Cryoprotectant optimization for sperm of diploid Pacific oysters by use of commercial dairy sperm freezing facilities

Document Type

Article

Publication Date

10-3-2007

Abstract

Although sperm cryopreservation has been practiced in aquatic species for more than 50 years, viable markets for frozen sperm do not currently exist for commercial aquaculture. The present study suggests that the use of commercial cryopreservation facilities used for dairy bulls could be a cost-effective approach to initiate commercialization of frozen sperm in aquaculture, and the oyster industry could become one of the early adopters. To prove the technical feasibility of the use of a commercial freezing facility, this study adopted dairy freezing methods and emphasized cryoprotectant optimization for sperm from diploid Pacific oysters Crassostrea gigas with specific cooling methods employed for use with bull sperm. Specifically, the present study evaluated dimethyl sulfoxide (DMSO) at 5, 8, and 10%, ethylene glycol (E-glycol) at 2, 5, 8, and 10%, and methanol at 2, 4, 6, and 8%. Each cryoprotectant with its optimal concentration was chosen for subsequent selection of an optimal cryoprotectant. Previous results showed propylene glycol (P-glycol) at 5% yielded higher percent fertilization than did PG at 10 or 15%. Therefore, 5% of these cryoprotectants were compared and the highest percent fertilization was obtained with methanol (49 ± 29%), followed by E-glycol (42 ± 15%), DMSO (31 ± 18%), and P-glycol (22 ± 12%). Extensive evaluation for single and combined cryoprotectants and their concentrations were studied in our previous trials on a research scale (reported elsewhere), and 6% methanol and the combination of 4% methanol and 2% polyethylene glycol (PEG; FW 200) were shown to consistently yield the highest percent fertilization. Our last commercial-scale experiment compared 6% methanol with the combination of 4% methanol and 2% PEG (MET/PEG) with 20 oysters. There was no significant difference for percent fertilization between 6% methanol (39 ± 29%) and 4% MET/2% PEG (42 ± 26%). These findings demonstrate the technical feasibility of adopting dairy freezing protocols in commercial application for oyster sperm, and also provide a template for future commercialization of sperm cryopreservation for other aquatic species. © 2007 Elsevier B.V. All rights reserved.

Publication Source (Journal or Book title)

Aquaculture

First Page

537

Last Page

545

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