Only some of the Mexican Mollies have mustaches, and when researchers looked into it, they found that mustached Mollies are considered more appealing by the female Mollies.
Unlike most species of fish, where the female lays eggs and the male comes along and fertilizes them later, Mollies live in places with a lot of predators, so fertilization is done internally. Translation: this fish have sex.
Not only do female Mollies like spending more time near male Mollies with mustaches, but it was also observed that male Mollies use their facial hair to give…. mustache rides. They literally tickle the female Mollies’ genitalia with their ‘staches.