Fishes exhibit two broad categories of locomotion: body caudal fin locomotion and median-paired fin locomotion. One of the best-studied unsteady behaviours that fishes perform is the fast start. Fast starts can be initiated either by the reticulospinal neurons or by the Mauthner neurons to escape predators and catch prey. Motor neurons send signals to the muscles to coordinate muscle contraction, which leads to locomotion. Anguilliform locomotion, used by long, thin fishes, usually has a specific wavelength of less than one with a relatively large lateral amplitude along most of the body. Fin motions often change depending on swimming speed, and individuals can switch between pectoral fin, median fin, and body and caudal fin use as required. Median and paired fin swimming modes are generally classified by the group of animals that tend to demonstrate the behaviour. Most fishes have two sets of paired fins, the pectoral and the pelvic fins, and three median fins, the dorsal, anal and caudal fin.