How about this - doubles their chances of a date on Saturday Night:-
Oysters are marine bivalves that live on the bottom of the ocean by cementing themselves permanently to a hard surface. They do not actually mate as most terrestrial animals do. Instead, oysters broadcast their gametes in the water, and fertilization takes place outside of their bodies. Oysters also have two separate sexes, males and females. However, oysters can completely change their sex between mating seasons! Juvenile oysters usually mature as males first and then change to females later in life. Occasionally, one oyster can function as both female and male at the same time, a condition known as hermaphroditism.