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The blue-headed wrasse (Thalassoma bifasciatum) is a species of saltwater fish in the wrasse family (family Labridae) of order Perciformes native to the coral reefs of the Caribbean Sea. Blueheads are small (less than 90 mm standard length) and rarely live longer than 2 years. They form large schools over the reef and feed primarily on planktonic copepods as well as small benthic crustaceans.
Like many other wrasse species, the bluehead is a protogynous sequential hermaphrodite: individuals begin life as either male or female, but females can change sex later in life and function as males. Females and young males are yellow and white in color, often with black lateral stripes and occasionally dark vertical bars. This coloration is known as the Initial Phase. These individuals can rapidly alter the presence or intensity of their yellow color, stripes, and bars, and these color changes appear to correspond to behavioral changes. Large females and some males can permanently change coloration and/or sex and enter the Terminal Phase coloration, which has a blue head, black and white bars behind the head, and a green body. It is this color phase that gives the species its name. One Terminal Phase male wrasse will usually coexist along with a group of roughly a dozen females; if the male dies, the largest female will transform, over a week, into a male, changing colour and behaviour to act as the new male over the remaining females.
[edit] References
- Thalassoma bifasciatum (TSN 170568). Integrated Taxonomic Information System. Accessed on 30 January 2006.
- "Thalassoma bifasciatum". FishBase. Ed. Ranier Froese and Daniel Pauly. 10 2005 version. N.p.: FishBase, 2005.
- Munday, P.L., P.M. Buston, and R.R. Warner, Diversity and flexibility of sex-change strategies in animals. Trends in Ecology and Evolution, 2006. 21(1): p. 89-95.
- Warner, R.R., Large mating aggregation and daily long-distance spawning migrations in the bluehead wrasse, Thalassoma bifasciatum. Environmental Biology of Fishes, 1995. 44: p. 337-345.
- Warner, R.R. and L.M. Dill, Courtship displays and coloration as indicators of safety rather than of male quality: the safety assurance hypothesis. Behavioral Ecology, 2000. 11(4): p. 444-451.
