Distribution and innervation of lateral line organs in the channel catfish.

The lateral line system of the channel catfish is formed by mechanoreceptive neuromasts located within five pairs of cephalic and one pair of trunk canals, as well as superficial lines of neuromasts, termed accessory and/or pit lines. Five pairs of pit lines occur on the head, and three pairs of superficial lines occur on the trunk. In addition to these mechanoreceptors, which are found in most teleost fishes, catfish also possess a total of over 4000 electroreceptive ampullary organs scattered over the entire body. The lateral line receptors are innervated by five pairs of lateral line nerves whose rami are secondarily associated with facial and trigeminal fibers that innervate taste buds and the dermis of the skin, respectively. The neuromasts of the trunk canal and the ramules of the posterior lateral line nerve that innervate them seem to be organized in a segmental pattern. The same is true for the intervertebral ramules of the recurrent facial ramus, which innervate the external taste buds on the trunk. The fibers of the gustatory and lateral line systems may use the neural crest, the developing spinal nerves, or both, to establish this segmental pattern. In this context, it may not be surprising that there is an intimate relationship among each of the sensory systems in the trunk.