Abstract
When the aquaculture water environment deteriorates or the temperature rises, shrimp are susceptible to viral or bacterial infections, causing a large number of deaths. This study comprehensively evaluated the effects of the oral administration of a chitosan–gentamicin conjugate (CS-GT) after Litopenaeus vannamei were infected with Vibrio parahaemolyticus, through nonspecific immunity parameter detection, intestinal morphology observation, and the assessment of microbial flora diversification by 16S rRNA gene sequencing. The results showed that the oral administration of CS-GT significantly increased total hemocyte counts and reduced hemocyte apoptosis in shrimp (p < 0.05). The parameters (including superoxide dismutase, glutathione peroxidase, glutathione, lysozyme, acid phosphatase, alkaline phosphatase, and phenoloxidase) were significantly increased (p < 0.05). The integrity of the intestinal epithelial cells and basement membrane were enhanced, which correspondingly alleviated intestinal injury. In terms of the microbiome, the abundances of Vibrio (Gram-negative bacteria and food-borne pathogens) in the water and gut were significantly reduced. The canonical correspondence analysis (CCA) showed that the abundances of Vibrio both in the water and gut were negatively correlated with CS-GT dosage. In conclusion, the oral administration of CS-GT can improve the immunity of shrimp against pathogenic bacteria and significantly reduce the relative abundances of Vibrio in aquaculture water and the gut of Litopenaeus vannamei.
Highlights
Shrimp farming is one of the most important industries in the world [1,2]
The physical–chemical constituents of the water often directly promote the growth of Litopenaeus vannamei, and ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen are important standards for monitoring water quality
(supplemented with CS after infection with Vibrio parahaemolyticus) groups were measured every day during the experiment
Summary
Fast growth, and easy adaptability, Pacific white shrimp (Litopenaeus vannamei) have become one of the most profitable species in shrimp farming, with an annual global production of more than 4.1 million tons [3]. This accounts for 73% in China [4]. The Pacific white shrimp belongs to temperate and tropical shrimp. It can survive in the temperature of 10–40 ◦ C, and the most suitable temperature range is 25–32 ◦ C. Pacific white shrimp lack adaptive immune mechanisms and depend on innate immune responses for the detection and elimination of
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