"Unlike in plants, selection during the haploid (gametic) phase of the life cycle has been assumed to be insignificant in animals. The main reason for this assumption is that gene expression in mature sperm was thought to be absent due to the densely packed nuclear DNA. However, there is increasing evidence that several genes are indeed expressed in mature sperm and hence may be under selection. Importantly, gene expression in mature sperm may lead to antagonistic selection between haploid and diploid phases, if the fitness effects of an allele are divergent in the two phases. The aim of the proposed project is to assess (i) the importance of haploid gene expression for sperm form and function and (ii) the existence of antagonistic selection between haploid and diploid life phases in animals. I will combine two important tools of evolutionary biology, namely experimental evolution and functional genomics to address these two questions. I will use the zebrafish Danio rerio as a study system, which is ideal because its entire genome is sequenced, many genes are annotated and it has external fertilization allowing in vitro fertilization assays. Allelic polymorphism will be estimated by assessing single nucleotide polymorphisms (SNPs) and will be linked with variation in sperm form (morphometry) and function (motility and longevity). The project will be hosted by Professor Göran Arnqvist and will be in collaboration with Professor Hans Ellegren, both at the Centre of Evolutionary Biology (EBC), University of Uppsala, Sweden. The EBC hosts one of the largest accumulations of evolutionary biologists in the world, and it provides an extremely active and simulating research atmosphere. The proposed project will allow me to establish myself as an independent researcher and will be an imperative stepping stone for my future career."