Postcopulatory sexual selection (PCSS), comprised of sperm competition and cryptic female choice, has emerged as a widespread evolutionary force among polyandrous animals. There is abundant evidence that PCSS can shape the evolution of sperm. However, sperm are not the whole story: they are accompanied by seminal fluid substances that play many roles, including influencing PCSS. Foremost among seminal fluid models is Drosophila melanogaster, which displays ubiquitous polyandry, and exhibits intraspecific variation in a number of seminal fluid proteins (Sfps) that appear to modulate paternity share. Here, we first consolidate current information on the identities of D. melanogaster Sfps. Comparing between D. melanogaster and human seminal proteomes, we find evidence of similarities between many protein classes and individual proteins, including some D. melanogaster Sfp genes linked to PCSS, suggesting evolutionary conservation of broad-scale functions. We then review experimental evidence for the functions of D. melanogaster Sfps in PCSS and sexual conflict. We identify gaps in our current knowledge and areas for future research, including an enhanced identification of PCSS-related Sfps, their interactions with rival sperm and with females, the role of qualitative changes in Sfps and mechanisms of ejaculate tailoring.

This article is part of the theme issue ‘Fifty years of sperm competition’.

交配后性选择 (PCSS) 包括精子竞争和神秘的雌性选择，已成为一妻多夫动物中普遍存在的进化力量。有大量证据表明 PCSS 可以影响精子的进化。然而，精子并不是全部：它们伴随着具有多种作用的精液物质，包括影响 PCSS。在精液模型中最重要的是黑腹果蝇，它显示出无处不在的一妻多夫，并且在许多精液蛋白 (Sfps) 中表现出种内变异，这些蛋白质似乎调节了亲子关系。在这里，我们首先整合有关D. melanogaster Sfps身份的当前信息。D. melanogaster之间的比较和人类精液蛋白质组，我们发现了许多蛋白质类别和单个蛋白质之间相似性的证据，包括一些与 PCSS 相关的黑腹果蝇Sfp 基因，表明大规模功能的进化保守。然后我们回顾了D. melanogaster Sfps 在 PCSS 和性冲突中的功能的实验证据。我们确定了我们当前知识和未来研究领域的差距，包括对 PCSS 相关 Sfps 的增强识别、它们与竞争对手精子和女性的相互作用、Sfps 质量变化的作用和射精剪裁机制。

本文是“精子竞赛五十年”主题刊的一部分。