Lateral Line System

The lateral line system consists of water-movement-sensitive sensory organs in the epidermis of cyclostomes, fishes (Chondrichthyes, Osteichthyes), and aquatic stages of all three orders of amphibians. The phylogenetic origin of this system is not known. Already the oldest known ancestors of the modern fishes, the ostracoderms, probably possessed a lateral line system. At least twice during evolution part of this system evolved to an electrosensitive system, possibly by reduction of mechanical sensitivity and enhancement of electrical sensitivity of the sense organs. Like the labyrinth, the lateral line system derives from dorsolateral placodes.