Certain East African male cichlids, a kind of freshwater fish, have evolved a really odd way to increase their little sperms' chance of reproductive success. The game plan goes as follows:
Females of these species lay their eggs before they're fertilized and then gobble them up and store them in their mouths to keep them safe.
The males need to get their sperm into an egg-filled mouth to have fish babies. It might work if they just put flung their sperm out there in the water near a female, but that's a bit of a shot in the dark (water).
So the males' anal fins have evolved to have spots that look like cichlid eggs. The females (displaying the notorious fish intelligence) think the spots are their own eggs, so they come over to eat 'em.
The males then squirt out their sperm, which the females unintentionally gobble down, thinking maybe they're eating their own eggs.
How long before teachers and parents start adding these East African cichlids to their explanations to young 'uns about the birds and bees?