栉孔扇贝雌核发育二倍体早期成活与生长发育的研究

Studies on Early Survival and Growth of Gynogenetic Diploids in the Scallop,Chlamys farreri

利用筛选出的精子遗传失活法和卵染色体加倍法,批量诱导出第二极体抑制型栉孔扇贝雌核发育二倍体个体,观测了幼体不同发育时期的成活率、发育速度和个体大小等生物学特性。结果发现,雌核发育二倍体的卵裂率、胚胎畸形率、D形幼虫发生率、孵化后3,6,9,12,15,18 d的成活率均显著低于对照组,表明栉孔扇贝基因组中可能存在大量有害隐性基因,雌核发育个体中有害隐性基因的纯合导致了成活率的显著下降。在发育速度方面,D形幼虫期之前,雌核发育二倍体个体明显低于对照组个体;壳顶期后则相反,雌核发育二倍体个体高于对照组个体。在个体大小方面,雌核发育二倍体个体在孵化后3 d前,壳长和壳高均小于对照组个体;孵化3 d后,壳长和壳高逐渐大于对照组个体。这一结果显示随着致死隐性基因因纯合而被自然排除,雌核发育二倍体的生长性状逐渐优越于正常个体,通过将这些雌核发育二倍体个体培养至成体,则可望培育出栉孔扇贝的优良品系。

By using the techniques of genetic inactivation of sperm and chromosome doubling by suppressing secorid body formation with 6-dimethylaminopurine treatment, we produced gynogenetic diploid individuals in the scallop Chlamys farreri, and examined their performance in early survival and growth. The rates of cleavage, embryo abnormality, development of D-larvae, and survival on day 3, 6, 9, 12, 15 and 18 post-hatching were significantly lower than those in the control group, suggesting that a large number of deleterious recessive genes existed in the scallop genome, and the homozygosity of the deleterious recessive genes resulted in the low viability of gynogenetic diploids. Compared with that in the control group, the developmental speed in the gynogenetic diploid group was significantly slower before D-larvae stage, but became obviously higher after umbo-larvae stage. Compared with that of normal diploids, the size of gynogenetic diploid individuals was smaller before day 3 post-hatching, but thereafter became bigger significantly after day 3 post-hatching. The results indicate-that following the elimination of the lethal recessive genes for homozygosity, the performance of gynogenetic diploids in growth was markedly superior to that of the control, suggesting that an excellent line can be created if the gynogenetic diploid individuals survive to adulthood.