Lips are soft folds around the mouth. They are well developed in gobfish, carp, and sturgeon fish; some have no or poorly developed lips (shuka); the perch has them only on its lower jaw. They perform tactile and gustatory functions, contribute to a stronger capture of prey. In fish, the lips are usually replete with gustatory and tactile organs, and help capture prey. Fish may have normal or thickened lips, depending on their eating habits and diet.
The shape of each lip as well as the teeth reflect the eating habits of the fish. As a rule, both upper and lower lips are extremely thin, and in some cases completely absent. Apparently, thick fleshy lips do not play a significant role in the feeding process, but they are mainly observed in fish extracting food (both herbivorous and carnivorous) from the substrate. The lips are mainly used for plucking and scooping up food. Cheiloprion labiatus is the fish with the largest lips.