Prozac entering waterways is changing how fish behave and reproduce, study says - Prolonged exposure may change fish’s ability to adapt to environmental challenges and threaten their survival ...

Instead, they have modified a fin into a penetrating organ called a gonopodium. These penis-ish organs are tipped with an unpleasant set of claws, hooks ridges and spines.

Strictly speaking a gonopodium is not a penis. However, the larger this male reproductive organ is in one fish species leads to bigger brains in females.