Neuromast organ, lateral line system. Apical surface of neuromast organ of lateral line system in a 17-day-old zebrafish, imaged by scanning electron micrograph. The hair bundles at the top of each sensory "hair" cell emerge through a pore in the skin (picture width 52.8 um). Movement of the surrounding water deflects the hair bundle, stimulating the hair cell. Fish (and aquatic amphibian larvae) use such info to detect presence of other fish or avoid predators. All vertebrate inner ears that detect sound vibrations and are similar to the hair cells of neuromast organs. Supplied by Andrew Forge, courtesy of Wellcome Images.