Sexual Conflict and Seminal Fluid Proteins: A Dynamic Landscape of Sexual Interactions

Abstract

Sexual reproduction requires coordinated contributions from both sexes to proceed efficiently. However, the reproductive strategies that the sexes adopt often have the potential to give rise to sexual conflict because they can result in divergent, sex-specific costs and benefits. These conflicts can occur at many levels, from molecular to behavioral. Here, we consider sexual conflict mediated through the actions of seminal fluid proteins. These proteins provide many excellent examples in which to trace the operation of sexual conflict from molecules through to behavior. Seminal fluid proteins are made by males and provided to females during mating. As agents that can modulate egg production at several steps, as well as reproductive behavior, sperm “management,” and female feeding, activity, and longevity, the actions of seminal proteins are prime targets for sexual conflict. We review these actions in the context of sexual conflict. We discuss genomic signatures in seminal protein (and related) genes that are consistent with current or previous sexual conflict. Finally, we note promising areas for future study and highlight real-world practical situations that will benefit from understanding the nature of sexual conflicts mediated by seminal proteins.

Sexual Conflict in Hermaphrodites

“…Seminal-fluid-mediated effects are increasingly recognized as a common source of sexual conflict (see Sirot et al 2014), also in simultaneous hermaphrodites, as originally predicted by Charnov (1979). For example, seminal fluid investment (as indicated by variation in prostate gland size) covaries with female reproductive tract morphology among opisthobranch sea slugs in a manner consistent with sexually antagonistic coevolution .…”

Genomic responses to the socio-sexual environment in male Drosophila melanogaster exposed to conspecific rivals

“…For example, throughout the animal kingdom, seminal fluid typically contains multiple proteases, protease inhibitors, lipases, lectins, and CRISPs (Ravi Ram and Wolfner 2007). Many of the genes that encode these components evolve extremely rapidly and hence Sfp genes often lack orthologs even among very close relatives (Sirot et al 2014). …”

Sexual Conflict and Evolutionary Psychology: Towards a Unified Framework

“…A particular focus of interest has been the actions of the seminal fluid proteins, the nonsperm components of the male ejaculate (Chapman 2001;Ram and Wolfner 2007;Sirot et al 2014;Wolfner 2002). There are over 100 such proteins and peptides in the D. melanogaster male, and they are an extraordinarily diverse group of compounds in terms of structure and function (Mueller et al 2004(Mueller et al , 2005.…”