Atlantic Salmon Eggs Favour Sperm In Competition That Have Similar Major Histocompatibility Alleles

There is good evidence that increased variability in Major Histocompatibility (MH) genes, which are part of the immune system's recognition processes, allow an individual to be more effective at combating pathogens. Not surprisingly, therefore, mechanisms within reproduction (such as active mate choice) are known that promote MH genetic variability.

We examined whether similar mechanisms exist within sperm-egg compatibilities in Atlantic salmon. Using in vitro fertilization protocols, we replicated sperm competition experiments, in which sperm from male pairs were competed for different females' eggs. Within each male pair, one was similar to the female in MH genes, and the other dissimilar (and this treatment was then reciprocated with an MH-different female).

Contrary to expectations, we found a significant fertilization advantage for sperm from males that were similar at MH immunity genes.

This mechanism might result from selection for local adaptation in salmon, or mechanisms of fertilization could use immunorecognition to avoid hybridisation with genetically-different sperm.


Proceedings of the Royal Society B: Biological Sciences

Proceedings B is the Royal Society's flagship biological research journal, dedicated to the rapid publication and broad dissemination of high-quality research papers, reviews and comment and reply papers. The scope of journal is diverse and is especially strong in organismal biology.