Experimental obtaining the polyploid Pacifi c oyster Crassostrea gigas (Thunberg, 1793) via a heat shock

Method of thermal induction was tested for the first time in the practice of Far Eastern aquaculture to obtain polyploid Pacific oyster Crassostrea gigas . Experimental blocking of meiosis was performed 25 min after fertilisation by brief (3 min) exposure to the temperature of 32 o C. Efficiency of the method was evaluated with assessment of survival, growth and development of control and experimental larvae (groups 2N and 3N, respectively) in conditions of plant. Growth rate of juvenile Crassostrea gigas in Voyevoda Bay, Russky Island (Peter the Great Bay, the Sea of Japan) during two years was studied also. The content of DNA in haemocytes evaluated using flow cytometry revealed 35% triploids, 22.5% tetraploids and 40% heteroploids in the group 3N. The maximum weight increment in this group (0.34 g/day) was observed in summer at the second year of life, and the maximum linear growth rate (1.55 mm/day) – in September at the second year. The values for the group 2N were 0.31 g/day and 1.47 mm/day respectively. After 22 months, 57.9% of diploid and 80.9% of polyploid oysters reached their commercial size. The total weight of oysters in the group 3N was 124.6 ± 2.7 g, what was 43% more compared to the group 2N.