There's a joke lost in translation somewhere isn't there?
I forget the name of it, but there is a movie set in the Roman Empire. If I recall correctly, there is a scene where a Senator asks someone that works under him of he liked snails or oysters. The implication is that snails were men\boys and oysters women\girls. He was being hit on, as such relationships were common.
My memory doesn't stretch back 25+ years well for a movie I saw once in Latin class. Now, the author may not be directly referencing this movie, but something else referencing it, or possibly something the movie referenced.