"Rage-Induced Color Change: The Phenomenon of Provoked Fish Turning Black"

Dominant male celebes medaka fish in Indonesia turn black during periods of heightened aggression, using their distinctive black markings as a signal of dominance to other fish. The black markings quickly emerge at the start of a conflict and are more likely to attack and less likely to be attacked. The color change phenomenon is likely facilitated by neurotransmitters on cells containing pigment granules, and similar changes are seen in other fish species. This signaling may be more about access to territory and resources than mating rights, and the speed of color change is controlled by factors such as neural stimulation and hormonal control.