Rearing effect of biofloc on antioxidant and antimicrobial transcriptional response in Litopenaeus stylirostris shrimp facing an experimental sub-lethal hydrogen peroxide stress

This study compares the antioxidant and antimicrobial transcriptional expression of blue shrimps reared according to two different systems, BioFloc Technology (BFT) and Clear sea Water (CW) and their differential responses when facing an experimental sublethal hydrogen peroxide stress. After 30 days of rearing, juvenile shrimps were exposed to H2O2 stress at a concentration of 30 ppm during 6 hours. The oxidative stress caused by H2O2 was examined in the digestive glands of the shrimp, in which antioxidant enzyme (AOE) and antimicrobial peptide (AMP) gene expression were analysed by quantitative real-time PCR. Results showed that rearing conditions did not affect the expression of genes encoding AOEs or AMPs. However, H2O2 stress induced a differential response in expression between shrimps from the two rearing treatments (BFT and CW). Comparative analysis of the expression profiles indicates that catalase transcripts were significantly upregulated by H2O2 stress for BFT shrimps while no change was observed for CW shrimps. In contrast, H2O2 caused down-regulation of superoxide dismutase and glutathione transferase transcripts and of the three AMP transcripts studied (penaeidin 2 and 3, and crustin) for CW shrimps, while no effect was observed on BFT shrimp transcript levels. These results suggested that BFT shrimps maintained antioxidant and AMP responses after stress and therefore can effectively protect their cells against oxidative stress, while CW shrimp immune competence seems to decrease after stress.

Energy and Antioxidant Responses of Pacific Oyster Exposed to Trace Levels of Pesticides

Here, we assess the physiological effects induced by environmental concentrations of pesticides in Pacific oyster Crassostrea gigas. Oysters were exposed for 14 d to trace levels of metconazole (0.2 and 2 mu g/L), isoproturon (0.1 and 1 mu g/L), or both in a mixture (0.2 and 0.1 mu g/L, respectively). Exposure to trace levels of pesticides had no effect on the filtration rate, growth, and energy reserves of oysters. However, oysters exposed to metconazole and isoproturon showed an overactivation of the sensing-kinase AMP-activated protein kinase alpha (AMPK alpha), a key enzyme involved in energy metabolism and more particularly glycolysis. In the meantime, these exposed oysters showed a decrease in hexokinase and pyruvate kinase activities, whereas 2-DE proteomic revealed that fructose-1,6-bisphosphatase (F-1,6-BP), a key enzyme of gluconeogenesis, was upregulated. Activities of antioxidant enzymes were higher in oysters exposed to the highest pesticide concentrations. Both pesticides enhanced the superoxide dismutase activity of oysters. Isoproturon enhanced catalase activity, and metconazole enhanced peroxiredoxin activity. Overall, our results show that environmental concentrations of metconazole or isoproturon induced subtle changes in the energy and antioxidant metabolisms of oysters.