Effect of cyclic serious/medium hypoxia stress on the survival, growth performance and resistance against Vibrio parahemolyticus of white shrimp Litopenaeus vannamei
Keywords:Litopenaeus vannamei, cyclic serious/medium hypoxia, mortality, growth performance, histology, Vibrio parahaemolyticus
The effect of cyclic serious/medium hypoxia stress in the presence of hypoxia environment on shrimp is not well explored. The survival, growth performance, osmoregulation gene expression, digestive enzyme activity, histology, and resistance against Vibrio parahemolyticus of the white shrimp Litopenaeus vannamei reared under conditions of cyclic serious/medium hypoxia (CSMH, 0.8 - 3.5 mg/L) versus normoxia (N, 6.4 - 7.5 mg/L) were investigated during an experimental period of 28 days. Consequently, the cumulative mortality rate of CSMH shrimp increased continuously. The weight gain percentage and length gain percentage of CSMH shrimp decreased continuously. The Na+/K+-ATPase, cytoplasmic carbonic anydrase (CAc), and glycosyl-phosphatidylinositol-linked carbonic anhydrase (CAg) transcripts in the gill of CSMH shrimp increased first and then returned to normal or decreased. The amylase, lipase, and trypsin activities in the hepatopancreas of CSMH shrimp decreased continuously. The hepatopancreas of CSMH shrimp showed histopathological lesions in a time-dependent manner. In the V. parahaemolyticus immersion challenge test, the mortality rate of CSMH shrimp increased continuously. Therefore, cyclic serious/medium hypoxia could reduce survival and growth performance of L. vannamei during long-term exposure, which was resulted from broken osmoregulation mechanism of the gill, and suppressed digestive enzyme activities of the hepatopancreas caused by growing histopathological lesions. Meanwhile, cyclic serious/medium hypoxia would probably lead to outbreak of infectious diseases in the shrimp farming.