热休克诱导鳙鱼四倍体的研究

TETRAPLOIDY INDUCED BY HEAT SHOCK IN BIGHEAD CARP, ARISTICHTHYS NOBILIS

采用热休克法研究了诱导鳙鱼四倍体的可能性和处理条件。结果表明:1)恰好在卵子开始第一次卵裂前用39—42℃水浴处理1—3分钟,可获得较高频率的四倍体;2)开始处理的时间至关重要,提前或推迟处理导致几乎全部死亡或四倍体频率大大下阵;3)热休克组的孵化率显著下降,畸形率明显升高;4)含高频率四倍体的热休克组的细胞分裂和胚胎发育延迟。

Tetraploidy was successfully induced through suppression of first cleavage using heat shocks in bighead carp, Aristichthys nobilis. The first cleavage division occured around 55 min. after fertilization when temperature = 22cccccccccccccc. Shocks applied at 50 min postfertilization (shortly before first cleavage) at 41-41.5ccccccccccccccccccccc lasting 1.5-2 min induced repeatedly the satisfactory high yields of tetraploid embryos and hatched fry (maximum 56.35%, Table 1) with acceptable survival at hatching, while shocks at higher temperatures or for longer durations resulted in increased abnormality and nearly complete mortality. The eggs in the groups shocked earlier (at 45 min postfertilization) contained few tetraploids and failed to pass through gastrulation, and eggs in the groups shocked later (at 55 min), showing the lower hatchability similar to that of the eggs shocked at 50 min postfertilization, gave much decreased tetraploid yields. Delaved cell division and embryogenesis were expectantly observed in large number of the eggs or embryos of the heat-shocked groups which would give rise to large proportion of tetraploids (Table 4.). Either normal or abnormal fry hatched from heat-shocked eggs consisted of both tetra and diploids with similar ratios, while those from control contained diploids only.The results obtained demonstrate that: 1) Heat shock is rather effective in inducing tetrap-loidy in bighead through suppression of first cleavage; 2) The eggs of bighead are sensitive to such heat shocks only in a very short period of their early development, consequently, exact starting time of heat shock is critical for successful suppression of first cleavage, 3) Delayed cell division could be roughly used to evaluate induction effectiveness of heat treatments; and 4) The heat-induced autotetraploids of bighead showed the viability similar to that of heat-treated diploids at least during their embryogenesis and shortly after hatching, yet both the heat-shocked tetra and diploids were subvital compared to their control diploids, indicating that lower hatchability and higher abnormality in the heat-shock groups might be largely due to the damages in the eggs caused by heat treatments.