Bluehead wrasse

The bluehead wrasse or blue-headed wrasse (Thalassoma bifasciatum) is a species of saltwater fish in the wrasse family (Labridae) of order Perciformes native to the coral reefs of the tropical waters of the western Atlantic Ocean. Individuals are small (less than 110 mm standard length) and rarely live longer than two years. They form large schools over the reef and are important cleaner fish in the reefs they inhabit. The bluehead wrasse is found in coral reefs of the Atlantic Ocean. Its main range includes the Caribbean Sea and the southeast area of the Gulf of Mexico. Young/small females and males have yellow upper bodies and white lower bodies, often with green or black lateral stripes and occasionally dark vertical bars. This coloration is known as the initial phase. They 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. This color phase gives the species its name. Terminal phase males are larger (70 to 80 mm) than the initial phase males (60 mm). The bluehead wrasse forages for zooplankton, mollusks, and other small crustaceans, as well as parasites on other fish. Initial phase males eat primarily zooplankton from currents, and females and initial phase males have certain hunting times during the day. Though bluehead wrasses are common cleaner fish in the coral reefs they inhabit, they avoid cleaning piscivores such as the spotted moray, the graysby, and the red hind. Such species will view them as prey, but will not view gobies, another kind of cleaner fish, as prey. Other predators include the greater soapfish, roughtail stingray, and the trumpetfish. A significant parasite of bluehead wrasses is the intracellular myxozoan Kudoa ovivora, which can be found in the ovaries of female bluehead wrasses. Infected eggs are sterile and are also larger than uninfected eggs, and contain more organic and inorganic material. This implies the parasite causes a shift in resources from the mother to the eggs and decreases the fitness of the mother. Infected bluehead wrasses have been found to change sex earlier than uninfected females, possibly in response to the parasite. The bluehead wrasse is widespread in the northwestern Atlantic region and is one of the most abundant species in coral reefs near Puerto Rico, the Virgin Islands, and the Netherlands Antilles. It is listed under Least Concern. However, this species shows high site fidelity, so coral reef destruction could cause local endangerment. Due to its bright coloration, it is sometimes collected for the aquarium trade, but this is not a threat to the species. Like many other wrasse species, the bluehead wrasse is a protogynous sequential hermaphrodite; individuals may begin life either as males or females, but females can change sex later in life and become males.