Laboratory of Fish Immunology and Genetics, Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
Theor Appl Genet. 1988 Aug;76(2):253-9. doi: 10.1007/BF00257853.
In this study, a Hertwig effect with a non-typical biphasic curve was obtained using sperm irradiated with increasing intensities of UV. The first phase of the UV curve appeared to be quite different from that normally demonstrated using γ or x-ray irradiation. This difference is characterised throughout the length of the first phase by (1) low and stable embryo hatching rates of about 3.5%, and (2) exclusive formation of haploid embryos at any irradiation intensity. Additionally, at both phases, the ability of the sperm to induce morula formation was not affected at all, and no aneuploidy nor chromosomal fragments could be seen. Therefore, it was suggested that in this fish the lethal effect of UV irradition on sperm is mainly expressed on early differentiative events during embryogenesis, which lead to a degeneration of the embryos during early stages of their development. The possible mechanism by which haploidy is achieved during the first phase is discussed. Two generations of diploid gynogenetic tilapias were induced by activating Oreochromis aureus eggs with UV-irradiated O. niloticus sperm and by using the heat-shock technique, at optimized conditions, for the prevention of the second polar body extrusion. Species specific dominant genetic markers (serum esterases and tail striation) were used to confirm the exclusive content of the maternal genome in gynogenetic offspring. Very low survival rates (0.36%) were shown in F1 gynogenetic fish as well as a high incidence of malformations among survivors. In the second gynogenetic generation, both significantly higher survival rates (3.6%) and a considerably reduced incidence of malformations were obtained. We suggest that low frequencies of recombination occur in this species and cause a rapid increase in the inbreeding level. This is followed by the expression of lethal and defective genes that are considerably reduced after second generation selection.
在这项研究中，使用不同强度紫外线照射精子获得了具有非典型双相曲线的赫特维希效应。紫外线曲线的第一阶段似乎与通常使用γ射线或 X 射线照射所表现出的阶段完全不同。这种差异在第一阶段的整个长度上都表现为：（1）孵化率低且稳定，约为 3.5%，（2）在任何辐射强度下，仅形成单倍体胚胎。此外，在两个阶段，精子诱导桑椹胚形成的能力都没有受到影响，也没有观察到非整倍体或染色体片段。因此，在这种鱼类中，紫外线照射对精子的致死效应主要表现在胚胎发生过程中的早期分化事件上，这些事件导致胚胎在其发育的早期阶段退化。讨论了在第一阶段实现单倍体的可能机制。通过用紫外线照射的奥利亚罗非鱼精子激活奥利亚罗非鱼卵子，并在优化条件下使用热休克技术防止第二极体排出，诱导了两代二倍体雌核发育罗非鱼。使用种特异性显性遗传标记（血清酯酶和尾部条纹）来确认雌核发育后代中仅含有母本基因组。在 F1 雌核发育鱼中显示出非常低的存活率（0.36%），以及幸存者中畸形的高发率。在第二代雌核发育中，存活率显著提高（3.6%），畸形发生率显著降低。我们认为，这种物种中重组频率较低，导致近交水平迅速增加。随后是致死和缺陷基因的表达，在第二代选择后显著减少。
