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Thalassoma bifasciatum
Physical Description Bluehead wrasses have long, semi-cylindrical or cigar-shaped bodies. Their scales are round and flat. They have a pointed snout, and the mouth contains teeth. Their size and color, however, depend on whether they are terminal phase males, initial phase males, or females. Terminal phase (TP) males, also known as "supermales," have blue heads and green bodies. Three stripes (black, white, and black again) divide the colors of the head and body. Terminal phase males measure about 70 to 80 mm in length while initial phase males are approximately 60 mm. Initial phase (IP) females and males are colored in two different ways. One type has a yellow upper half of the body followed by a slight green/black area and then a white lower half. Females and initial phase males are also known to be white both above and below the dark area. This type of coloration is found in fish that primarily inhabit inshore regions. A dark spot is found on the anterior dorsal fin of both types of females and initial phase males. It should also be noted that females and initial phase males have the ability to change into terminal phase males and this switch includes a change of size and coloration. In addition, once there is a transformation from female or initial phase male to terminal phase male, the change is permanent.
Tom Owens Cay, Belize
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