Functional and Evolutionary Genetics of Seminal Fluid

• Applicant: Dr. Steven Ramm
• Subject Area: Reproductive Medicine, Urology ; Evolution, Anthropology
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 240721607

In addition to sperm, the male ejaculate typically contains a complex suite of other components that are transferred to the female reproductive tract at the time of mating. These ejaculate components are known collectively as seminal fluid, and are produced in the prostate and other accessory reproductive glands. Because seminal fluid-mediated effects on female reproductive physiology and behaviour could have profound consequences for determining male reproductive success, the study of seminal fluid has become a central concern of sexual selection and sexual conflict research. Nevertheless, despite the presumed importance of seminal fluid in the fields of reproductive and evolutionary biology, there are currently very few experimental systems where it has been feasible to systematically study seminal fluid function and evolution. Here I propose a multi-disciplinary research programme to establish the role of seminal fluid components in the free-living, simultaneously hermaphroditic flatworm genus Macrostomum. The programme aims to test the working hypothesis that post-mating sexual selection is a major force shaping seminal fluid function and evolution. I will also test unique predictions about seminal fluid that apply to simultaneous hermaphrodites. Specifically, I will begin by ranking seminal fluid candidate genes for functional characterization in M. lignano, on the basis of existing RNA-Seq data and a novel in situ hybridization screen to test for prostate-specific expression. For prioritised candidates with confirmed prostate-specific expression, I will then perform a series of RNAi knockdown experiments combined with fitness and detailed functional assays. Third, I will assess intraspecifc variation in seminal fluid production in M. lignano, to test for genetic, environmental and gene x environment effects on seminal fluid investment. Fourth, by performing interspecific transcriptomic experiments, I will compare seminal fluid complements across species, testing for lineage-specific bouts of adaptive evolution and uncovering the evolutionary consequences of two very different mating behaviours (reciprocal copulation vs. hypodermic insemination) exhibited by these flatworms, which should create radically contrasting selection regimes on seminal fluid. By revealing how male reproductive traits evolve under post-mating sexual selection and how seminal fluid functions to promote fertility, the results of the project will have broad implications for evolutionary and reproductive biology.

• DFG Programme: Research Grants