Kawamura Kazuo, Fujita Hiroko, Nakauchi Mitsuaki
Department of Biology, Faculty of Science, Kochi University, Kochi 780, Japan.
Dev Growth Differ. 1987 Nov;29(6):627-642. doi: 10.1111/j.1440-169X.1987.00627.x.
We have determined how many elements are involved in the regulation of self-fertilization in the solitary ascidian, Ciona intestinalis that is an incompletely self-sterile species. Animals collected in the field were repeatedly induced to spawn in order to examine their selfing ratios. About 20% of them were self-fertile, although the ratios fluctuated considerably among respective spawnings. Naturally or acid-induced self-fertile gametes required much longer time for selfing than that for crossing. Egg-suspending seawater (egg water) as such activated sperm motility, but it lowered conspicuously the self-fertilization ratio. Self-sterile spermatozoa could scarcely bind to the vitelline coat (VC) of glycerinated autologous eggs. or in case they bound well to it the sperm flagella ceased to beat within five min of the 'insemination'. The staining of sectioned gametes with DAPI, a fluorescent dye of DNA, showed that in selfing the spermatozoa could hardly penetrate the VC even though they bound well to it. The results of this study show that the block of self-fertilization can be classified into four elements from a phenomenal viewpoint, such as egg water, low affinity of sperm-VC binding, inactivation of bound sperm and difficulty in sperm penetration through the VC.
我们已经确定在单体海鞘（Ciona intestinalis）这种不完全自交不育的物种中，有多少种因素参与了自体受精的调控。采集自野外的动物被反复诱导产卵，以检测它们的自交率。尽管每次产卵时自交率波动很大，但约20%的个体是自交可育的。自然产生或经酸诱导产生的自交可育配子进行自体受精所需的时间比异体受精长得多。这样的悬浮卵子的海水（卵水）能激活精子活力，但会显著降低自体受精率。自交不育的精子几乎无法与甘油处理的自体卵子的卵黄膜（VC）结合，或者即使它们能很好地结合，精子鞭毛在“授精”后五分钟内也会停止摆动。用DNA荧光染料DAPI对切片配子进行染色显示，在自体受精过程中，精子即使能很好地与卵黄膜结合，也很难穿透卵黄膜。本研究结果表明，从现象学角度来看，自体受精的障碍可分为四个因素，即卵水、精子与卵黄膜结合的低亲和力、结合精子的失活以及精子穿透卵黄膜困难。
