Seasonal Variation Of Gut Cyanophyta Contents And Liver GST Expression Of Four Freshwater Fishes In Tropical Xiangang Reservoir (Huizhou, China)

The information on the relationship of fish gut Cyanophyta contents and liver glutathione S-transferase (GST) expression is important to understand the detoxification of microcystins (MCs) in liver via conjugation to glutathione (GSH) by GST. In this study, the water and gut contents of mud carp (Cirrhina molitorella), Nile tilapia (Oreochromis niloticus), sliver carp (Hypophthalmichthys molitrix) and grass carp(Ctenopharyngodon idella) were studied in tropical Xiangang Reservoir between Otc.2007 and Jul.2008. Meanwhile, the variation in the transcription of several liver GST genes was determined by real-time RT-PCR. Expression of the liver GST in Nile tilapia showed a positive correlation to quantity of toxic cyanobacteria in gut contents, whereas expression of the liver GST in mud carp showed a negative correlation to quantity of toxic cyanobacteria in gut contents. The results also showed that the relative liver GST mRNA abundance had a positive correlation with the Cyanophyta quantity in the gut contents of sliver carp as well as in the water contents which grass carp might contact with. We suggested that the different correlation between expression of the liver GST and gut toxic cyanobacteria contents in the four fishes depending on their resistance to MCs.