In Vitro Fertilization Experiments Using Sockeye Salmon Reveal That Bigger Eggs Are More Fertilizable Under Sperm Limitation

Theory and evidence show that egg size evolves to optimise offspring and maternal fitness. However, an additional theory invokes sperm limitation as an important force, if increasing egg size acts as a bigger target for fertilization when gamete encounter rate is diluted.



We test this theory using in vitro fertilization experiments in externally-fertilizing sockeye salmon, where there is considerable variation in ovum size.



By subjecting egg batches of varying sizes to sperm-limitation, we discovered that bigger eggs were preferentially fertilized.



Thus, some element of egg size variation in fish could be selected for by fertilization demands under sperm limitation.


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 the journal is diverse and is especially strong in organismal biology.


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