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