Varieties of immunity activities and gut contents in tilapia with seasonal changes

We performed 16S rDNA sequencing of tilapia fecal samples to analyze changes in tilapia gut contents after cultivation of the fish in the presence of sandwich-like floating beds of Chinese medicinal herbs (5 and 10% planting-areas; 5% Polygonum cuspidatum). The interactive effects between water quality and blood and hepatic pro- and anti-inflammatory concentrations were also assessed. Our results showed that the water quality (i.e., NO3--N, NO2--N, TP removal rates) improved, and the abundance of Chloroflexi and Cyanobacteria increased. The abundance of Bacteroidetes, Verrucomicrobia, Saccharibacteria, and Actinobacteria showed both significant seasonal decreases and increases in the presence of P. cuspidatum (increases in August and decreases in July). Fish blood and hepatic IL-10 and IFN-gamma levels (together with fish sampled in September) significantly increased in the P. cuspidatum group sampled in August, while those of TNF-alpha (10% sandwich-like, P. cuspidatum), IL-1 beta (P. cuspidatum), IL-8 (5% sandwich-like in September, S905S) significantly decreased. Heat shock proteins 60 and 70 levels significantly increased in the P. cuspidatum group, and complement C3 and C4 concentrations significantly increased in S905S. This study demonstrated that enhanced immunity through the regulation of pro- and anti-inflammatory proteins was sustained throughout development until harvest, particularly in fish grown with P. cuspidation.