Aestivation is a kind of dormancy that is probably defined as a survival strategy for dealing with arid conditions,food shortage and high environmental temperature.As an adaptation for life in stressful environments,multiple adjustments occurred in aestivated organism including the regulation of defense system.Antioxidant enzymes are regulated in aestivating animals usually.To evaluate the transcriptional regulations associated with antioxidant defense in sea cucumber during aestivation,gene expression of antioxidant enzymes in respiratory tree was analyzed in this study.Five partial sequences of antioxidant enzyme genes were obtained from Apostichopus japonicus transcriptome database:Cu/Zn-SOD(copperzinc superoxide dismutase),CAT(catalase),PHGPx(Phospholipid hydroperoxide glutathione peroxidas),PRDX5(Peroxiredoxin5)and PRDX6(Peroxiredoxin6).The multiple sequence alignment(MSA)was conducted and special primers were designed for Real-time PCR assay.These genes expressions were normalized by multiple internal control genes of NDUFA13(NADH dehydrogenase［ubiquinone］1 alpha subcomplex subunit 13)and ACTB(beta actin),and their variations during aestivation of A.japonicus were analyzed.Compared with the active sea cucumbers (sampled in May),the antioxidant enzymes got transcriptional change in respiratory tree of aestivated sea cucumbers(sampled in Aug):the expression of Cu/Zn-SOD genes got increase to 1.66 fold(P>0.05);the expression of PRDX5 genes got significant increase to 1.69 fold(P<0.05);the expression of CAT and PHGPx got significant decrease to 0.60 and 0.38 fold respectively (P<0.05);no notable expression variation of PRDX6 was found.It was mainly consistent with the variation of these genes expressions in later phase of thermal induced aestivation of A.japonicus(aestivated sea cucumbers sampled on 40 d):the expressions of Cu/Zn-SOD and PRDX5 genes got significant increase to 1.85 and 1.91 fold respectively(P<0.05);the expressions of CAT and PHGPx genes got significant decrease to 0.60 and 0.34 fold respectively(P<0.05);no notable expression variation of PRDX6 was found.The result indicated that the gene expressions of different antioxidant enzymes were regulated differently during aestivation of sea cucumber.