This herbivorous fish uses its strong beak-like mouthparts to scrape algae and other plant matter from the surface of the coral (4). This maintains the health of the reef by keeping algae in check, which could otherwise overwhelm the delicate reef ecosystem (5).
An unusual feature of parrotfishes is that they are able to change sex, with females becoming fully functional males (4). In a population, rainbow parrotfish start off as either females or males (known as primary males). Females may at some point in their life become male (secondary males). Populations that have these two types of males are called ‘diandrous’, meaning ‘two-males’ (4). A terminal phase male defends a territory and a harem of females. If the male should die, the most dominant female will become the dominant male, her ovaries becoming functional male testes (4).