Post-ejaculatory environmental effects on sperm phenotype and reproductive fitness in a broadcast spawning marine invertebrate

The post-ejaculatory environment, i.e., either in the female reproductive tract for internal fertilisers or in an external medium for external fertilisers, can be very hostile for sperm cells. I investigated a range of interacting physical and biological environmental factors to provide a detailed exploration of how interacting environmental conditions in the post-ejaculatory environment impact sperm functioning and fertilisation outcomes in a broadcast spawning marine mussel. My findings highlight the importance of considering the effects of environmental factors such as sperm density, sperm age, and, critically, female reproductive fluids for assessing sperm form and function.