Hatchery-scale trials using cryopreserved spermatozoa of black-lip pearl oyster,

Cryopreservation is a valuable tool for genetic improvement programs. Several bivalve mollusc species have already been the subject of such programs and the Tahitian black pearl oyster industry is now planning the development of selective breeding for desirable traits in Pinctada margaritifera. The ability to cryopreserve spermatozoa would, therefore, offer significant benefits to the cultured black pearl industry. Spermatozoa were cryopreserved with cryoprotectant agent (CPA) 0.7 M trehalose in 0.8 M Me2SO and a two-step freezing process was used: straws were first maintained in nitrogen vapour for 10 minutes, then directly plunged into liquid nitrogen and stored for one week before use. The viability of thawed sperm was 23% lower than that of fresh sperm. When using thawed sperm, therefore, a higher sperm/egg ratio of 100 000:1 was required to reach 80% oocyte fertilization, compared with 100:1 for fresh sperm. Nevertheless, this first demonstration of cryopreserved sperm fertility in black pearl oyster confirms the hatchery applicability of the cryopreservation technique defined here. Monitoring for larval viability during the first 23 days of life revealed no significant differences between the progeny produced with cryopreserved sperm and that produced using fresh sperm.