平鲷雌核发育二倍体的人工诱导

Artificial induction of gynogenesis in silver sea bream(Rhabdosargus sarba)

平鲷(Rhabolosargus sarba)养殖群体具有雌性生长优势的特点.应用冷休克方法进行平鲷雌核发育二倍体人工诱导,采用高温消毒的自然海水为精子稀释液,精液经强度为700μW/(cm2.s)的紫外线(UV)照射100 s,染色体遗传物质失活,卵子经激活后,可以获得95%～100%单倍体胚胎.实验结果表明:在卵子激活后5 min进行冷休克,温度0～8℃,处理时间持续15min,雌核发育二倍体的受精率达71.3%～82.7%,孵化率为24.7%～36.3%,2～6℃为适宜冷休克温度,此范围内的温度对雌核发育二倍体的受精率和孵化率没有显著影响(P>0.05),而与0,1和8℃实验组的受精率和孵化率差异均显著(P<0.05);在冷休克温度为3℃、持续时间为15 min的条件下,初始冷休克时间在4～6 min之间的受精率和孵化率均较高,分别达到60.0%～67.1%和30.6%～36.5%,其组间受精率和孵化率没有显著差异(P>0.05),而与其他实验组的孵化率存在显著差异(P<0.05);冷休克持续时间以11～19 min为宜,受精率和孵化率分别为46.9%～65.8%和31.7%～42.4%,在此时间内,冷休克持续时间对平鲷的雌核发育二倍体受精率和孵化率影响不显著(P>0.05).选用冷休克温度、初始冷休克时间和持续时间分别为3℃,5和15 min作为平鲷雌核发育二倍体的诱导条件是显著有效的.

The silver sea bream（ Rhabdosargus sarba） is a valuable fishery and aquaculture species in Asia, with sexually dimorphic growth in favor of the females. Gynogenetic diploids were induced using UV--irradiated sperm of conspecifics and cold shock. In the experiments, the sperm was diluted in 1 ： 60 in disinfected natural seawater and then irradiated for 100 s at a UV intensity of 700 μW/（cm^2· s）. This irradiation duration inactivated the spermatozoa genetically but still maintained their physiological vitality to activate eggs. 95%~100% of haploid rate was obtained when non cold shock was used. Suitable conditions of time to initiate cold shock, cold shock temperature and duration to restore the diploidy were evaluated. The results showed the fertilization rate and hatching rate of gynogenetic diploid were 71.3%~82.7% and 24.7%~36.3%, respectively by applying cold shock at 0~8℃ to eggs activated with UV--irradiated homologous sperm, 5 min after activation, with shock duration of 15min. The optimum cold shock temperature was 2~6 ℃. 60.0%~67.1% fertilization rate and 30.6%~36.5% hatching rate was attained starting cold shock 4~6 min after fertilization, cold shock at 3 ℃ for 15 min. Cold shock duration of 11~19 min was appropriate in inducing gynogenesis, which resulted in 46.9% ~65.8% fertilization rate and 31.7%~42.4% hatching rate. The results of experiments indicated that eggs were exposed to a cold shock at 3 ℃, 5 min after activation with shock duration of 15min was significantly effective for induction of diploid gynogenesis in silver sea bream. Mass production of diploid gynogenetic fry is possible in this prolific species.