Effects of
developmental stage, seawater concentration and rearing temperature on
cryopreservation of Pacific oyster Crassostrea gigas larvae
H. Usuki, M. Hamaguchi, H. Ishioka-2002
Fisheries
Science,
68(4): 757-762
Abstract:
For the development of a stepwise
cryopreservation technique for larvae of the Pacific oyster Crassostrea
gigas, various conditions were examined. Larvae at 9, 12, 15, 18 and 21 h
after insemination were cooled at a rate of -1°C/min (seeding at -8°C for
15 min) and then plunged into liquid nitrogen at -35 or -40°C using
1.5 M dimethyl sulfoxide (DMSO) and 250 mM trehalose as
cryoprotectants. Among these larvae, 15 h after insemination (the
trochophore stage before formation of the shell gland) showed the highest
motility and the best external appearance after thawing. Trochophore larvae
were cryopreserved in preservation media containing different dilutions
(1/4, 1/6, 1/8, 1/10 and 1/30) of seawater. Larvae preserved in the 1/4
seawater medium showed the highest appearance of shelled larvae 4 days after
thawing. Trochophore larvae reared in seawater at 21, 25 or 29°C were
cryopreserved for 8 months and then reared at 26°C after thawing. Larvae
reared at 25°C showed the highest survival rate and normal larval ratio at
day 6 after thawing, although larvae reared at 21°C showed the highest
rates until day 4. One larva developed at 25°C succeeded to settle.
(National Research Institute of Fisheries and
Environment of Inland Sea, Ohno, Hiroshima 739-0452, Japan, Tel:
81-829-55-0666. Fax: 81-829-54-1216. Email: usuki@fra.affrc.go.jp)