Successful oocyte cryopreservation in the blue mussel Mytilus galloprovincialis

• This is the first report on successful oocyte cryopreservation in blue mussels.
• A D-larval rate of approximately 14% was achieved with cryopreserved oocytes.
• No significant difference in performances was found between progenies produced with cryopreserved and fresh oocytes from D-larval stage to spat.

The development of oocyte cryopreservation techniques is widely acknowledged being very difficult in aquatic species and has only been successfully achieved in Pacific oysters Crassostrea gigas. Results from published data have shown that oocyte cryopreservation in other bivalve species (including blue mussels Mytilus galloprovincialis) is challenging with, if any, very limited D-larvae having been produced. In this study, a technique to cryopreserve blue mussel oocytes has been developed through investigating the effects of polysaccharide and sugar at cryopreservation and post-thaw cryoprotectant agent (CPA) removal, respectively. The highest post-thaw D-larval rate of 14% was achieved when mussel oocytes were cryopreserved in the CPA consisting of 10% ethylene glycol + 7.5% Ficoll PM 70 and post-thaw CPA was removed by 9% sucrose. Over the subsequent development to spat stage, the performances (survival and growth rates) of the progenies produced with cryopreserved oocytes were similar to controls.