Role of protein phosphorylation/dephosphorylation in fish sperm motility activation: State of the art and perspectives

In many fish species, the spermatozoa are immotile in the testes and seminal plasma, and motility is induced when they are released in the aqueous environment. Extracellular factors control the activation of the axoneme through signal transduction across the plasma membrane. The present review examines the existing literature concerning the axoneme activation in fish, with particular emphasis on the role played by the protein phosphorylation/ dephosphorylation process, since post-transciptional modifications are involved in the mechanisms of sperm motility activation in many animals with external fertilization (starfish, sea urchins, sea cucumber, fish). We report the current understanding of the role played by the changes of protein phosphorylation state in sperm motility activation of teleost fish and provide additional tools for evaluating the gamete quality before and after cryopreservation procedure and, therefore, improve fish farm management. Statement of relevance: The present review examines the existing literature concerning the signaling pathways involved in the axoneme activation in fish, in order to better understand the molecular mechanism regulating spermmotility initiation and to show how the proteins that change their phosphorylation status after spawning can be used as biomarkers for sperm quality and cryodamage.