL, and corresponding pond water. The results of alpha diversity analysis showed, the Shannon and Smithwilson indexes in diseased shrimp PL gut were significantly higher (P < 0.05). In addition, the occurrence of the disease increased similarity of microbiota characteristics between shrimp PL gut and pond water. Specifically, the microbiota clustering distance was shortened, and shared OUTs were increased between diseased shrimp PL gut and water. The abundance of Ralstonia in diseased shrimp PL gut was significantly decreased (P < 0.05), while Vibrio and Mycoplasmataceae were largely enrichment. The abundance of Vibrio in diseased shrimp PL gut reached to 50.04 %, and the dominant strain was identified as being the closest to V. owensii and V. hyugaensis. Functional prediction results showed that the abundances of genes closely related to bacterial growth, colonization, secretion and transport of virulence factors, such as carbohydrate metabolism, two-component system and membrane transport, were significantly increased in diseased shrimp PL gut (P < 0.05). This study provides a theoretical basis for a relationship between the occurrence of shrimp PL translucent disease and the imbalance of microbial homeostasis, and provides guidance for the disease prevention during shrimp farming.