The Female-to-Male Sex Change in the Japanese Angelfish
Commonly referred to as Japanese Angelfish, Centropyge interrupta (Perciformes - Pomacanthidae) is a colorful reef fish native to the southern and central Japan, and the northwestern Hawaiian Islands (Midway and Kure).
Centropyge interrupta is a protogynous hermaphrodite (meaning that they start they adult live as females and can switch to male under certain conditions). This fish lives in a harem social structure with one dominant male and from one to four females per reproductive unit. When the dominant male disappears from a harem, the largest female may change sex. In this species the sex reversal is completed in 20-39 days. In this case, the sex change is socially controlled.
The sex change (sequential hermaphroditism) is a widely documented phenomenon in plants and animals; and the protogynous hermaphroditism (female-to-male sex change), is well known among reef fishes, and even more, both-ways sex change (or bi-directional sex change) has been reported from several polygynous species of some fish families such as Gobiidae and Pomacanthidae.
References: [1] - [2] - [3]
Photo credit: ©Tanaka Juuyoh | Locality: Kashiwajima Kohchi-ken Prefecture, Japan (2006)