Levitan D R
Am Nat. 1993 Apr;141(4):517-36. doi: 10.1086/285489.
Interspecific variation in egg size of marine invertebrates has been previously explained by a trade-off between gamete quality and quantity: the production of many small eggs with high mortality or fewer large eggs that develop quickly and experience reduced planktonic mortality. This theory assumes 100% fertilization of eggs and predicts that either strategy results in a similar number of settling offspring per unit of energy invested in reproduction. Empirical support for the theory has been equivocal. Here I offer an alternative hypothesis: larger eggs present a larger target for sperm and thus are fertilized at a higher rate. This theory suggests a trade-off between the production of many small eggs with a low probability of fertilization or fewer large eggs with a higher probability of fertilization. This hypothesis is tested with three congeneric sea urchins, Strongylocentrotus purpuratus, Strongylocentrotus franciscanus, and Strongylocentrotus droebachiensis, with a fivefold difference in egg volume. Species with larger eggs are fertilized at a higher rate and, if one assumes an equal allocation of resources, produce at least as many zygotes as species with smaller, more numerous eggs. This alternate hypothesis can explain continuous variation in egg size between species and provides a strong link between larval and adult life histories.
要么产生许多死亡率高的小卵，要么产生数量较少但发育迅速且浮游期死亡率较低的大卵。该理论假定卵的受精率为100%，并预测这两种策略每投入单位繁殖能量所产生的定居后代数量相似。对该理论的实证支持一直存在争议。在此，我提出另一种假设：较大的卵为精子提供了更大的目标，因此受精率更高。该理论表明在产生许多受精概率低的小卵或较少受精概率高的大卵之间存在权衡。用三种同属的海胆——紫海胆、加州紫海胆和球海胆进行了检验，它们的卵体积相差五倍。卵较大的物种受精率更高，并且，如果假设资源分配相等，那么与卵较小且数量较多的物种相比，至少能产生同样多的受精卵。这种替代假设可以解释物种间卵大小的连续变化，并在幼体和成年生活史之间建立了紧密联系。
