Two Types of Lateral Line Afferents in the Eel (Anguilla anguilla)

The spontaneous and evoked discharges of eel lateral line sensory organs have been investigated. Each afferent nerve fibre has a well defined punctate receptive field, corresponding to a single canal organ. No axons were found to innervate more than one of these. All afferents pass through the Rarnus lat. dors. N.X. to the medulla oblongata. No peripheral unidirectional synapses exist in the nerve. Afferent axons are myelinated and belong to a large calibre (mode 12 μm) and a small calibre (mode 3 μm) axonal population in the nerve. The nerve contains about 800 myelinated axons at the level of its medullary entry, subserving approximately 100 sensory organs. In both groups rates of spontaneous discharge range from 0 c/s‐50 c/s. Both groups include extremely mechano‐sensitive units, and less sensitive units. The main difference between the slowly and rapidly conducting units is the more regular spontaneous firing pattern of the former group.