Every clownfish starts as male
Clownfish are protandrous hermaphrodites. Juveniles mature as males. The dominant fish in a group becomes the female.
Established2 min read
A group is a size queue. The biggest is female, the next is the breeding male, the rest are nonbreeders waiting. Remove the female and the male’s gonads reorganise. He becomes she. The next in line becomes him. Fricke and Fricke described the dominance rule in Amphiprion in 1977.
Sex here is a social fact with an anatomical consequence, not a chromosome assigned once. The fish is not confused. The hierarchy is the sex-determination system.
Caveats
- This is clownfish and their relatives, not all reef fish. Wrasses often go the other way, female to male.
Sources
- 1Fricke H., Fricke S.. Monogamy and Sex Change by Aggressive Dominance in Coral Reef Fish. Nature 266, 1977.