Investigation on redox status and gene expression related to larval cryopreservation in the Pacific oyster Crassostrea gigas

This study evaluated the effects of larval cryopreservation on redox status of post-thaw trochophore larvae and on gene expression in post-thaw trochophore larvae, D-larvae, umbo larvae, eyed larvae and spat, with the aim to understand the effects of cryodamage in the Pacific oyster Crassostrea gigas. The results showed that total antioxidant capacity was significantly higher in the cryopreserved larvae than in the control group (P < 0.05), with no significant difference in the production of reactive oxygen species between these two groups (P > 0.05). The expressions of FADD, Bax1, Baxlike, Bcl2, CASP7 and CAT were significantly downregulated in post-thaw trochophore larvae, whereas the expression of the SOD gene was significantly upregulated. However, the expressions of all of these genes did not significantly differ at later developmental stages. In the cryopreserved group, the expressions of GPX and ATG6 were downregulated in trochophore larvae and upregulated in D-larvae, while there were no signficant changes in the expressions of BI-1, Caspase 3 and ATG8 at all developmental stages investigated. Taken together, these results suggest that the larval cryopreservation technique developed for the Pacific oyster may compromise the survival of post-thaw trochophore larvae by modifying the redox status and gene expression patterns, but that they have limited effects, if any effect at all, after the umbo stage, indicating that the umbo stage should be used for assessing post-thaw larval performance in this species.