In the classic theory of sexual roles, females are more careful in their choice of a mate because their reproductive investment is relatively higher. However, increasing evidence shows that males can also be choosy. Mate choice can be based on physical characteristics, such as body size and color ornaments, which have been documented as factors that also influence the maintenance of polymorphism. Here, we experimentally tested whether males of the annual killifish Millerichthys robustus preferentially choose females according to variations in ocelli number on the base of the caudal fin, or according to body size, in classical dual decision experiments. We demonstrated that there is a strong preference of the males of M. robustus for females with greater numbers of ocelli on the base of the caudal fin (females with 5–7 versus 1–2 ocelli) and for females of larger body size. We also tested whether female body size or number of ocelli are linked to higher fecundity or increased egg size, quantifying the number of embryos produced by the females of each experimental group and measuring the size of their eggs. Our results revealed that large females with more ocelli produced more and larger eggs than large females with fewer ocelli, and than small females regardless of the number of ocelli. These results may suggest that males of M. robustus that choose large-sized females can mate with genetic quality in parameters directly related to biological success, such as higher egg production of large-sized eggs. This is probably related to a higher hatching percentage, and larger subsequent larvae with rapid growth rates. We therefore propose that large body size and high number of ocelli on the base of the caudal fin in females could have evolved through male mate choice.

在经典的性角色理论中，女性在选择配偶时更加谨慎，因为她们的生殖投资相对较高。然而，越来越多的证据表明，男性也可能很挑剔。配偶的选择可以基于物理特征，例如体型和颜色装饰，这些已被记录为也会影响多态性维持的因素。在这里，我们实验测试是否每年鳉鱼的雄性壮体米氏鰕鳉根据尾鳍的基础，或根据车身尺寸，在经典双决策实验对单眼数变异优先选择女性。我们证明了M.robustus的雄性有强烈的偏好对于尾鳍基部有更多单眼的雌性（雌性有 5-7 个对 1-2 个单眼）和体型较大的雌性。我们还测试了雌性体型或 ocelli 的数量是否与更高的繁殖力或增加的卵子大小有关，量化每个实验组的雌性产生的胚胎数量并测量其卵子的大小。我们的结果表明，无论单眼数目多少，具有更多单眼的大型雌性比单眼较少的大型雌性产卵更多、更大，并且比小型雌性产卵更多、更大。这些结果可能表明M.robustus 的雄性选择大型雌性的雌性可以在与生物学成功直接相关的参数中与遗传质量交配，例如大型鸡蛋的产蛋量更高。这可能与较高的孵化率以及随后的幼虫较大且生长速度较快有关。因此，我们提出，雌性尾鳍基部的大体型和大量单眼可能是通过雄性配偶选择进化而来的。