One of the earliest and most prevalent barriers to successful reproduction is polyspermy, or fertilization of an egg by multiple sperm. To prevent these supernumerary fertilizations, eggs have evolved multiple mechanisms. It has recently been proposed that zinc released by mammalian eggs at fertilization may block additional sperm from entering. Here, we demonstrate that eggs from amphibia and teleost fish also release zinc. Using Xenopus laevis as a model, we document that zinc reversibly blocks fertilization. Finally, we demonstrate that extracellular zinc similarly disrupts early embryonic development in eggs from diverse phyla, including Cnidaria, Echinodermata, and Chordata. Our study reveals that a fundamental strategy protecting human eggs from fertilization by multiple sperm may have evolved more than 650 million years ago.

成功繁殖的最早和最普遍的障碍之一是多精受精，即多个精子使卵子受精。为了防止这些多余的受精，卵子进化出了多种机制。最近有人提出，哺乳动物卵子在受精时释放的锌可能会阻止额外的精子进入。在这里，我们证明两栖类和硬骨鱼的卵也释放锌。使用非洲爪蟾作为模型，我们记录了锌可逆地阻止受精。最后，我们证明细胞外锌同样会破坏不同门的卵的早期胚胎发育，包括刺胞动物门、棘皮动物门和脊索动物门。我们的研究表明，保护人类卵子免遭多个精子受精的基本策略可能在 6.5 亿年前就已进化。