The Harlequin Sweetlips is an unusual looking fish. All the way from juvenile to adulthood it is very unique in its colouring and behaviours. We see it at various dive sites here on Koh Tao, White rock, Hin Pee Wee, Laem Thian, Junkyard, and many more.
The sweetlips belongs to the Haemulidae family, which includes other sweetlips and grunts, named for their ability to produce a grunting noise by grinding their teeth. The adult is mostly white covered with black spots and markings with yellowish colouring over its back and head. They are characterised by the huge lips, hence the name sweetlips.
Their young look completely different from their adult counterparts. The young are oranges and brown with large white spots. They have rounded fan-like fins which help with their very unique movements. The juvenile moves in erratic, jerky and random directions, it constantly looks like it doesnt know where its going or what its doing. The bright colours and these movemets are supposed to be a mimicry of a poisonous flatworm to deter wouldbe predators from eating the young fish so it can then grow up. As this then happens the juveniles colouring starts to get darker and darker with black spots starting to develop within the white spots. Their movements become less erratic and more subdued and they eventually look just like their parents. If you look for it however, you can still see the shadowy clusters on the adults, outlining where their big white spots used to be on their little orange bodies.