Effect of diurnal oxygen variation on gene expression in Pacific white shrimp reared in green water system tanks
World aquaculture production of the Pacific white shrimp (Litopenaeus vannamei) is estimated to account for 80% of the total shrimp produce worldwide. The global demand for shrimp has driven the industry to utilize and rely on semi-intensive and intensive shrimp systems. In the United States, Pacific white shrimp production can take place in semi-intensive earthen ponds, recirculating aquaculture systems (RAS), biofloc technology and green water. In this study, the effects of lowering dissolved oxygen conditions in outdoor green water tanks on global gene expression is examined. Tissue samples from the gill and intestine were collected for gene expression analysis via RNA sequencing. Among all comparisons, RNA sequencing revealed the up-regulation of a single gene: hydroxyacid oxidase 1 gene. The HOA1 gene was found to be 7-fold higher in the intestine sample at the medium aeration level compare to that of the high (control) level. The HAO1 gene, also known as glycolate oxidase 1 (GOX1) is a gene related to the 2-hydroxyacid oxidase enzyme that is part of the oxidoreductase family and plays a role in glyoxylate and dicarboxylate metabolism. The identification of a single differentially expressed gene across all analyzed samples suggests that Pacific white shrimp exposed to lowering dissolved oxygen set points does not induce global changes in gene expression at these levels. Overall design: Twelve (800 L) round tanks were stocked each with 35 shrimp (1.99 ± 0.06g) and reared in 15 ppt green water system tanks for 6 weeks. Four of the tanks were aerated at 0.25 cubic feet per second (cfs; low), four at 0.35 cfs (medium) and four at 0.7 cfs (high). The experiment was terminated 42 days after stocking, when two shrimp per tank were randomly collected, and gill (fourth gill filament from one side) and intestine were extracted and preserved in DNA/RNA shield (ZYMO Research, Irvine, CA, USA) for RNA sequencing.