Washington, February 12 : Researchers at the University of Washington, Seattle, have discovered that oysters have exotic sex lives, with females and males producing thousands of types of eggs and sperm.
Oysters begin their lives as a male and release vast numbers of sperm, which compete to fertilise the 100 million eggs that older, female oysters produce annually.
Lead researcher Stevan Springer says that oysters are different from many species that have diverse ornamentations and behaviours that help males show off, and females choose a suitable mate.
According to the researcher, this diversity results from an evolutionary 'battle of the sexes'.
Generally, males put in a lot of effort to woo females, and that latter invest time and energy in choosing a high-quality mate.
Pacific oysters, however, have a diverse range of proteins on the surfaces of their sperm and eggs, which " take the place of the behavioural mechanisms that act in other organisms," says Springer.
The researcher says that oysters cloud the water with millions of eggs and sperm.
He says that the diversity of sperm and egg fertilisation proteins results from the way that eggs prevent more than one sperm from entering, which can kill the resulting embryo.
Rather than accepting the first sperm to arrive, oyster eggs constantly evolve to all be slightly different, which cuts the proportion of sperm that are compatible with a given egg and prevents multiple fertilisations.
"Similar kinds of protein interactions alter sperm-egg compatibility in all sexual organisms, something to ponder the next time you enjoy oysters with a potential mate," he says.
The study has been reported in the Proceedings of The National Academy of Sciences.