Barbel

Barbels are fleshy, elongated protrusions containing both mechanoreceptors (detecting water movement) and taste receptor cells (chemoreceptors), allowing fish to taste their environment by touch. Catfish species may have up to eight barbels arranged around the mouth, providing a nearly 360-degree gustatory map of the substrate. The common carp has four barbels; the Mekong giant catfish has none — barbel number and position are taxonomically diagnostic. Some deep-sea fish have luminescent barbels that function as lures rather than sensory organs.