Effects of phosphatidylcholine and tocopherol during larval cryopreservation of Pacific oysters (Magallana gigas)

Pacific oysters are among the most important shellfish aquaculture species worldwide. Gamete and larval cryopreservation are promising techniques that could be used in genetic conservation to address industry issues, such as off-season breeding, asynchronous gonad development, and biosecurity concerns over stock relocation. Larval cryopreservation can also preserve both maternal and paternal genomes. This study investigated whether existing larval cryopreservation techniques could be improved by supplementing the base cryoprotective agent (CPA) with an exogenous lipid or antioxidant. The results show that adding 0.5 mg·mL⁻¹ of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC; lipid) to the base CPA significantly increased the proportion of post-thaw larvae that developed into D-stage larvae, whereas the addition of tocopherol (an antioxidant) alone had no significant effect on post-thaw larval performance. The relative survival rate (adjusted by the rate in the control of ∼84%) of D-stage larvae was improved to ∼90% in the larvae cryopreserved by adding both 0.25 mg·mL⁻¹ POPC and 1 mg·mL⁻¹ tocopherol into the base CPA, resulting in double the amount of spat produced (8.47%) in comparison to those cryopreserved with the base CPA (4.33%). This study provides a new approach for improving larval cryopreservation of bivalve species.