Nature is amazing.
The bluehead wrasse is a fish that lives in small social groups in coral reefs in the Caribbean. Only the male has a blue head – signalling his social dominance over a harem of yellow-striped females.
If this male is removed from the group, something extraordinary happens: the largest female in the group changes sex to become male. Her behaviour changes within minutes. Within ten days, her ovaries transform into sperm-producing testes. Within 21 days she appears...