Comprehensive DescriptionRead full entry
This large genus of labrids has only two representatives in the western Atlantic: the widespread Bluehead Wrasse Thalassoma bifasciatum and its Brazilian relative T. noronhanum. Several more species are found in the eastern Pacific and many others are native to the Indo-Pacific. The larvae of Pacific species are almost identical to the larval T. bifasciatum described below, but are missing the patch of melanophores at the front of the dorsal fin. Although usually described as having no melanophores, many larval Thalassoma I have collected in the Pacific Ocean have the same small melanophores along the edge of the membranes of the dorsal and anal fins and upper and lower membranes of the caudal fin as are found on larval T. bifasciatum. Note however, that only larvae in particularly good condition will have intact edges of the membranes.
Edge melanophores on a T. grammaticum larva, 13.0 mm SL, Clipperton Island.
Description: Body relatively thin, narrow, and long with a large eye and a terminal, small mouth. Pectoral fins medium, reach to vent. Pelvic fins very short. Dorsal and anal-fin bases long, caudal peduncle short and relatively wide. Melanophores limited to the fin-ray membranes, in a group along the first two or three dorsal-fin spines and then on the membrane fringes along the dorsal, anal, and caudal fins. Series of larvae show development of the eye from vertically oval to round (round in many larvae captured over the reef). Transitional recruits develop a prominent black spot on the front of the dorsal fin, a wide black stripe along the side from nose to tail and a dorsal stripe from the top of the head along the base of the dorsal fin. Transitional recruits on the reef commonly show remnants of the melanophores on the fin-membrane edges characteristic of the larvae.