凡纳滨对虾胚胎发育进程及诱导染色体加倍时间确定

Observation of embryonic development and determining time of inducing chromosome doubling in Litopenaeus vannamei

[目的]了解凡纳滨对虾胚胎发育的时序及特征,为其雌核发育诱导中染色体加倍最佳操作窗口的确定及人工苗种生产提供参考依据.[方法]以人工培育成熟凡纳滨对虾“桂海1号”的受精卵为研究对象,观察并描述不同水温下卵子从产出受精至幼体孵化出膜的整个胚胎发育过程.[结果]根据凡纳滨对虾胚胎发育的形态特征变化,可分为7个阶段：受精卵期、卵裂期、囊胚期、原肠期、肢芽期、膜内无节幼体期和出膜幼体期.凡纳滨对虾受精卵在水温30.5℃、盐度28.6‰的条件下,整个胚胎发育过程需11.5～11.8 h.水温变化对凡纳滨对虾受精卵极体的排出和孵化时间有明显影响,水温每下降1℃,孵化时间需增加0.6h;在28.0～30.5℃的水温范围内,受精卵第一极体释放时间为7～13 min,第二极体释放时间为8～14 min,整个胚胎发育过程需11.5～13.0 h.其中,在30.5℃的水温条件下,第一极体释放的时间为7～9 min,第二极体释放的时间为8～10 min,即在水温30.5℃、盐度28.6‰的条件下,凡纳滨对虾受精卵染色体加倍诱导的最佳时间在卵子受精后8～10 min.[结论]在确保凡纳滨对虾受精卵正常发育的前提下,适当调低培育水温能延迟胚胎发育速度,为人工诱导受精卵染色体加倍创造较充足的操作窗口期.此外,受精卵是否均等分裂是判断凡纳滨对虾卵子受精与否的重要标准.

[Objective]The timing and characteristics of embryonic development of Litopenaeus vannamei were studied to provide references for suitable operating time of artificial chromosome doubling in subsequent gynogenetic induction and artifi- cial seed production. [Method]Oosperms from mature artificial cultivated Litopenaeus vannamei Guihai 1 was used as the research objects. The whole process of embryonic development, from egg laying up to larva hatching, was observed and de- scribed at different temperature. [Result] According to the morphological changes, the embryonic development of Ltiopenaeus vannamei could be divided into the following seven stages： germinal stage, cleavage stage, blastula stage, gastrula stage, limb bud stage, intramembrane nauplius stage and nauplius stage. The whole process of embryonic development endured 11.5-11.8 h. Water temperature variation significantly affected polar body releasing and hatching time of oosperm. Every time water tem- perature fell by 1℃, hatching time increased by 0.6 h. At water temperature range of 28.0-30.5 ℃, the first polar body exclu- sion time of oosperm was 7-13 min, the second polar body exclusion time of oosperm was 8-14 min and the whole process of embryonic development took about 11.5-13.0 h. At the temperature of 30.5 ℃, the first and second polar body exclusion time of oosperm was 7-9 and 8-10 min, respectively. At the temperature of 30.5 ℃ and salinity of 28.6%, 8-10 min after egg exclu- sion was the optimal time for inducing chromosome doubling in Litopenaeus vannamei. [Conclusion]Under the premise of normal development of oosperms, appropriately reducing water temperature could delay the development process and createmore adequate operating window for artificial induction of chromosome doubling in Litopenaeus vannamei. Even split could be used as an important standard for judging the oosperm and unfertilized egg of Litopenaeus vannamei.