Male, female, or both? When it comes to sex, fishes do it all!

If you can think of anything involving sex, from group sex to monogamy for life to males with penises on their heads, you can probably find good examples in fishes. Here I want to focus on a particularly interesting and bizarre aspect of fish sexual life: sex changing! Hermaphroditism (the expression of both female and male reproductive organs in the same individual) in fishes can occur in many ways, but most commonly, a fish starts off as one sex, and changes to the other at a certain stage in life (sequential hermaphroditism). A change from female to male is called protogyny (from the Greek “proto” = “first” and “gyno” = “female”), and a change from male to female is called protandry (from the Greek “proto” = “first” and “andros” = “male”).