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

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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”).